Pill Shape Determines Esophageal Transit Times—A Pill‐to‐Pill Study

ABSTRACT

Objective

When manufacturing medications, several parameters are considered in pill design, particularly shape and size. We hypothesized that oval‐shaped pills would transit more quickly through the esophagus than round pills.

Methods

Esophageal transit time (pill) (ETTp) of round and oval barium dummy‐pills, derived from VFSS in 112 healthy individuals with no swallowing complaints and 50 individuals referred with swallowing complaints, was compared. ETTp was measured using quantitative software.

Results

ETTp differed significantly by shape. In healthy adults, median round (13 mm, 1 g) ETTp was 26.4 s (SD 23.6) compared to oval ETTp (13 mm long axis, 1 g) of 5.4 s (SD 4) [p < 0.001]. In those with swallowing complaints, round ETTp was 45 s (SD 44) vs. oval ETTp 9 s (SD 14) [p < 0.001]. Gender and age differed across groups, with normal oval pill swallowers younger and more likely to be female than those with swallow complaints (39 vs. 69 years, p < 0.001; 70% female vs. 31% female, p = 0.018).

Conclusions

Medication shape affects ETTp, with oval‐shaped pills traveling significantly faster through the esophagus than round pills. However, oval‐shaped pills do not highlight abnormality in the esophagus to the same degree as a round pill. Therefore, consideration of the purpose of pill administration during VFSS should guide pill shape choice, with round pills most suited for diagnostic testing. In a clinical setting, oval‐shaped medication should be favored, if possible, for those with compromised swallow ability.

Level of Evidence

3.

Shape of pills differ, affecting how easy it is to swallow them. We compared esophageal transit times of a round pill with an oval pill demonstrating in both healthy and symptomatic adults, that the oval pill demonstrated a significantly shorter transit time.

1. Introduction

Swallowing difficulty (dysphagia) is a common complaint presenting to both otorhinolaryngology (ORL) and speech‐language therapy (SLT) clinics. Patients may characterize their dysfunction in terms of what textures they are able to manage—solids versus liquids. Frequently, medications are problematic for those with swallowing impairment and in some cases, even for those with normal swallows! Medications are vital for many individuals but may be ineffective, partially active, or injurious to tissue if they become lodged in unintended locations. Liquid formulations often taste unpleasant and are not favored by consumers. Therefore, the swallowability of solid medications is a crucial aspect of pill manufacture and encompasses many different factors. Despite a wealth of information regarding these parameters in pharmaceutical manufacture, there is a lack of direct comparisons of different shaped pills and their esophageal transit times in humans. Previous studies have suggested that medication formulation can affect esophageal transit and pill stasis [1, 2]. Various medical comorbidities can prolong esophageal transit time compared to normal, even in the absence of primary esophageal pathology [3]. Medicines contain substances that may be harmful to esophageal mucosa, causing irritation, ulceration, or even perforation [2]. Given that medications are prescribed to individuals that have a medical indication, we need to understand pill transit in affected groups to minimize risks associated with pill stasis and to develop recommendations for medication formulation for patients with esophageal structural pathology or dysmotility.

Prior investigation of pill transit times has been undertaken through fluoroscopic means, usually testing round pills [1, 3, 4, 5, 6]. The purpose of administering these pills has been to identify luminal narrowing such as a stricture, and therefore a round‐shaped pill of known diameter (12–13 mm) is used [4]. However, round pills are often reported by patients to be difficult to manage or to get stuck during swallowing. Manufacturers now often shape medications with asymmetric axis lengths, to achieve an oval shape, which may allow for vertical orientation of the long axis of the pill during the swallow, improving ease of transit. However, literature is lacking that confirms that this shape configuration changes pill transit time.

The gold standard assessment of swallowing remains the VFSS. Fluoroscopy allows for quantitative measures to be derived, bringing reliability and accuracy to evaluation and treatment planning [6, 7]. Allen et al. showed that the addition of a 13‐mm round pressed barium pill to the VFSS protocol improved esophageal screening sensitivity from 62.8% to 71%, due to its ability to identify areas of non‐compliant narrowing < 13 mm in diameter [4]. Strictures or rings that measure less than 13 mm in diameter often result in food impaction and symptom complaint.

