Use of the 13C-octanoic acid breath test for assessment of solid-phase gastric emptying in dogs

Usefulness of the Beagle Model in the Evaluation of Paracetamol and Ibuprofen Exposure after Oral Administration to Pediatric Populations: An Exploratory Study

The present study aimed to explore the usefulness of beagle dogs in combination with physiologically based pharmacokinetic (PBPK) modeling in the evaluation of drug exposure after oral administration to pediatric populations at an early stage of pharmaceutical product development. An exploratory, single-dose, crossover bioavailability study in six beagles was performed. A paracetamol suspension and an ibuprofen suspension were coadministered in the fasted-state conditions, under reference-meal fed-state conditions, and under infant-formula fed-state conditions. PBPK models developed with GastroPlus v9.7 were used to inform the extrapolation of beagle data to human infants and children. Beagle-based simulation outcomes were compared with published human-adult-based simulations. For paracetamol, fasted-state conditions and reference-meal fed-state conditions in beagles appeared to provide adequate information for the applied scaling approach. Fasted-state and/or reference-meal fed-state conditions in beagles appeared suitable to simulate the performance of ibuprofen suspension in pediatric populations. Contrary to human-adult-based translations, extrapolations based on beagle data collected under infant-formula fed-state conditions appeared less useful for informing simulations of plasma levels in pediatric populations. Beagle data collected under fasted and/or reference-meal fed-state conditions appeared to be useful in the investigation of pediatric product performance of the two investigated highly permeable and highly soluble drugs in the upper small intestine. The suitability of the beagle as a preclinical model to understand pediatric drug product performance under different dosing conditions deserves further evaluation with a broader spectrum of drugs and drug products and comparisons with pediatric in vivo data.

Effects of the neurokinin-1 antagonist maropitant on canine gastric emptying assessed by radioscintigraphy and breath test

Objective: Delayed gastric emptying is a well-recognised phenomenon in a number of canine disease conditions. Only a limited number of drugs have been reported to have some gastrokinetic effect in the dog. The aim of this study was to investigate prokinetic effects of maropitant. Material and methods: In a cross-over study 24 healthy adult Beagle dogs were randomised to receive either maropitant (2 mg/kg q24 h PO), cisapride (1 mg/kg q12 h PO) or placebo (vitamin- B12, 10 μg/dog q24 h PO) for 7 days with a 7-day washout period between treatments. Gastric emptying was measured simultaneously via 99mTechnetium radioscintigraphy and 13C-sodium acetate breath testing for 6 hours post-feeding. The decrease in radioactive counts in the stomach and the increase in 13CO2 concentration in exhaled breath (measured via gas chromatography) were plotted against time. The area under the curve was determined for each test and the time to 25%, 50% and 75% gastric emptying was calculated for each method. Friedman test was used to compare gastric emptying times. Results: With both methods, no difference for gastric emptying times was observed for any treatment. Conclusion and clinical relevance: Neither maropitant nor cisapride were shown to have an effect on gastric emptying in healthy beagles using radioscintigraphy or breath test when compared to placebo. Consequently, neither drug can be recommended as a gastric prokinetic in dogs.

Validation of Ultrasonography for Assessment of Gastric Emptying Time in Healthy Cats by Radionuclide Scintigraphy

Background

The prevalence of gastric emptying (GE) disorders in cats is unknown due to lack of clinically applicable diagnostic tests.

Objectives

The principal aim of this study was to assess correlation between scintigraphic and ultrasonographic measurements of GE time (GET) in healthy cats. Additionally, variability of ultrasonographic GET, and correlation between scintigraphy and ultrasonographic parameters of gastric motility were evaluated.

Animals

Eight healthy domestic shorthair cats.

Methods

Prospective study. Scintigraphic GET was determined using a solid test meal containing 4 mCi ^99mTc‐mebrofenin. Each cat had 3 separate ultrasonographic assessments of GE, performed independent of scintigraphic assessment, after solid test meal consumption. The motility index (MI) of antral contractions was plotted against time and time for each fraction of the area under the MI curve determined. Ultrasonographic GET and MI were correlated to scintigraphic GET.

