Bruce Lange's comments regarding COX-2 selective NSAIDs are quite correct and readers would be well advised to add this addendum to Table 5.1
Strictly speaking, radiocontrast agents are diagnostic tools and not drugs and therefore were not included in this article on safe drug prescribing. However, radiocontrast agents certainly can cause nephrotoxicity in patients with renal insufficiency. I do not think that the current published studies regarding the use of N-acetylcysteine in patients with renal insufficiency have conclusively established that this drug absolutely reduces the incidence of contrast nephropathy.2 Because N-acetylcysteine is relatively harmless, I think that it is being used widely without adequate data.
Malvinder Parmar's comments regarding morphine dosage adjustments are quite correct when morphine is used on a regular basis. However, when morphine is used on a sporadic basis, as in postoperative pain control, I do not believe that dosage adjustment is practically required. Dosage adjustments are required when morphine is used on a regular basis such as in a palliative care setting (as reflected in Table 4).
An excellent review article by Song and White states that angiotensin receptor blockers do not require dosage adjustment in patients with renal insufficiency.3 This includes candesartan cilexetil. Furthermore, a subsequent article by See and Stirling extensively reviewed the pharmocokinetics of candesartan cilexetil and did not find a significant alteration in patients' blood pressure response (in those with renal insufficiency) after they received multiple doses of candesartan cilexetil .4
As the treatment of many nonemergent conditions does not require an immediate or maximal drug response, I would hope that clinicians would start drugs at the lowest convenient dose, regardless of renal function, and increase to produce the desired response.
Joanne Elaine Kappel Department of Nephrology St. Paul's Hospital of Saskatoon Saskatoon, Sask.
References
- 1.Kappel J, Calissi P. Nephrology: 3. Safe drug prescribing for patients with renal insufficiency. CMAJ 2002;166(4):473-7. [PMC free article] [PubMed]
- 2.Tepel M, van der Giet M, Schwartzfeld C, Laufer U, Liermann D, Zidek W. Prevention of radiographic-contrast-agent-induced reductions in renal function by acetylcysteine. N Engl J Med 2000; 343:180-4. [DOI] [PubMed]
- 3.Song JC, White CM. Pharmacologic, pharmacokinetic, and therapeutic differences among angiotensin II receptor antagonists. Pharmacotherapy 2000;20(2):130-9. [DOI] [PubMed]
- 4.See S, Stirling AL. Candesartan cilexetil: an angiotensin II-receptor blocker. Am J Health Syst Pharm 2000;57:739-46. [DOI] [PubMed]