Normative data in esophageal screening has reported a mean ETT of 10.7 s for a 20 mL bolus, 25.3 s for a 13‐mm round pressed barium pill, and 28.6 s for paste in healthy adults across the lifespan [6]. Normative data assessment has also indicated in many cases that some degree of esophageal bolus and round pill stasis can occur in normal adults and that the pill may pause briefly at certain locations such as proximal to the aortic knuckle or proximal to the lower esophageal sphincter before passing into the stomach [6]. At present, there is no normative data to describe ETTp for oval‐shaped pills.

This study evaluated ETT of round and oval‐shaped pills (Figure 1) and their correlation with demographic information. Research questions included: (1) Are ETTp for oval pills different from round pills? (2) Is there a relationship between ETT for different shaped pills, that is, if one is prolonged, are both prolonged? (3) Do different‐shaped ETTp differ between asymptomatic compared to symptomatic adults? We hypothesized that the ETTp of oval pills would be faster than round pills.

FIGURE 1.

Photograph showing 13‐mm round barium pressed tablet, oval barium‐filled gelatine capsule alongside a ruler to indicate relative sizes. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]

2. Methods

This study received ethics approval (New Zealand Health and Disability Ethics Committee 13/STH/202 and University of Auckland Human Patients Ethics Committee 9263).

2.1. Participants

One hundred and twelve healthy adults were recruited from the community through local advertisement. Exclusion criteria included previous swallowing difficulties or any health condition known to disrupt swallowing function. All participants scored 0 on the Eating Assessment Tool (EAT‐10) [8]. Healthy participants were aged between 18 and 100 years and swallowed either a round or oval‐shaped pill during their VFSS.

Fifty patients consecutively referred for a VFSS at one regional hospital with symptoms including cough, globus, and solid food dysphagia between 2023 and 2025 were also recruited. Patient underlying aetiologies included those post‐treatment for head and neck cancer, treated Zenker's diverticuli, esophageal dysmotility, cervical osteophytosis, or plating. Patients were excluded if swallow study data was incomplete, that is, missing standardized coins/rings to allow for measurement calibration and those who did not swallow a pill. All patients were given both a round and oval‐shaped pill during the same study (in random order).

2.2. Videofluoroscopic Swallowing Study Protocol

VFSS in normal volunteers were performed in the Radiology suite, using a Videofluoroscope (Toshiba, Tokyo, Japan) and recorded at 30 frames per second onto a USB drive. Timing information was superimposed on the fluoroscopic recording in 100ths of a second using a Horita VS‐50 Video Stopwatch (Horita, Capistrano Beach, California). A 19‐mm diameter ring was taped to the participants neck, shoulder or chin within view of videofluoroscopic images for calibration. Symptomatic individual's studies were performed using a Videofluoroscope (Siemens Artis Zee Multi‐Purpose SN 15880) recorded at 30 frames per second using TIMS MVP. A 20 mm coin was taped to the participant's neck, shoulder, or chin within view of videofluoroscopic images. A standard VFSS protocol was used for all participants. After their lateral plane protocol (1, 3, 20, 100 mL Level 0 barium liquid [E‐Z Paque 96% w/v diluted to 19%], 5 mL paste [E‐Z‐paste 60% w/w]), participants were screened in an antero–posterior (AP) plane. Healthy participants swallowed 20 mL IDDSI 0 barium liquid, 5 mL barium paste and either a 1 mL barium‐filled gelatine oval capsule (24 mm length) or 13 mm round powder‐compressed barium tablet (EZ‐Disk, E‐Z‐Em Inc., NJ, USA) with a 100 mL water. Patients with swallow complaints were given both pill types in random order, each with a 100 mL swallow of water and taken one at a time. The individual was told to “swallow in one go” to avoid deglutitive inhibition. The pill was followed from the oral cavity to the stomach. Screening continued for 20 s following swallow initiation, if the capsule had not yet passed into the stomach at this stage screening was paused for 20 s and then resumed for a further 20 s. If the pill was still present, the participant was asked to take a dry swallow to see if clearance occurred. The screening was stopped at 60 s regardless of the position of the barium pill to limit radiation exposure in keeping with the local policy requirements.

2.3. Measures

Each videofluoroscopy was analyzed using real‐time and frame‐by‐frame viewing using Swallowtail analysis software (Bell Medical, St. Louis, Missouri, USA). ETTp was recorded in the AP view from the moment the capsule entered the upper esophageal sphincter to its entry into the stomach. Raters documented the location and time of capsule stasis.

