Journal of Feline Medicine and Surgery (2010) 12, 286e290doi:10.1016/j.jfms.2009.09.017

A comparative study evaluating the esophageal transittime of eight healthy cats when pilled with the FlavoRxpill glide versus pill delivery treats

Alexander D Bennett BS1, Catriona M MacPhail DVM, PhD, Diplomate ACVS

1*,Debra S Gibbons DVM, MS, DACVR

2, Michael R Lappin DVM, PhD, Diplomate ACVIM1

1Department of Clinical Sciences,Colorado State University, FortCollins, Colorado State University,USA2Environmental and RadiologicalHealth Sciences, Colorado StateUniversity, Fort Collins, ColoradoState University, USA

*Corresponding author. Tel: þ1-970-2211275. E-mail: cmacphai@lamar.colostate

1098-612X/09/040286+05 $36.00/0

Retention of tablets or capsules in the feline esophagus can be associated withesophagitis and esophageal stricture formation. The objective of this study wasto evaluate the esophageal passage of tablets and capsules when administeredwith either a one-step pill gun with flavored liquid (FlavoRx pill glide) or a pilldelivery treat (Pill Pockets). Four different medication administrations wereevaluated on different days in eight normal cats: tablets with FlavoRx pill glide(T-FG), tablets with pill delivery treats (T-PP), capsules with FlavoRx pill glide(C-FG) and capsules with pill delivery treats (C-PP). The estimated averagetransit time was 36 s for T-FG, 60 s for T-PP, 16 s for C-FG, and 24 s for C-PP. Theresults of this study suggest that either pill delivery method is acceptable forsuccessful passage of tablets or capsules into the stomach of cats using a singlereplicate.

Date accepted: 29 September 2009 � 2009 ISFM and AAFP. Published by Elsevier Ltd. All rights reserved.

Administration of oral medications is a neces-sary component of feline practice. Often tab-lets and capsules are simply forced to the

back of the cat’s oral cavity with the hope that it isswallowed without the veterinarian, veterinary tech-nician, or owner being bitten or scratched. In this sce-nario there is increased risk of exposure to infectiousagents, such as Bartonella henselae, the primary causeof cat scratch disease in people.1 The stress inducedupon the cat is only heightened when multiple at-tempts are needed, further increasing the occurrenceof bite wounds and exposure to pathogens. Further-more, dry pilling cats can lead to esophageal retentionof the medications.2e4 For example, administration oftablets or capsules to cats without water has resultedin esophageal retention for 11 min in up to 50% ofcats.4 This can cause discomfort which makes the catless receptive on future attempts to administer medi-cations. In addition, if retention of irritating medica-tions is prolonged, esophagitis with or withoutstricture formation can result. This has been identifiedwith commonly used antibiotics, such as doxycyclineand clindamycin in cats.5,6

Numerous strategies have been used in an attemptto identify a reliable delivery system for feline

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� 2009 ISFM a

medications. Use of a device to deliver the tablet or cap-sule to the caudal pharynx (‘pill gun’) can lessen therisk of exposure to infectious agents as this avoidsplacement of fingers into the cat’s mouth, but doesnot address the issue of esophageal retention. Adminis-tration of water after delivering the tablet or capsulehas been effective in shortening the transit time to thestomach, but requires additional handling of the cat.2

Coating the tablet or capsule with butter or other vis-cous material like a dietary supplement (Nutrical, Vet-quinol Pharmaceuticals, Buena, New Jersey) has alsobeen shown to lessen the risk of esophageal retention.4

Pill delivery treats are available that cover the tablet orcapsule, mask the taste of the medication, and promoteingestion by the cat (Greenies Pill Pockets, S&M NuTec,Kansas City, Missouri; Fig 1B). To our knowledge, it hasnot been demonstrated that medication administrationin pill delivery treats results in normal esophageal tran-sit. Many drugs supplied as tablets or capsules can beliquefied. However, this requires additional time andexpense, and stability has not been determined for alldrugs. Transdermal application of drugs is another po-tential method for medication delivery. This modalityhas been studied to a limited degree in cats and it wasfound that the bioavailability of drugs mixed with pleu-ronic lecithin organogel for transdermal administrationcan be highly variable between cats.7,8 Thus, improvedoral drug delivery systems are still needed.

nd AAFP. Published by Elsevier Ltd. All rights reserved.

