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British Journal of Clinical Pharmacology logoLink to British Journal of Clinical Pharmacology
. 2011 Nov;72(5):787–797. doi: 10.1111/j.1365-2125.2011.04019.x

Drug−disease interaction: Crohn's disease elevates verapamil plasma concentrations but reduces response to the drug proportional to disease activity

Forough Sanaee 1, John D Clements 1, Alistair W G Waugh 2, Richard N Fedorak 2, Richard Lewanczuk 3, Fakhreddin Jamali 1
PMCID: PMC3243013  PMID: 21592185

Abstract

AIM

Inflammation is involved in the pathogenesis of cardiovascular diseases that includes reduced response to pharmacotherapy due to altered pharmacokinetics and pharmacodynamics. It is not known if these effects exist in general in all inflammatory conditions. It also remains unknown whether in a given population the effect is a function of disease severity. We investigated whether pharmacokinetics and pharmacodynamics of a typical calcium channel inhibitor are influenced by Crohn's disease (CD), a disease for which the disease severity can be readily ranked.

METHODS

We administered 80 mg verapamil orally to (i) healthy control subjects (n = 9), (ii) patients with clinically quiescent CD (n = 22) and (iii) patients with clinically active CD (n = 14). Serial analysis of verapamil enantiomers (total and plasma unbound), blood pressure and electrocardiograms were recorded over 8 h post dose. The severity of CD was measured using the Harvey-Bradshaw Index.

RESULTS

CD substantially and significantly increased plasma verapamil concentration and in a stereoselective fashion (S, 9-fold; R, 2-fold). The elevated verapamil concentration, however, failed to result in an increased verapamil pharmacodynamic effect so that the patients with elevated verapamil concentration demonstrated no significant increase in response measured as PR interval and blood pressure. Instead, the greater the disease severity, the lower was the drug potency to prolong PR interval (r = 0.86, P < 0.0006),

CONCLUSIONS

CD patients with severe disease may not respond to cardiovascular therapy with calcium channel blockers. Reducing the severity increases response despite reduced drug concentration. This observation may have therapeutic implication beyond the disease and the drug studies herein.

Keywords: calcium channels, Crohn's disease, inflammation, PK−PD relationship, receptor down regulation, reduced response

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

  • Inflammatory conditions such as Crohn's disease are associated with cardiovascular complications. Inflammation also substantially reduces clearance of some cardiovascular drugs. It has also been shown that in rheumatoid arthritis, an elevation in verapamil concentration does not result in increased response.

WHAT THIS STUDY ADDS

  • A reduced response upon increased verapamil concentration in another inflammatory condition, inflammatory bowel disease, with different aetiology from arthritis was found. Interestingly, however, a mere affliction with the disease is not sufficient to alter pharmacokinetics and pharmacodynamics since we found that the alteration is a function of disease severity. There is a remarkable reverse correlation between the disease severity and response to verapamil. Our observation suggests a complex relationship between pharmacokinetics and pharmacodynamics which may have implications beyond the disease and the drug studied herein.

Introduction

Inflammation is associated with cardiovascular complications. Indeed, the survival of post myocardial infarction patients and the risk of in-hospital coronary events for unstable angina correlate well with the degree of inflammation measured as the concentrations of pro-inflammatory mediators such as C-reactive protein [1] and interleukin-6 [2]. Furthermore, the prevalence of cardiovascular complications is much greater in patients with rheumatoid arthritis than in the general population [3]. Similarly, inflammatory bowel disease (IBD) including Crohn's disease appears to influence the cardiovascular system, although an increased risk has not been consistently demonstrated [4–10]. This effect of inflammation has not been fully investigated but may be associated with altered effectiveness of cardiovascular therapy as a consequence of a disease−drug interaction.

Inflammation also influences action and disposition of drugs including some of the cardiovascular agents that are commonly used by patients with inflammatory conditions. It is known to result in elevated plasma concentrations of drugs that are efficiently metabolized in the liver [11–13]. Verapamil is such a drug with low bioavailability due to its efficient first pass hepatic metabolism. It is, therefore, expected for plasma verapamil concentrations to be greater in patients with inflammatory conditions when compared with otherwise healthy individuals. Such elevated concentrations may have both therapeutic and toxic consequences. However, previous studies have demonstrated that inflammatory conditions such as rheumatoid arthritis [14], old age [15] and obesity [16, 17] result in altered response to verapamil despite substantially increased plasma concentrations. Furthermore, it has been shown in humans and animal models that the pharmacological response to calcium [14, 18] and potassium [19] channel blockers as well as β-adrenoceptor antagonists [20, 21], but not angiotensin II inhibitors [22], is reduced by inflammation. This reduced response has not been investigated in IBD which, although an inflammatory condition, has its own aetiology.

The dual effect of inflammation does not seem to be limited to cardiovascular drugs since an elevated drug concentration that is not accompanied with increased effect has very recently been reported for midazolam in critically ill children [23]. This observation has also been linked to inflammation.

Interestingly, the action and disposition of verapamil is restored in patients whose rheumatoid arthritis is in remission [24] pointing to the possibility that the degree of the disease severity may have a role in this observation. Herein, we report the pharmacokinetics and pharmacodynamics of verapamil in IBD (Crohn's disease), a condition for which a convenient and relatively robust method exists for grading of the disease severity [25]. Due to its inflammatory nature, Crohn's disease is expected to alter both drug plasma protein binding and the hepatic metabolism of certain drugs, resulting in reduced clearance [26–28]. The effect of the disease on response to cardiovascular drugs is, however, unknown.