2.4. Data Analysis

Statistical analysis was performed using IBM SPSS Statistics Version 23.0 (2013, Armonk, New York, USA). VFSS videos were analyzed by an ORL trainee, trained in using Swallowtail. To establish interrater reliability, 50% of the videos picked at random were assessed by two additional raters. The two raters comprised a speech‐language pathologist and fellowship‐trained laryngologist, both with research backgrounds and extensive experience in VFSS analysis. Inter‐rater reliability was substantial (ICC = 0.92, p < 0.001). T‐tests were used to assess differences in ETTp between pill types, gender, and patient versus healthy participants. Spearman's correlation was used to assess associations between age and ETTp. Sub‐group analyses of different aetiologies were not undertaken due to small group sizes. p < 0.05 was considered significant.

3. Results

One hundred and sixty‐two participants completed VFSS that included a barium dummy‐medication swallow. Ninety‐five healthy adults (48% female) swallowed a 13‐mm round pill, 17 healthy adults (70% female) swallowed a 24 mm‐long oval gel capsule (Figure 1) and 50 patients (30% female) swallowed both the 13‐mm round pill and the oval gel capsule on the same day (Table 1). There were differences in gender between groups (p = 0.007). Healthy participants swallowing the oval capsule were statistically younger than those swallowing the round pill (39 years [SD 16] vs. 58 years [SD 21], p < 0.001), and younger than patients (who were swallowing both pills) (39 years vs. 69 years [SD 12], p < 0.001) (Table 2).

TABLE 1.

Presenting diagnoses for patients undertaking dual pill swallowing.

Presenting diagnosis	Gastrointestinal	Head and neck cancer	Neurological (MND, CVA)	Respiratory	Other (spinal plate, osteophyte)
Percentage	51	34	6	3	6

Abbreviations: CVA—cerebrovascular accident; MND—motor neuron disease.

TABLE 2.

Pill esophageal transit times in healthy adults and adults with swallow complaints.

	Healthy capsule (n = 17)	Healthy round pill (n = 95)	Patient dual capsule (n = 50)	Patient dual round (n = 50)
ETT in s [SD]	5.4 [4]	26.4 [24]	9 [14]	45 [44]
Age a (years) [SD]	39 [16]	58 [21]	69 [12]	69 [12]
Gender a (Female)	70%	48%	31%	31%
t‐test	Healthy cap versus patient cap	Healthy round versus patient round	Healthy cap versus healthy round	Patient cap versus patient round
p value	0.3	0.002	0.0004	0.00001

Note: t‐test—Students t‐test, significant results are in italics.

^a Age and gender differed significantly across all three groups.

ETTp for each pill type in each group were calculated. In healthy adults, the mean ETTp of round pills (26.4 s [SD 23.6 s]) was statistically longer than the ETTp of oval gel‐capsules (5.4 s [SD: 4 s], p = 0.0004). Likewise, in patients (with swallow complaints) who swallowed both types of pills, there was also a significant difference in ETTp dependent on shape—round pill ETTp 45 s (SD: 44) vs. oval pill ETTp 9 s (SD: 14), (p < 0.00005) (Table 2).

Comparing each pill type between healthy and patient swallowers also demonstrated significant differences based on shape characteristics: round pills in healthy adults mean ETTp 26.4 s versus 45 s (patients) (p < 0.002), oval pills mean ETTp 5.4 s (normal) versus 9 s (patients) was not significantly different (p = 0.3).

Gender and age differed significantly across groups; however, in the subjects swallowing both round and oval pills at the same sitting, wherein gender and age are the same, there remained a significant difference in ETTp based on pill shape alone (round ETTp 45 s vs. oval ETTp 9 s; p < 0.00001).