Results

Scintigraphic GET (mean ± SD) for 25, 50, and 75% GE was 103 ± 32 minutes, 196 ± 45 minutes, and 288 ± 62 minutes, whereas sonographic GET for 25, 50, and 75% GE was 106 ± 13 minutes, 203 ± 19 minutes, and 305 ± 27 minutes. There was good correlation between scintigraphic and sonographic GET (r = 0.72–0.82) at 45–90% fractional GE and between scintigraphic GET and time of corresponding MI curve fraction (r = 0.78–0.86) at 40–90% fraction of the MI curve. There was moderate intraindividual variability for sonographic GET and MI curve fraction times as well as significant variation among individuals.

Conclusions and clinical importance

Ultrasonography is a valid alternative to scintigraphy for assessment of solid‐phase GE and allows assessment of postprandial gastric motility in healthy cats.

Assessment of the variation associated with repeated measurement of gastrointestinal transit times and assessment of the effect of oral ranitidine on gastrointestinal transit times using a wireless motility capsule system in dogs

This study aimed to evaluate the variation associated with repeated measurement of gastrointestinal (GI) transit times and the effect of oral ranitidine on GI transit times in healthy dogs using a wireless motility capsule (WMC) system. Eight privately owned healthy adult dogs were enrolled, and one developed diarrhea and was removed from the study. For the first 3 repetitions, each dog was fed a standard meal followed by oral administration of a WMC. For the 4th repetition, each dog was given ranitidine hydrochloride (75 mg PO every 12 hours) prior to and during assessment of GI transit times. Mean between-subject coefficients of variation for gastric emptying time (GET), small and large bowel transit time (SLBTT), and total transit time (TTT) were 26.9%, 32.3%, and 19.6%, respectively. Mean within-subject coefficients of variation for GET, SLBTT, and TTT were 9.3%, 19.6%, and 15.9%, respectively. Median GET, SLBTT, and TTT without ranitidine were 719, 1,636, and 2,735 minutes, respectively. Median GET, SLBTT, and TTT with ranitidine were 757, 1,227, and 2,083 minutes, respectively. No significant differences in GI transit times were found between any of the 4 repetitions. Under these experimental conditions, no significant effects of oral ranitidine on GI transit times were observed.

Effect of mosapride on prednisolone-induced gastric mucosal injury and gastric-emptying disorder in dog

Previous report demonstrated that prokinetic agent mosapride has anti-ulcerogenic action in rat-indomethacin gastric mucosal injury model. Here, we assessed the prophylactic effect of mosapride on gastric mucosal injury and emptying disorder induced by prednisolone in dogs. Crossover study design was employed. Six healthy beagles were administered prednisolone alone (2 mg/kg, twice a day [BID] subcutaneously) and prednisolone with mosapride (1 mg/kg, BID, orally), followed by an interval of at least 6 weeks. In each treatment, gastric mucosal injury was scored endoscopically according to the modified Lanza scale, and gastric emptying was assessed with (13)C-octanoic acid breath test. The incidence of gastrointestinal adverse events was also investigated. Coadministration of mosapride with prednisolone significantly (P<0.05) reduced the gastric mucosal injury score (mean ± SD, 17.67 ± 6.96), compared with that of prednisolone treatment alone (25.50 ± 13.03). Prednisolone treatment delayed the half-emptying time (184 ± 45 min) compared with that of controls (137 ± 19 min), and coadministration of mosapride improved this gastric-emptying delay (143 ± 29 min). Furthermore, the incidence of the gastrointestinal adverse event vomiting became less frequent upon coadministration with mosapride. In addition to its prokinetic action, our study suggests that mosapride has an anti-ulcerogenic action in dogs. The use of mosapride in combination with prednisolone is effective for attenuating prednisolone-induced gastrointestinal adverse events.