Following therapeutic doses, verapamil causes negative dromotropic effects reflected as a plasma concentration-dependent prolongation of PR interval and AV node block [29], indicative of L-type calcium channels function. The PR interval prolongation is conveniently detectable even after small single doses [30]. Hence, the response to the drug, as a typical reflection of the blockade of L-type calcium channels, is readily measurable even in normal subjects. The main objective of the study was to examine the effect of disease severity on the action and disposition of an efficiently metabolized drug.

Methods

Chemicals

Apo-verapamil 80 mg tablets were purchased from the University of Alberta Hospital Pharmacy (Edmonton, Alberta, Canada). Verapamil hydrochloride, aspergillus nitrate reductase (10 U ml-1), heptafluorobutanol, FAD, NADPH, pyruvic acid, sulphanilamide, (+)-glaucine, lactic dehydrogenase (1500 U ml−1) and naphthylethylenediamine dihydrochloride were purchased from Sigma-Aldrich Chemical Canada (Oakville, ON, Canada). High-performance liquid chromatography (HPLC) grade hexane and HPLC grade isopropanol, triethylamine and 98% ethanol were purchased from Caledon Laboratories (Georgetown, Canada). HEPES was purchased from Fisher Biotech (Edmonton, AB, Canada).

Study design and patients

This was a single centre, single treatment, healthy volunteer controlled study. The protocol was approved by the University of Alberta Health Research Ethics Board and was conducted in accordance with the Declaration of Helsinki. The study was registered in the Northern Alberta Clinical Trials and Research Centre. All participants provided written informed consent. A baseline electrocardiogram (ECG) was performed to ensure that there were no underlying cardiac abnormalities. Three groups of subjects were enrolled: (i) healthy volunteers (control, n = 9), (ii) patients with quiescent Crohn's disease (CD remission, n = 22) and (iii) patients with active Crohn's disease (CD active, n = 14).

Subjects were 18 to 69 years of age, male or female of non-childbearing potential and non-smokers for at least 6 months before entry into the study. Subjects with illness other than Crohn's disease within 30 days prior to the study were excluded. Subjects were informed that they should not ingest grapefruit juice or any new prescription or over-the-counter medications for at least 7 days prior to the study. They were, however, permitted to continue, unchanged, their Crohn's disease medications. All patients completed a Harvey-Bradshaw Index (HBI) questionnaire [25] as a validated clinical assessment of Crohn's disease activity. The HBI is a cumulative score of the domains of general well being, abdominal pain, number of liquid or soft bowel motions and extra-intestinal manifestations. A HBI score of 0 to 4 indicates clinical remission, 5 to 7 mild disease, 8 to 16 moderate disease and above 16 severe disease.

The disease category of the subjects was kept from workers who carried out the pharmacokinetic and pharmacodynamic experiments.

Drug administration and pharmacokinetic/pharmacodynamic sampling

Subjects fasted overnight for at least 8 h prior to taking a single 80 mg verapamil tablet by mouth with 200 ml of water. An intravenous line was inserted for blood sampling, and the patient was allowed to rest recumbent for 30 min prior to measuring baseline physiologic variables. A standard meal was provided 3 h post dose and subjects were free to drink water throughout the study. Blood samples (3 ml) were taken at 0 (pre dose), 20, 40 min and 1, 2, 3, 5, 6.5 and 8 h for verapamil concentration analysis.

For electrocardiogram (ECG) recording, a standard lead 1 and aV5 electrocardiogram was recorded using a Holter monitor (Hewlett-Packard, Avondale, PA). The mean of five PR intervals and heart rate measurements were recorded during the minute before blood sample collection for the pharmacokinetic analysis. Mean arterial pressure (MAP), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using an HDI/Pulsewave Cardiovascular Profiling Instrument CR-2000 (Hypertension Diagnostics Inc, Minneapolis, Minn). The experimentally observed maximum percentage effects were recorded.

Two patients with active disease were brought back after approximately 4 months and re-examined for their HBI score and response to verapamil. Our aim was to test whether a change in the disease activity resulted in a proportionally altered responsiveness to the drug. Only the results from the first examination were included in our statistical evaluations.

Protein binding

Serum for the protein binding study was pooled from the time 0 h blood sample of all three groups (n = 5/group). The pooled serum was adjusted to pH 7.4 with 0.1 m HCl. The serum was then spiked with 100 ng ml−1 of racemic verapamil. Samples were incubated at 37°C for 1 h and then transferred to micropartition chambers (Amicon Division of W.R. Grace & Co, Danvers MA) for ultrafiltration. The chambers were centrifuged at 2000 g for 1 h. In addition, eight chambers were loaded with phosphate buffer, pH 7.4, to determine the presence of any nonspecific binding or adsorption to the micropartition system. Both filtrate and non-filtrate concentrations were measured and the fraction unbound (fu) determined as the unbound concentration divided by total concentration. To ensure concentrations were above the minimum quantifiable limit for the HPLC assay, four micropartitions of the 12 chambers were pooled allowing for a total of three measurements per group.

Stereospecific verapamil assay

A previously described stereospecific HPLC method [31], as later modified [32] was used to determine plasma concentrations of R- and S-verapamil. The assay was precise (CV < 10%) and accurate (error < 10%) at the minimum quantifiable enantiomer concentrations of 5 ng ml−1. We did not have access to norverapamil, a major metabolite of verapamil found in plasma with much less pharmacological activity than the parent compound [33]. Instead of concentration, therefore, we examined the area of the eluted HPLC peaks. The order of appearance and retention time of norverapamil enantiomers were known to us from previous studies [14].

Inflammatory biomarkers assays

Nitrites were analyzed in the pre dose serum samples indirectly by measuring the concentration of its stable breakdown product serum nitrite through using a previously described method [34, 35]. Serum C-reactive protein was determined in the pre dose blood sample at the University of Alberta Hospital using the Dade-Behring (Deerfield, Ill) assay kit.