4. Discussion

Our study compared ETT for barium‐filled oval gelatine capsules (24‐mm long axis) to round compressed powder pills (13‐mm diameter) (Figure 1). We measured ETTp in individuals with no swallowing complaints and also in patients referred for throat and swallowing issues, and found significant differences based on pill shape. Oval ETTp duration was markedly shorter than round ETTp in both normal swallowers and in patients with complaints. This is important for two reasons. First, if we are performing fluoroscopic swallowing studies to identify pathology, we want the study to be as discriminating as possible between normal and abnormal function and to optimize information that we gain from a study that is time‐ and labor‐intensive and involves ionizing radiation. Choosing the round pill (Figures 2 and 3) is more likely to identify an area of hold‐up in those with swallow issues, even if these are subtle, compared to an oval pill shape. Second, when we consider advice to our patients (complaining of pill swallowing difficulties), we may suggest the patient change medication shape or formulation to an oval‐shaped pill (Figure 4) to assist in pill transit.

FIGURE 2.

Still image obtained from videofluoroscopic swallowing study showing the 13‐mm round barium pill in the proximal esophagus. A calibrating marker is seen at the mandible.

FIGURE 3.

Still image obtained from videofluoroscopic swallowing study showing the 13‐mm round barium pill in the distal esophagus.

FIGURE 4.

Still image obtained from videofluoroscopic swallowing study showing the oval pill in the esophagus. A calibrating marker is seen at the mandible.

The etiology of swallow dysfunction is diverse but often broadly grouped into structural pathology or motility issues, and further segregated according to site (oral, pharyngeal, and/or esophageal) [6, 9]. Miles et al. previously reported that two thirds of patients referred with pharyngeal symptoms for a VFSS have esophageal abnormalities with or without concurrent oropharyngeal dysfunction [5]. This is in part due to the overlapping sensory innervation in the aerodigestive tract making patients perceived location of bolus hold‐up unreliable [10, 11], and in part due to the well‐established interconnectivity of the aerodigestive tract meaning that many etiologies present with both pharyngeal and esophageal difficulties either concurrently, for example, Parkinson's disease [12] or as a secondary sequelae, for example, reflux irritation [13, 14]. Esophageal screening is therefore an important addition to the VFSS protocol. Administering a pill during the VFSS and screening the esophagus as part of the protocol increases the sensitivity of identifying esophageal abnormalities [4]. Commercially available 13‐mm diameter round pills enable identification of luminal narrowing smaller than the diameter of the given pill, such as a stricture, ring, or stenosis. Site and duration of pill stasis may help direct further investigations.

Interestingly, the round pill ETTp duration in healthy swallowers was significantly shorter than in patients (26 vs. 45 s) presenting to clinics with swallow complaints, indicating that patients may appreciate early physiological changes to their swallow, and that the round pill was discriminatory between normal and affected swallows. This supports using the 13 mm round pill in diagnostic studies to challenge the individual as far as possible and to improve detection of swallowing changes. The presenting diagnoses of the patients swallowing both pill types are well recognized to be associated with swallow impairment [3]. We therefore expected the results in this patient cohort to differ from healthy adults, as was the case. It is helpful to see that within a single patient there is still a difference in ETTp dependent on pill shape. This effectively provides an internal control to allow direct comparison of pill shapes, given that the round and oval pill swallows occurred within minutes of each other, thus under the same conditions. The oval gel‐capsule ETTp of normal swallowers did not differ from oval gel‐capsules ETTp in patients (5.4 vs. 9 s), suggesting that altering the shape of the pill can nullify pill‐dysphagia to some extent, and supporting advice to patients to consider shape when choosing pills that they swallow, for example, over the counter preparations and prescribed medications.

In this exploratory study of pill transit times, we have compared two pill formulations; however, there are many more permutations and additional factors that may affect pill performance. These include pill coating, the vehicle that the pill is swallowed with, pre‐lubrication of the pharynx, and the weight of the pill. In this study, all dummy medications were given with water, and further work is needed to examine differences in pill transit and stasis using other vehicles for assisting pill swallowing. VFSS assessment of different vehicles during pill swallowing would be helpful to delineate any changes. Gallo et al. demonstrated that inclined positioning (at least 45°) and moderate volume of water (> 60 mL) produced the greatest success in the passage of a 12.5 mm barium tablet through the esophagus in 20 healthy volunteers (70%–81% successful passage with 60 or 100 mL of water in inclined position) [15]. Hummler and colleagues compared “swallowability” as rated by participants in two cohorts of adults (younger 19–36 years and older 65–94 years) given dummy medication in differing weights and shapes (oval, round, oblong) [16]. There was no objective identification of the pills. They reported that > 80% of older adults only viewed swallowing the 250 mg oval tablet as “well swallowable” compared to younger participants who rated both the 250 and 500 mg oval tablets as “well swallowable.” This study is hampered by a lack of objective visualization of the actual pills or any quantification of esophageal transit times [16].