Fig 1. Medication delivery methods evaluated in thisstudy. (A): FlavoRx pill glide (FlavoRx, Columbia, MD);(B): Greenies Pill Pockets (S&M NuTec, Kansas City, MO).

287comparative study evaluating the esophageal transit time

The FlavoRx pill glide (FlavoRx, Columbia, Mary-land; Fig 1A) is a device designed to deliver a bolusof flavored liquid following tablet or capsule releaseinto the animal’s mouth in one step. This is proposedto facilitate tablet or capsule delivery to the stomach,which may prevent esophagitis and stricture forma-tion. The purpose of this study was to determine theesophageal transit time for barium tablets and cap-sules when administered by use of this device andwithin pill delivery treats.

Materials and methods

Cats

Eight clinically normal, mixed sex, neutered, youngadult (approximately 1 year) research cats were en-rolled in this study. The cats were determined to behealthy on physical examination and had normalvalues on serum biochemistry profile, and completeblood cell count. This study was approved by the An-imal Care and Use Committee of Colorado State

University and the cats were adopted into privatehomes or entered into other studies at the end ofthis project.

Acclimation period

Two weeks prior to initiating the study, time wasspent to acclimatize the cats to a specially designedPlexiglas box. This box is 41�15.5� 28 cm and waslarge enough to allow the cats to change positionwithin the box. Each cat spent 5 min in the Plexiglasbox every other day and was free fed Greenies PillPockets while within the box. This made their timein the box a positive experience and they became ac-customed to the treats at the same time. On the alter-nate days, each cat was allowed to taste the fluid usedwith the FlavoRx pill glide system. We inferred thatthe fluid was palatable based on the positive responsefrom the cats. The cats were not pilled or forciblymade to taste either delivery method during this time.

Tablets and capsules

Inert barium sulfate tablets (E-Z Disk, E-Z-EM, LakeSuccess, New York), 0.5 inches in diameter, were cutand shaped into 4 mm� 2 mm tablets. This tablet sizeapproximates the typical size of many medicationsused in cats, including standard dosage of doxycycline(1⁄4 of 100 mg tablet) and a 50 mg amoxicillin tablet. Bariumsulfate was also used to fill #4 gel capsules. These sizesof tablets and capsules were also used in a previousstudies evaluating feline esophageal transit times.2,3

Test periods

Barium tablet and capsule transit was determined byfluoroscopy. On the first day of the study, each catwas placed into the Plexiglas box and a tablet ina Greenies Pill Pockets (group T-PP) was then fed tothe cat. Fluoroscopy was started immediately andwas used to evaluate tablet passage through theesophagus continuously from 0 to 30 s, and then atthe 60, 90, 120, 180, 240, 300, and 360 s after adminis-tration. Exact transit time was recorded if it was lessthan 30 s. Otherwise, transit time was estimated tobe the individual time point when the tablet or cap-sule was found to be in the stomach. Fluoroscopicevaluation was discontinued as soon as the tabletwas visualized within the stomach. Any cat with a re-tained tablet at 360 s was to be administered a 10 mlbolus of water to facilitate transit of the tablet intothe stomach. The same protocol was repeated thenext day using barium sulfate tablets administeredwith the FlavoRx pill glide (group T-FG). The studywas repeated the following week with an identicalprotocol using the #4 gel capsules instead of tablets.On the first day, the cats were fed the capsules inGreenies Pill Pockets (group C-PP) and on next daythe capsules were administered using the FlavoRxpill glide (group C-FG).