Data analysis and statistics

Data are presented as means ± SD. Pharmacodynamic responses including changes in systolic and diastolic blood pressure, heart rate and PR interval were measured based on observed differences between baseline and post-treatment values. The area under the percentage effect−time curve (AUEC) was measured using the linear trapezoidal rule.

Pharmacokinetic metrics included the observed maximum plasma concentration (Cmax) and the time of its attainment (tmax) as well as the area under the plasma drug concentration−time curve until the last experimental data point (AUC) calculated using the linear trapezoidal rule. The terminal elimination rate constant was calculated for those subjects who exhibited a log-linear terminal phase with at least three usable experimental points. A non-weighted nonlinear least-squares regression was used.

The relationship between the PR interval and plasma S-verapamil concentrations was explored using WinNonlin 4.1 (Pharsight). Mean S-verapamil concentration and percent change from baseline in PR interval data were fitted to a series of PK/PD models. The final exposure−response plot was created using S-Plus 8.1 (TIBCO Spotfire, Somerville, MA).

The significance of the differences was tested using one way anova with the Duncan Multiple Range ad hoc test at α = 0.05.

Results

Subjects' characteristics

The baseline demographic information of subjects is shown in Table 1. Subjects in the CD remission group were on the following medications: infliximab (n = 6), methotrexate (n = 2), azathioprine (n = 7), lorazepam (n = 1), 5-ASA (n = 4), oral contraceptive (n = 1), felodipine (n = 1), prednisone (n = 1) and amitriptyline (n = 1). Patients in CD active group were taking methotrexate (n = 2), azathioprine (n = 6), levothyroxine (n = 1), 5-ASA (n = 1), hyoscine (n = 1), metronidazole (n = 2), ciprofloxacin (n = 4), morphine (n = 1), citalopram (n = 1), folic acid (n = 1), cholestyramine (n = 1), prednisone (n = 1), premarine (n = 1), topiramate (n = 1), infliximab (n = 1) and certilizumaband (n = 1). Patients in the control group were on no medications.

Table 1.

Subjects' characteristics

Control (n = 9) Crohn's disease remission (n = 22) Crohn's disease active (n = 14)
Age (years) 34.9 ± 18.6 38.4 ± 14.9 33.7 ± 11.7
Gender M/F 3/6 9/13 5/9
Body mass index (kg m−2) 24.3 ± 1.6 23.9 ± 1.5 26.4 ± 1.7
Baseline SBP (mmHg) 117 ± 14 113 ± 11 109 ± 9.7
Baseline DBP (mmHg) 66 ± 13 66 ± 8.9 63 ± 6.6
Baseline HR (beats min−1) 63 ± 9.1 61 ± 9.5 67 ± 8.7
HBI score 0.00 2.16 ± 2.09 10.79 ± 6.48*
PR interval (ms) 159 ± 20 155 ± 20 136 ± 33
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*

Significantly different from other groups (P < 0.05); SBP, systolic blood pressure; DBP diastolic blood pressure; HR, heart rate; HBI, Harvey Bradshaw Index.

There were no significant differences between the three groups in terms of age, weight, height, baseline blood pressure, heart rate or PR interval.

Inflammatory biomarkers

The concentrations of serum nitrite and C-reactive protein were numerically higher in patients with active Crohn's disease compared with patients with Crohn's disease in remission and healthy controls. The differences, however, did not reach statistical significance due to a great inter-subject variability particularly among the patients with active disease (Figure 1).

Figure 1.

Figure 1

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Mean (±SD) of pro-inflammatory mediators measured in the three groups of subjects (control, Crohn's disease remission, Crohn's disease active). The means were not significantly different

Verapamil pharmacokinetics

The effect of active disease on pharmacokinetics of verapamil was stereoselective. Plasma S-verapamil concentration in patients with active Crohn's disease was significantly higher than in both healthy controls and patients in Crohn's disease in remission (Figure 2, Table 2). AUC was increased 9- and 14-fold in patients with active Crohn's disease when compared with Crohn's disease patients in remission and controls, respectively (P < 0.001). With respect to R-verapamil, although both mean Cmax and AUC values were greater in patients with active Crohn's disease as compared with the other groups, the differences did not reach statistical significance.

Figure 2.

Figure 2

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Plasma verapamil enantiomers concentration−time curves following single oral doses of 80 mg racemic verapamil in three groups of subjects. Control (Inline graphic); Remission (Inline graphic); Active (Inline graphic)

Table 2.

Pharmacokinetics of S- and R- verapamil, PR prolongation and changes in blood pressure following single doses of 80 mg to healthy control and Crohn's patients in remission or with active disease