Similarly, manufacturers can apply pill coatings to streamline pill transit, alter taste or absorption/release properties, stabilize contents, or protect against gastric enzymes [17]. Coatings may be sugars, for example, methylcellulose or polyvinyl acetate phthalate (PVAP) (leading to significant increase in pill weight and size, e.g., 30%–50% increase), or films, for example, polymers like hydroxypropyl methyl cellulose (HPMC) or plasticizers such as polyethylene glycol (PEG) [17]. Film coating is usually preferred as it is only a thin layer, resulting in a minimal weight increase to the pill and may allow more active compound to be utilized. Further coatings include enteric coating with acrylates such as Eudragit that allow dissolution only at a certain pH (e.g., pH > 6 to avoid acidic gastric disintegration and allow migration to the bowel before dissolving) or effervescent dissolvable tablets with an acid and carbonate salt present to produce bubbles on water contact [17]. Pills in our study were either plain pressed powder uncoated round 13 mm barium sulfate pills or 13‐mm long, hand‐filled gelatine capsules. Although we wondered if the gel‐capsules used in this study could become adherent to the aerodigestive tract mucosa when wet, we still found the gel‐capsules transited fastest through the esophagus in both healthy and symptomatic adults. All participants were given the same volume of water to swallow each pill, and all were positioned upright throughout the VFSS assessment.

Age differed significantly across groups. Age has previously been shown to affect ETT for a 20‐mL bolus, but the age effect has not been noted in pill swallowing [6]. There is relevance, though, from a holistic point of view in considering age in relation to medication swallowing, as older individuals are more likely to need to take greater numbers of medications. Gender was also asymmetric across cohorts but has not previously been associated with pill swallowing issues. The imbalanced age between groups likely reflects small subgroup sizes in this study.

More than 50% of dual pill swallowers presented with gastrointestinal symptoms (esophageal dysmotility, cricopharyngeal dysfunction) and 34% had undergone treatment for head and neck cancer, typically with surgery followed by adjuvant radiotherapy. These treatments can lead to significant swallow morbidity and xerostomia, impacting pill and solid food transit (Table 1). Our previous large cohort study (n = 756) also found significant differences in ETT in patients with neurological conditions compared to healthy controls or those with respiratory conditions [3]. These aetiologies, with known risks of esophageal dysfunction, may explain the disparity in ETTp between normal swallowers and patients for a single pill type, for example, round pill normal swallow mean ETTp 26 s versus 45 s for the patient cohort.

5. Limitations

Mean age of the patient group was significantly greater than healthy volunteers, and this coincides with the patient round pill ETTp also being significantly longer than volunteers. This may reflect age impacting esophageal function. However, our comparison of round versus oval tablets swallowed by the same patient demonstrated significant differences in ETTp related to pill shape, despite this group having the greatest mean age (69 years). Healthy volunteers only took one of the two pill types (round or oval) to meet ethical requirements. A greater sample size of healthy adults undertaking swallowing incorporating swallows of both pill types and other different formulations would provide more insight into pill swallowability. As discussed above, other pill parameters that may have affected transit time besides shape were not assessed in this study. Only one group of patients was studied—those presenting to an outpatient SLT clinic with complaints of solid food and pill swallowing issues. These were ambulant patients, and pill transit may be different in other pathologies or across a larger sample size.

6. Conclusions

The shape of a pill influences the esophageal transit time, with oval pill shapes demonstrating significantly shorter overall ETTp than round pills. This should be considered (a) when performing a diagnostic VFSS that is designed to challenge the individual, when a round pill is likely most appropriate, and (b) when counseling patients with swallow disorders about pill swallowing, when an oval shape may be easier for a patient to manage. Further work is needed to test additional pill parameters and their effects on transit times.

Conflicts of Interest

The authors declare no conflicts of interest.

Allen J., MacKay G., and Miles A., “Pill Shape Determines Esophageal Transit Times—A Pill‐to‐Pill Study,” The Laryngoscope 135, no. 10 (2025): 3588–3593, 10.1002/lary.32266.