Real-time ultrasonographic evaluation of canine gastric motility in the postprandial state

Gastric motility is affected by several pathological conditions which may induce upper gastrointestinal clinical symptoms. The pathogenesis of canine gastric motility disorders is poorly understood because of methodological limitations. This study aimed at establishing a simple method for evaluating postprandial gastric motility in dogs. Gastric motility was ultrasonographically assessed in 7 healthy beagles using a technique previously described in humans. The motility index (MI), an indicator of gastric antral motility, was calculated by measuring the area of the gastric antrum in both a contracted and relaxed phase and by counting the number of contractions. The MI was measured every 30 min for 3 hr after feeding and compared with gastric emptying as assessed by a (13)C-octanoic acid breath test. The MI at 30 min had the lowest variability in the 7 dogs (mean SD, 9.77 ± 0.42; coefficient of variance, 4.25%), and a significant correlation was observed with gastric emptying coefficient (R(2)=0.8126, P=0.005) and half-emptying time (R(2)=0.654, P=0.027). When atropine was administered, a significant decrease in the MI at 30 min was observed compared with the control (9.77 ± 0.42 vs. 5.19 ± 0.22, P=0.0003). In conclusion, evaluation of the MI at 30 min is suitable for assessing gastric motility and enables us to assess gastric motility simply in a short time. By using this method, further studies for the pathogenesis of canine gastric motility disorders are warranted.

Variability associated with repeated measurements of gastrointestinal tract motility in dogs obtained by use of a wireless motility capsule system and scintigraphy

OBJECTIVE

To compare repeatability of measurements of gastrointestinal tract motility in healthy dogs obtained by use of a wireless motility capsule (WMC) and scintigraphy.

ANIMALS

6 healthy adult dogs (mean +/- SD body weight, 21.5 +/- 1.8 kg).

PROCEDURES

A radiolabeled test meal was offered immediately after oral administration of a WMC. Serial static scintigraphic abdominal images were acquired for 270 minutes. A dedicated remote receiver was used for data collection from the WMC until the WMC was expelled in the feces. Each dog was evaluated 3 times at intervals of 1 to 2 weeks.

RESULTS

Mean gastric emptying half-time measured by use of scintigraphy (T(1/2)-GES) for each dog ranged from 99.9 to 181.2 minutes. Mean gastric emptying time (GET) measured by use of the WMC (GET-WMC) in each dog ranged from 385.3 to 669.7 minutes. Mean coefficient of variation was 11.8% for T(1/2)-GES and 7.8% for GET-WMC. The intraclass correlation coefficient was 69% for T(1/2)-GES and 71% for GET-WMC. Results for a nested analysis of covariance suggested that both methods were comparable for the evaluation of gastric emptying.

CONCLUSIONS AND CLINICAL RELEVANCE

Scintigraphy and a WMC system had similar variation for assessment of gastric emptying. Moderate intraindividual variability was detected for both methods and must be considered when interpreting test results for individual dogs. Repeatability of measurements obtained by use of the WMC was equivalent to that obtained by use of scintigraphy. The WMC system offers a nonradioactive, user-friendly method for assessment of gastric emptying in dogs.

Factors influencing the gastric residence of dosage forms in dogs

An appreciation of the variables influencing canine gastric transit time is of interest both because of the push to develop pharmaceutical products that meet the therapeutic needs of the veterinary patient and because of efforts to improve our understanding of the strengths and weaknesses associated with the use of the dog as a preclinical model to support human product development. The gastric transit time of monogastric species is influenced by many factors. Physiological variables include the time of dosing relative to the phase of the interdigestive migrating myoelectric current (IMMC), the sieving properties of the pylorus, the presence or absence of food, and the inherent crushing force of the stomach. Pharmacological factors include particle size, shape and density, drug solubility, and the hardness of the tablet. Despite the importance of understanding the factors influencing gastric residence time in dogs, an in-depth examination of currently available information on this topic has not as yet been published. Therefore, this review provides an examination of each of these factors and their potential impact on canine oral drug absorption characteristics.