288 AD Bennett et al

Statistical evaluation

The number of tablets and capsules successfully pass-ing at each time interval was expressed as the propor-tion of successful passages per total number ofattempts per time interval and presented descrip-tively. Average transit times between methods for pillsor capsules were compared by Wilcoxon signed ranktest with significance defined as P< 0.05.

Results

Medication administration

All cats tolerated the box to an acceptable degree withminimal to no undue stress (Fig 2). However, all butone cat (capsule) refused to voluntarily ingest theGreenies Pill Pockets while in the Plexiglas box inthe fluoroscopy room. Thus, the medication wasplaced into the caudal pharynx to begin the fluoros-copy. Administration of pills and C-FG was readily ac-cepted by all but two cats (group C-FG). In these twocats, the medication was accepted on the second ad-ministration performed several minutes later.

Esophageal transit times

Tablets and capsules passed into the stomach in all catswith both delivery methods in less than 300 s (Figs 3and 4). The percentage of successful passages into thestomach at 30 s was 62.5% for T-FG, 62.5% for T-PP,100% for C-FG and 75% for C-PP. The percentage of suc-cessful passage at 60 s was 87.5% for T-FG, 75% for T-PP,100% for C-FG, and 100% for C-PP. The percentage ofsuccessful passage at 90 s was 87.5% for T-PP, and100% for all other groups. The average transit timebased on the method of measurement previously de-scribed was 36 s for T-FG (range 15e60 s), 60 s forT-PP (range 16e240 s), 16 s for C-FG (range 7e30 s),

Fig 2. Image of a cat within the specially designed Plexi-glas box.

and 24 s for C-PP (range 14e60 s). There were no statis-tical differences between groups.

Transient retention of tablet passage (transit time>30 s) occurred in three T-PP cats and in four T-FGcats. Retention most commonly occurred at the levelof the thoracic inlet (three cats), followed by the heartbase (two cats). Retention occurred in the remainingcats at the level of the cervical esophagus and theproximal thoracic esophagus. Transient retentiononly occurred in one C-PP cat at the level of the tho-racic inlet (between 30 and 60 s). No C-FG cats hadtransient retention.

DiscussionThis study demonstrates that FlavoRx pill glide andGreenies Pill Pockets are effective methods for poten-tiating successful transit of tablets and capsules intothe stomach of feline patients. A sufficient bolus sizeis needed to stimulate the proximal esophagus duringphysiologic swallowing to initiate primary and sec-ondary peristalsis. It is believed that the swallowingof a tablet or capsule alone stimulates primary esoph-ageal peristalsis, but that the volume of medication isnot sufficient to stimulate secondary peristalticwaves.3 The FlavoRx pill glide and Greenies PillPockets both appeared to facilitate tablet or capsuleentry into the stomach, and therefore, likely stimu-lated primary and secondary peristalsis.

Normal esophageal transit time in cats is unknown,however, one study arbitrarily defined normal as<30 s, prolonged as >30 s but <240 s, and entrappedas >240 s.3 In the study described here, average transittime was 60 s or less for all groups, and all tablets andcapsules were successfully passed into the stomach by90 s except for one T-PP cat. To minimize radiation ex-posure, continuous fluoroscopy was performed foronly 30 s and then performed briefly at each timepoint. For transit time >30 s, successful transit was re-corded as the time point that identified the tablet orcapsule within the stomach. By the nature of the studydesign, this could have led to an overestimation of re-tention time. From the results and observations of thisstudy, the majority of the cats in all groups had nor-mal transit time using both methods of medication de-livery, with only one T-PP cat having prolongedtransit. While the average transit time did not vary be-tween methods for pills or capsules, it is possible thatstatistical differences would have been recognized iflarger numbers of cats were studied.