Verapamil enantiomer Control (n = 9) Crohn's disease remission (n = 22) Active (n = 14)
tmax (min)
 S 60 (40–60)a 60 (40–60)a 60 (40–120)a
 95% CI 0.74, 1.46 0.81, 1.33 0.57, 1.83
 R 60 (20–60)a 60 (40–60)a 60 (20–60)a
 95% CI 0.60, 0.88 0.79, 1.21 0.67, 1.93
Cmax (ng ml-1)
 S 19.9 ± 10.5a 39.3 ± 51.6a 189.7 ± 243.1b
 95% CI 13.0, 26.8 17.7, 60.9 62.0, 317
 R 278 ± 127a 353 ± 313a 558 ± 538b
 95% CI 195, 361 222, 484 271, 840
t1/2 (h)
 S 4.33 ± 1.93a 3.56 ± 1.55a 17.0 ± 22.7b
(n = 4) (n = 11) (n = 11)
 95% CI 2.44, 6.22 2.64, 4.48 3.59, 30.41
 R 3.16 ± 1.04a 3.13 ± 1.23a 3.13 ± 1.54a
(n = 9) (n = 22) (n = 13)
 95% CI 2.48, 3.84 2.62, 3.64 2.29, 3.97
AUC (ng ml-1 h)
 S 61.7 ± 46.8a 95.5 ± 140.7a 537 ± 598b
 95% CI 31.1, 92.3 36.71, 154.3 222, 849
 R 723 ± 453a 720 ± 755a 1714 ± 1693a
 95% CI 427, 1019 396, 1044 827, 2601
PR interval prolongation
 % max/baseline 21.4 ± 14.9a 14.8 ± 9.8a 17.0 ± 17.0a
 95% CI 11.7, 31.1 10.7, 18.9 2.86, 31.1
 AUEC, %.h 44.3 ± 45.1a 36.0 ± 41.4a 32.2 ± 67.8a
 95% CI 14.8, 73.8 18.7, 53.3 −3.32, 67.7
Blood pressure (%)
 Systolic 13.4 ± 10.0a 10.8 ± 4.4a 12.2 ± 7.5a
 95% CI 6.87, 19.9 8.96, 12.6 8.17, 16.2
 Diastolic 12.6 ± 3.5a 9.4 ± 3.0a 9.9 ± 3.6a
 95% CI 10.3, 14.9 8.15, 10.7 8.01, 11.8
Heart rate (%) 11.3 ± 5.8a 10.9 ± 5.3a 9.6 ± 5.0a
 95% CI 7.51, 15.1 8.69, 13.1 6.98, 12.2
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Different characters in the row indicate significant difference at α = 0.05. Blood pressure (mmHg) and heart rates are changes from baseline. Experimental points from fewer patients were used to calculate t1/2 due to fluctuation. Data are presented as mean ± SD except for Cmax, t1/2 and AUC that are geometric means ± SD and tmax is median (range).

The ratios of HPLC peak areas of both S and R norverapamil over their corresponding verapamil enantiomers were not significantly different among the three groups of subjects at any measured time point.

There was no significant difference in the fraction of protein unbound drug between the controls (S 0.11 ± 0.02; R 0.051 ± 0.009) and patients with Crohn's disease in remission (S 0.073 ± 0.02; R 0.041 ± 0.01). However, as compared with controls, patients with active Crohn's disease had significantly reduced unbound fraction of S and R enantiomers (0.050 ± 0.011 and 0.020 ± 0.007, respectively).

The t1/2 of the log-linear portion of the plasma drug concentration curve was not calculated for all subjects due to fluctuations in concentration (Figure 2). Nevertheless, while the t1/2 was significantly and substantially prolonged for S-verapamil, that of R-verapamil remained unchanged (Table 2).

Verapamil pharmacodynamics

Except for the patients with high HBI scores, all subjects responded to verapamil by demonstrating reduced systolic and diastolic blood pressure, heart rate and PR prolongation (Figure 3, Table 2). The observed marked increased S-verapamil concentrations in the patients with active disease did not result in greater response as the mean pharmacodynamic parameters remained at the same level as those calculated for control and remission groups (Table 2). Furthermore, with regard to the PR interval, there was a strong significant negative correlation between the maximum percent change from baseline (P = 0.0006) or AUEC (P = 0.035) and H-B score (Figure 4). Patients with high H-B index demonstrated little or no response. A significant association between the disease activity and response to verapamil was absent in the CD remission group. No other pharmacokinetic or pharmacodynamics indices demonstrated significant correlation with disease severity.

Figure 3.

Figure 3

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PR interval prolongation−time profiles following single oral doses of 80 mg racemic verapamil in three groups of subjects. Error bars represent SD. Control (Inline graphic); Remission (Inline graphic); Active (Inline graphic)

Figure 4.

Figure 4

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The effect of disease severity on PR interval prolongation in response to single oral doses of 80 mg racemic verapamil administered to patients with active Crohn's disease. The data present the observed maximum values (A) or the area under effect−time curves (AUEC) (B). Patients who were tested twice in 4 months are shown with symbols that are different from others. The first test is donated by ▴ and ▾ while the second tests are denoted by ○ and □, respectively. The data from the second evaluations were not included in the statistical analysis

Counter-clockwise hystereses were observed for the plasma S-verapamil concentration-PR interval prolongation relationship in some but not all individual subjects, indicating a time delay between the plasma concentrations and cardiovascular response. When the concentration−effect data from each group were pooled, the relationship between PR interval and verapamil concentration was best described by a simple linear relationship (Figure 5). Interestingly, the association between the mean values were significant for all groups (P < 0.05) with a slope for each group distinguishable from others. The group with active disease had the least steep slope and the greatest variability as compared with other two groups. Our attempt to calculate EC50 failed as the estimated values were much greater than the highest observed experimental data points.

Figure 5.

Figure 5

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The relationship between mean PR interval prolongation and mean S- plasma verapamil concentrations. Regression lines are the best estimate of the relationship between two variables. All relationships were significant (P < 0.05). Control, r = 0.9271 (□); Remission, r = 0.926 (▴); Active, r = 0.580 (○)

The HBI score in the two patients who were re-examined in 4 months had not substantially changed (HBI score: from 7 to 8 and from 12 to 11). However, their disease activity vs. verapamil responsiveness data fitted the general plot remarkably well (Figure 4).