In this study, none of the cats had retention of a tab-let or capsule for >300 s when administered in a pilldelivery treat. The major advantage to Greenies PillPockets is that cats may consume them spontaneously,such that no restraint is required to administer medi-cation. However, even though the cats were accli-mated to the box and treats, all but one cat wasreluctant to spontaneously consume the treats whilein the Plexiglas box in the radiology room. However,once the treat was placed in the oropharynx, the treat

Tablet transit

0%

20%

40%

60%

80%

100%

24018012090603015Seconds

Percen

t o

f cats w

ith

su

ccessfu

l tran

sit

GF-TPP-T

Fig 3. Percentage of cats with the tablet in the stomach at the designated time. T/FG¼ tablet administered with the pillglide device; T/PP¼ tablet in Pill Pocket.

289comparative study evaluating the esophageal transit time

and capsule or tablet was readily swallowed. Thus,one disadvantage of this medication delivery methodis the failure of some cats to consume the treat.

Pill guns or pill-pushers allow for administration ofmedications to fractious, uncooperative, and anorexiccats, however, pill gun administration of tablets hasbeen shown to result in significant esophageal reten-tion.4 This led to the recommendation to administera fluid bolus after administering the capsule or tablet.2

The FlavoRx pill glide is a one-step system that simul-taneously delivers medication and a fluid bolus. This

Caps

0%

20%

40%

60%

80%

100%

603015S

Percen

t o

f cats w

ith

su

ccessfu

l tran

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GF-CPP-C

Fig 4. Percentage of cats with the capsule in the stomach at theglide device; C/PP¼ capsule in Pill Pocket.

device delivers a 3 ml fluid bolus, which is half thevolume previously recommended for a wet-swallowtechnique.2 In this study, both capsules and tabletssuccessfully passed into the stomach and so thissmaller volume appears to be appropriate to stimulatesecondary esophageal peristalsis.

The flavored liquid used with the FlavoRx pill glidesystem appeared to be palatable to the cats of thisstudy. It is possible that client-owned cats requiringchronic administration of tablets or capsules couldbe conditioned to receive medications with minimal

ule transit

24018012090econds

designated time. C/FG¼ capsule administered with the pill

290 AD Bennett et al

to no restraint due to the positive response to the fla-vored liquid. As with other pill delivery devices, theFlavoRx pill glide system provides a measure of safetyto the person administering the medication as a sy-ringe-like device is used to deliver the medicationinto the oropharynx.

A limitation of this study is that the cats were onlypilled once as opposed to multiple times with eachpilling modality for both tablets and capsules. Someclient-owned cats require multiple medications andso it is possible repeated treatments may show differ-ent results from those described herein. In addition,the order in which each cat received a particularmethod of pill administration was not randomized.This would be more problematic had the transit timesbeen assessed in sequential order on the same day.However, there was a minimum of a 24 h delay in be-tween assessment of delivery methods in order tolimit the effect of environmental stress or hypersaliva-tion on the results. The authors acknowledge that anoptimal study design would have been to have the de-livery method randomized. Also, in an effort to mini-mize any potential negative effect of the uniquerestraint within the Plexiglass box, the authors electedto provide an acclimatization period for the cats. Thecats were not pilled or forcibly made to taste either de-livery method during this time. It is possible that thefamiliarity of the cats with the box and deliverymethods may have confounded the results, but giventhat only one cat voluntarily ingested the Greenies PillPockets and no cat voluntarily took the FlavoRx liquidthe authors feel the effect of the acclimatization periodwas minimal.

In summary, in the study presented here FlavoRxpill glide and Greenies Pill Pockets and were shownto be effective pilling modalities in preventing esophagealretention of medications in cats.

AcknowledgementsThis study was supported by an unrestricted donationfrom FlavoRx to the Center for Companion AnimalStudies at Colorado State University (www.csuvets.colostate.edu/companion/index.htm). The authorsthank Dr Steven Radecki, a private statisticalconsultant in Fort Collins, Colorado, for statisticalreview.

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