Discussion

The effect of inflammatory conditions [12] including Crohn's disease on the disposition of drugs has been widely reported since the 1970 s [27]. It is generally believed that inflammatory conditions result in reduced drug clearance, thereby elevating concentrations of efficiently metabolized drugs [12, 27]. An increased drug concentration is alarming due to the possibility of increased undesirable effects. However, most studies have only examined the pharmacokinetics of drugs and hence their cautionary conclusions are usually without supporting pharmacodynamic data. The present data highlight, a few important points: First, affliction with IBD does not necessarily result in elevated drug concentrations. Indeed, plasma concentrations of verapamil, a typical drug with efficient hepatic metabolism, are not elevated in Crohn's patients whose disease has subsided to remission (Figure 2, Table 2). Verapamil concentrations elevate only when the disease is active. The second important point is that an elevated verapamil concentration does not necessary result in increased potency or toxicity. This is contrary to the general belief that a high drug concentration may result in increased potency. The third point is the interesting observation that reveals, for the first time, a strong association between the severity of an inflammatory condition and response to a cardiovascular drug; i.e. the greater the disease activity, the lower the response to verapamil (Figure 4). Indeed, the patients with HBI scores of greater than 12 demonstrated no or negligible PR prolongations in response to verapamil. This is while those with less disease activity still showed some response and patients in remission yielded the same pharmacodynamic and pharmacokinetic indices as did the healthy volunteers.

It is important to note that HBI reflects the patient's well-being and is not a direct measure of the severity of inflammation as its components include various symptoms such as pain, nature of stool and use of drugs. Hence, the observed reduced response to verapamil in patients with high HBI scores cannot be unequivocally attributed to the inflammation associated with the disease.

Although the mean pharmacological responses to verapamil were not significantly different among the examined groups, the slope of the mean changes in PR prolongations vs. S-verapamil concentrations was substantially steeper for healthy volunteers than those of other groups with that of the group in remission in between (Figure 5). This suggests yet another sign of the effect of disease severity that due to the associated great variability cannot be readily quantified.

The observed reduction in both clearance and pharmacological activity of verapamil is attributed to down regulation of target proteins, i.e. cytochrome P450 enzymes [34] and calcium channels [36], respectively. While the latter results in elevated drug concentrations, the former reduces the drug−receptor binding [18] to yield a reduced response. Since verapamil is a substrate for P-glycoprotein [37], the possibility of increased bioavailability stemming from an inflammation-induced down regulation of efflux protein [38, 39] also exists. Previous reports dealing with other forms of inflammatory conditions, have ruled out an association between the diminished response and a reduced unbound drug concentration secondary to an inflammation-induced elevated plasma protein responsible for verapamil binding [19]. Indeed, the present study confirmed that despite the observed 50% reduction in the fraction of the unbound drug caused by active Crohn's disease, the free drug concentration still remains substantially higher than normal due to the several fold increase in the total drug concentration. Nevertheless, in light of the observed reduced response in the tested patients reported herein one may conclude that the therapeutic consequence of the elevated concentration of certain cardiovascular drugs becomes moot or, at least, questionable. However, other effects, unrelated to the blocking of the calcium channels, may emerge in response to high concentrations.

The mechanism involved in the down regulation of these target proteins is not quite clear. However, elevated expression of pro-inflammatory mediators such as interlukin-6, tumour necrosis factor, angiotensin II and nitric oxides can, at least in part, be involved [40]. According to a recent report in an animal model of inflammation, an observed reduced responsiveness to the β-adrenoceptor blocker propranolol is associated with lower cardiac norepinephrine transporter concentration [41]. A reduction in the transporter, the primary component of norepinephrine uptake-1 that removes norepinephrine from neuronal junctions is closely related to a reduced β-adrenergic target protein. Excessive sympathetic nervous system innervation is a well-established component of inflammatory conditions [10, 42–44] that may be involved in the down regulation of the receptor. An altered sympathetic nervous system modulation in intestinal inflammation has been discussed in the literature, e.g. Straub et al. [45].

The changes in the disposition of norverapamil followed those of the parent drug as the ratios of HPLC response of the metabolite enantiomers over those of respective verapamil enantiomers remained unaffected by the disease. This indicates that the increased norverapamil concentration in the patients with active Crohn's disease as compared with other groups is secondary to the corresponding increase in verapamil concentration.

Increased NO is a reliable marker of inflammation in active rheumatoid arthritis [14]. We observed an increased mean concentration of nitrite, a stable metabolite of NO in our group with active Crohn's disease as comparedwith those in remission as well as the healthy control group. The differences among the three groups, however, did not reach the set significance level due, probably, to a great inter-subject variability associated with the latter group (Figure 1). This was expected due to the substantial variability in the disease severity (Figure 4). A similar observation was made for C-reactive protein, another marker of inflammation in human which increases endothelial dysfunction and plays a role in the development coronary artery disease [2] (Figure 1).

Our data suggest that in assessing the effectiveness of cardiovascular drugs which are affected by inflammation, the severity of the condition must be considered regardless of the observed or expected plasma drug concentration. The disease severity can be controlled for Crohn's disease or rheumatoid arthritis. This will result in restoration of the function of the calcium channels. In obesity and old age, however, control of inflammation is not achieved as readily as in the mentioned diseases. Animal studies suggest that even under active conditions HMG-CoA reductase inhibitors [21] and angiotensin II receptor blockers [36] restore the diminishing effect of inflammation on response to verapamil and the β-adrenoceptor antagonist, propranolol, respectively. In addition, angiotnesin II blockers appear to maintain their effectiveness in active rheumatoid arthritis [22, 46] due, perhaps, to their anti-inflammatory effects [40]. These observations remain to be made in obese and elderly humans.

Patients with IBD are at least as prone to cardiovascular conditions as the general population [4–10]. The effectiveness of common cardiovascular classes of drug is, therefore, important when treating this category of patients. Accordingly, the observation that the pharmacodynamics and pharmacokinetics of verapamil, a representative of the L-type calcium channel antagonist class, has therapeutic relevance that extends beyond the drug used and the disease investigated herein.

Interestingly, greater than usual doses of alfentanil, a supplement to patients under nitrous oxide anaesthesia, are needed for patients with Crohn's disease due to lower threshold response [47]. The mechanism of this lower than usual response to alfentanil is unknown but is shown to be similar to verapamil at the level of pharmacodynamics.

The limitations of the present study include the fact that our subjects were normotensive. Nevertheless, we have shown that severe Crohn's disease may result in altered calcium channel function. It would be most interesting to examine the same effect in patients who actually need cardiovascular therapy. Our second limitation may be the fact that we made our observation only after single doses of verapamil. Our objective, however, was to see whether the response to verapamil, as a reflection of the function of the L-type calcium channels, was altered. This was achieved even after single doses by measuring PR interval prolongation caused by verapamil. The prolonging effect is a sensitive and concentration-dependent marker of calcium channel function and administration of single doses provides the necessary information [15, 16]. In addition, the lack of statistical significance between data generated from the three groups can be attributed to the limited number of subjects used in the study.

In conclusion, in patients with clinically active Crohn's disease, the drug potency is decreased despite an increase in the concentration of verapamil enantiomers. However, in patients who are in clinical remission, the pharmacokinetics and pharmacodynamics of verapamil return to normal. In addition, in the treatment of cardiovascular disease in patients with inflammatory conditions such as Crohn's disease, consideration should be paid to the activity of the disease and the degree of inflammation. It appears that for an effective control of cardiovascular conditions in patients with severe inflammatory diseases, curtailing of the inflammation is essential; treatments that include HMG-CoA reductase inhibitors and/or angiotensin interruption may be found useful. The present observation may have clinical implications beyond the tested drug and the selected disease as it may be extrapolated to other inflammatory diseases. Evidence of similar observations involving other drugs or different diseases have started to emerge [23, 47].

Acknowledgments

This study was supported in part by the Canadian Foundation for Innovations through the Centre of Excellence for Gastrointestinal Inflammation and Immunity Research, Alberta Heritage Foundation for Medical Research and the Heart and Stroke Foundation of Canada. JD Clements was a Canadian Institutes for Health Research Strategic Training Fellow in Tomorrow's Research Cardiovascular Health Professionals.

Competing Interests

There are no competing interests to declare.

REFERENCES

  • 1.Pietilä KO, Harmoinen AP, Jokiniitty J, Pasternack AI. Serum C-reactive protein concentration in acute myocardial infarction and its relationship to mortality during 24 months of follow-up in patients under thrombolytic treatment. Eur Heart J. 1996;17:1345–9. doi: 10.1093/oxfordjournals.eurheartj.a015068. [DOI] [PubMed] [Google Scholar]
  • 2.Biasucci LM, Liuzzo G, Fantuzzi G, Caligiuri G, Rebuzzi AG, Ginnetti F, Dinarello CA, Maseri A. Increasing levels of interleukin (IL)-1Ra and IL-6 during the first 2 days of hospitalization in unstable angina are associated with increased risk of in-hospital coronary events. Circulation. 1999;99:2079–84. doi: 10.1161/01.cir.99.16.2079. [DOI] [PubMed] [Google Scholar]
  • 3.Maradit-Kremers H, Nicola PJ, Crowson CS, Ballman KV, Gabriel SE. Cardiovascular death in rheumatoid arthritis: a population-based study. Arthritis Rheum. 2005;52:722–32. doi: 10.1002/art.20878. [DOI] [PubMed] [Google Scholar]
  • 4.Bragagni G, Brogna R, Franceschetti P, Zoli G. Cardiac involvement in Crohn's disease: echocardiographic study. J Gastroenterol Hepatol. 2007;22:18–22. doi: 10.1111/j.1440-1746.2006.04384.x. [DOI] [PubMed] [Google Scholar]
  • 5.Dagli N, Poyrazoglu OK, Dagli AF, Sahbaz F, Karaca I, Kobat MA, Bahcecioglu IH. Is inflammatory bowel disease a risk factor for early atherosclerosis? Angiology. 2010;61:198–204. doi: 10.1177/0003319709333869. [DOI] [PubMed] [Google Scholar]
  • 6.Dorn SD, Sandler RS. Inflammatory bowel disease is not a risk factor for cardiovascular disease mortality: results from a systematic review and meta-analysis. Am J Gastroenterol. 2007;102:662–7. doi: 10.1111/j.1572-0241.2006.01018.x. [DOI] [PubMed] [Google Scholar]
  • 7.Duricova D, Pedersen N, Elkjaer M, Gamborg M, Munkholm P, Jess T. Overall and cause-specific mortality in Crohn's disease: a meta-analysis of population-based studies. Inflamm Bowel Dis. 2010;16:347–53. doi: 10.1002/ibd.21007. [DOI] [PubMed] [Google Scholar]
  • 8.Jess T, Loftus EV, Harmsen WS, Zinsmeister AR, Tremaine WJ, Melton LJ, 3rd, Munkholm P, Sandborn WJ. Survival and cause specific mortality in patients with inflammatory bowel disease: a long term outcome study in Olmsted County, Minnesota, 1940-2004. Gut. 2006;55:1248–54. doi: 10.1136/gut.2005.079350. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Papa A, Santoliquido A, Danese S, Covino M, Di Campli C, Urgesi R, Grillo A, Guglielmo S, Tondi P, Guidi L, De Vitis I, Fedeli G, Gasbarrini G, Gasbarrini A. Increased carotid intima-media thickness in patients with inflammatory bowel disease. Aliment Pharmacol Ther. 2005;22:839–46. doi: 10.1111/j.1365-2036.2005.02657.x. [DOI] [PubMed] [Google Scholar]
  • 10.Smith CJ, Haire WD, Kaufman SS, Mack DR. Determination of prothrombin activation fragments in young patients with inflammatory bowel disease. Am J Gastroenterol. 1996;91:1221–5. [PubMed] [Google Scholar]
  • 11.Emami J, Pasutto FM, Jamali F. Effect of experimental diabetes mellitus and arthritis on the pharmacokinetics of hydroxychloroquine enantiomers in rats. Pharm Res. 1998;15:897–903. doi: 10.1023/a:1011928732588. [DOI] [PubMed] [Google Scholar]
  • 12.Morgan ET. Impact of infectious and inflammatory disease on cytochrome P450-mediated drug metabolism and pharmacokinetics. Clin Pharmacol Ther. 2009;85:434–8. doi: 10.1038/clpt.2008.302. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Roberts MS, Liu X, Zou Y, Siebert GA, Chang P, Whitehouse MW, Fletcher L, Crawford DH. Effect of adjuvant-induced systemic inflammation in rats on hepatic disposition kinetics of taurocholate. Am J Physiol Gastrointest Liver Physiol. 2011;300:G130–6. doi: 10.1152/ajpgi.00162.2010. [DOI] [PubMed] [Google Scholar]
  • 14.Mayo PR, Skeith K, Russell AS, Jamali F. Decreased dromotropic response to verapamil despite pronounced increased drug concentration in rheumatoid arthritis. Br J Clin Pharmacol. 2000;50:605–13. doi: 10.1046/j.1365-2125.2000.00314.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Abernethy DR, Wainer IW, Longstreth JA, Andrawis NS. Stereoselective verapamil disposition and dynamics in aging during racemic verapamil administration. J Pharmacol Exp Ther. 1993;266:904–11. [PubMed] [Google Scholar]
  • 16.Abernethy DR, Schwartz JB. Verapamil pharmacodynamics and disposition in obese hypertensive patients. J Cardiovasc Pharmacol. 1988;11:209–15. [PubMed] [Google Scholar]
  • 17.Hanafy S, Pinsk M, Jamali F. Effect of obesity on response to cardiovascular drugs in pediatric patients with renal disease. Pediatr Nephrol. 2009;24:815–21. doi: 10.1007/s00467-008-1064-y. [DOI] [PubMed] [Google Scholar]
  • 18.Sattari S, Dryden WF, Eliot LA, Jamali F. Despite increased plasma concentration, inflammation reduces potency of calcium channel antagonists due to lower binding to the rat heart. Br J Pharmacol. 2003;139:945–54. doi: 10.1038/sj.bjp.0705202. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Kulmatycki KM, Abouchehade K, Sattari S, Jamali F. Drug-disease interactions: reduced beta-adrenergic and potassium channel antagonist activities of sotalol in the presence of acute and chronic inflammatory conditions in the rat. Br J Pharmacol. 2001;133:286–94. doi: 10.1038/sj.bjp.0704067. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Guirguis MS, Jamali F. Disease-drug interaction: reduced response to propranolol despite increased concentration in the rat with inflammation. J Pharm Sci. 2003;92:1077–84. doi: 10.1002/jps.10381. [DOI] [PubMed] [Google Scholar]
  • 21.Clements JD, Jamali F. Pravastatin reverses the down-regulating effect of inflammation on beta-adrenergic receptors: a disease-drug interaction between inflammation, pravastatin, and propranolol. Vascul Pharmacol. 2007;46:52–9. doi: 10.1016/j.vph.2006.06.009. [DOI] [PubMed] [Google Scholar]
  • 22.Daneshtalab N, Lewanczuk RZ, Russell A, Jamali F. Rheumatoid arthritis does not reduce the pharmacodynamic response to valsartan. J Clin Pharmacol. 2004;44:245–52. doi: 10.1177/0091270003262951. [DOI] [PubMed] [Google Scholar]
  • 23.Vet NJ, de Hoog M, Tibboel D, de Wildt SN. The effect of critical illness and inflammation on midazolam therapy in children. Pediatr Crit Care Med. 2011;12:1–3. doi: 10.1097/PCC.0b013e3181fe406d. [DOI] [PubMed] [Google Scholar]
  • 24.Ling S, Lewanczuk RZ, Russell AS, Ihejirika B, Jamali F. Influence of controlled rheumatoid arthritis on the action and disposition of verapamil: focus on infliximab. J Clin Pharmacol. 2009;49:301–11. doi: 10.1177/0091270008328099. [DOI] [PubMed] [Google Scholar]
  • 25.Harvey RF, Bradshaw JM. A simple index of Crohn's-disease activity. Lancet. 1980;1:514. doi: 10.1016/s0140-6736(80)92767-1. [DOI] [PubMed] [Google Scholar]
  • 26.Belpaire FM, Bogaert MG. Binding of alfentanil to human alpha 1-acid glycoprotein, albumin and serum. Int J Clin Pharmacol Ther Toxicol. 1991;29:96–102. [PubMed] [Google Scholar]
  • 27.Schneider RE, Babb J, Bishop H, Hoare AM, Hawkins CF. Plasma propranolol levels in coeliac disease and Crohn's disease. Br Med J. 1976;2:1324. doi: 10.1136/bmj.2.6047.1324-b. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28.Waller DG, Smith CL, Renwick AG, George CF. Intravenous propranolol in patients with inflammatiom. Br J Clin Pharmacol. 1982;13:577–8. doi: 10.1111/j.1365-2125.1982.tb01426.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29.Thomas SH, Stone CK, Koury SI. Cardiac dysrhythmias in severe verapamil overdose: characterization with a canine model. Eur J Emerg Med. 1996;3:9–13. doi: 10.1097/00063110-199603000-00002. [DOI] [PubMed] [Google Scholar]
  • 30.Johnston A, Burgess CD, Hamer J. Systemic availability of oral verapamil and effect on PR interval in man. Br J Clin Pharmacol. 1981;12:397–400. doi: 10.1111/j.1365-2125.1981.tb01233.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31.Shibukawa A, Wainer IW. Simultaneous direct determination of the enantiomers of verapamil and norverapamil in plasma using a derivatized amylose high-performance liquid chromatographic chiral stationary phase. J Chromatogr. 1992;574:85–92. doi: 10.1016/0378-4347(92)80101-u. [DOI] [PubMed] [Google Scholar]
  • 32.Mehvar R, Reynolds J. Reversal of stereoselectivity in the hepatic availability of verapamil in isolated perfused rat livers. Role of protein binding. Drug Metab Dispos. 1996;24:1088–94. [PubMed] [Google Scholar]
  • 33.Neugebauer G. Comparative cardiovascular actions of verapamil and its major metabolites in the anaesthetised dog. Cardiovasc Res. 1978;12:247–54. doi: 10.1093/cvr/12.4.247. [DOI] [PubMed] [Google Scholar]
  • 34.Ling S, Jamali F. Effect of early phase adjuvant arthritis on hepatic P450 enzymes and pharmacokinetics of verapamil: an alternative approach to the use of an animal model of inflammation for pharmacokinetic studies. Drug Metab Dispos. 2005;33:579–86. doi: 10.1124/dmd.104.002360. [DOI] [PubMed] [Google Scholar]
  • 35.Grisham MB, Johnson GG, Lancaster JR., Jr Quantitation of nitrate and nitrite in extracellular fluids. Methods Enzymol. 1996;268:237–46. doi: 10.1016/s0076-6879(96)68026-4. [DOI] [PubMed] [Google Scholar]
  • 36.Hanafy S, Dagenais NJ, Dryden WF, Jamali F. Effects of angiotensin II blockade on inflammation-induced alterations of pharmacokinetics and pharmacodynamics of calcium channel blockers. Br J Pharmacol. 2008;153:90–9. doi: 10.1038/sj.bjp.0707538. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Cornwell MM, Pastan I, Gottesman MM. Certain calcium channel blockers bind specifically to multidrug-resistant human KB carcinoma membrane vesicles and inhibit drug binding to P-glycoprotein. J Biol Chem. 1987;262:2166–70. [PubMed] [Google Scholar]
  • 38.Schmith VD, Foss JF. Inflammation: planning for a source of pharmacokinetic/pharmacodynamic variability in translational studies. Clin Pharmacol Ther. 2010;87:488–91. doi: 10.1038/clpt.2009.258. [DOI] [PubMed] [Google Scholar]
  • 39.Uno S, Kawase A, Tsuji A, Tanino T, Iwaki M. Decreased intestinal CYP3A and P-glycoprotein activities in rats with adjuvant arthritis. Drug Metab Pharmacokin. 2007;22:313–21. doi: 10.2133/dmpk.22.313. [DOI] [PubMed] [Google Scholar]
  • 40.Dagenais NJ, Jamali F. Protective effects of angiotensin II interruption: evidence for antiinflammatory actions. Pharmacotherapy. 2005;25:1213–29. doi: 10.1592/phco.2005.25.9.1213. [DOI] [PubMed] [Google Scholar]
  • 41.Clements JD, Jamali F. Norepinephrine transporter is involved in down-regulation of beta1-adrenergic receptors caused by adjuvant arthritis. J Pharm Pharm Sci. 2009;12:337–45. doi: 10.18433/j3d012. [DOI] [PubMed] [Google Scholar]
  • 42.Evrengül H, Dursunoglu D, Cobankara V, Polat B, Seleci D, Kabukçu S, Kaftan A, Semiz E, Kilic M. Heart rate variability in patients with rheumatoid arthritis. Rheumatology International. 2004;24:198–202. doi: 10.1007/s00296-003-0357-5. [DOI] [PubMed] [Google Scholar]
  • 43.Härle P, Straub RH, Wiest R, Mayer A, Schölmerich J, Atzeni F, Carrabba M, Cutolo M, Sarzi-Puttini P. Increase of sympathetic outflow measured by neuropeptide Y and decrease of the hypothalamic-pituitary-adrenal axis tone in patients with systemic lupus erythematosus and rheumatoid arthritis: another example of uncoupling of response systems. Ann Rheum Dis. 2006;65:51–6. doi: 10.1136/ard.2005.038059. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Perry F, Heller PH, Kamiya J, Levine JD. Altered autonomic function in patients with arthritis or with chronic myofascial pain. Pain. 1989;39:77–84. doi: 10.1016/0304-3959(89)90177-2. [DOI] [PubMed] [Google Scholar]
  • 45.Straub RH, Wiest R, Strauch UG, Harle P, Scholmerich J. The role of the sympathetic nervous system in intestinal inflammation. Gut. 2006;55:1640–9. doi: 10.1136/gut.2006.091322. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46.Daneshtalab N, Lewanczuk RZ, Russell AS, Jamali F. Drug-disease interactions: losartan effect is not downregulated by rheumatoid arthritis. J Clin Pharmacol. 2006;46:1344–55. doi: 10.1177/0091270006292163. [DOI] [PubMed] [Google Scholar]
  • 47.Gesink-van der Veer BJ, Burm AG, Vletter AA, Bovill JG. Influence of Crohn's disease on the pharmacokinetics and pharmacodynamics of alfentanil. Br J Anaesth. 1993;71:827–34. doi: 10.1093/bja/71.6.827. [DOI] [PubMed] [Google Scholar]

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