Retention of acetaminophen in an in vitro model of solid-phase gastric emptying of animals

OBJECTIVE

To apply an in vitro model for assessment of the solid-phase binding capacity of acetaminophen and thus assess the reliability of this marker for evaluation of solid-phase gastric emptying in vivo in animals.

SAMPLE POPULATION

4 test meals.

PROCEDURES

A spectrophotometric method for detection of acetaminophen was validated and applied for assessment of the percentage retention of acetaminophen in the solid phase of 4 test meals. The gastric milieu was simulated by incubating each meal in artificial gastric juice for 2 hours in a shaking water bath maintained at 37 degrees C. Solid-phase retention was then assessed 3 times by measuring the amount of acetaminophen that had leached into the liquid phase.

RESULTS

Acetaminophen was poorly retained in the solid phase of all the test meals examined in the study. There was also a large degree of variability in the percentage retention for each meal when the experiment was repeated 3 times.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of the results of this in vitro study confirmed that acetaminophen may not be an appropriate marker of solid-phase gastric emptying. The acetaminophen gastric emptying test should be applied only for the assessment of liquid-phase emptying in animals.

Comparison of accuracy and precision of heart rate calibration methods to estimate total carbon dioxide production during 13C-breath tests

BACKGROUND

13C-breath tests are noninvasive tools to measure gastrointestinal function and nutritional interventions. Calculation of percentage dose recovered of 13C in exhaled breath requires knowledge of CO2 production rate (VC02). A resting value is usually assumed, but this can underestimate VC02 because subjects are unlikely to remain at rest during tests that last for many hours. There is a need for a method to estimate nonresting VC02 during 13C-breath tests.

OBJECTIVE

To calibrate a heart rate monitor to continually estimate VC02 during 13C-breath tests.

DESIGN

Proof of concept study.

SUBJECTS

Eight healthy adults, 10 healthy children and six children with cystic fibrosis.

METHODS

Heart rate and VC02 were measured simultaneously at resting and nonresting levels. A new calibration method (smoothing heart rate and fitting a sigmoid function) was compared with published methods. A [ 3C]acetate breath test was used to demonstrate the range of physical activity during breath tests.

RESULTS

The new calibration method was more accurate than existing methods (mean bias -0.0002%, 95% confidence interval (CI) -0.0007, 0.0003% of the mean measured VC02). Smoothing heart rate gave a more precise estimate of VC02 and a more accurate estimate of resting energy expenditure (mean bias -0.09, 95% Cl -0.22, 0.05 mmol CO2 min-' m-2 body surface area) than using raw data (mean bias -0.21, 95% Cl -0.38, -0.04 mmol CO2 min' m-2 body surface area). Physical activity level ranged from 1.0 to 2.5 in children, and 1.0 to 1.5 in adults.

CONCLUSION

Use of smoothed HR with a sigmoid function provides an accurate method of estimating nonresting VC02 during 13C-breath tests.

Comparison of the carbon 13-labeled octanoic acid breath test and ultrasonography for assessment of gastric emptying of a semisolid meal in dogs

OBJECTIVE

To compare the rate of gastric emptying of a semisolid meal by use of the carbon 13-labeled octanoic acid breath test (13C-OBT) and gastric emptying ultrasonography (GEU) in dogs.

ANIMALS

10 healthy dogs.

PROCEDURE

Food was withheld from dogs for 12 hours before ingestion of a test meal (bread, egg, and skimmed milk) containing 13C-octanoic acid. The gastric antrum was visualized by use of a 6.5-MHz microconvex transducer, and the area of the ellipse defined by the craniocaudal and ventrodorsal diameters of the stomach was measured. Samples of expired air and antral images were obtained 30 minutes before ingestion of the test meal and then every 15 minutes for 4 hours and every 30 minutes for a further 2 hours. The half-dose recovery time with the 13C-OBT (t1/2[BT]) and the gastric half emtying time with GEU (t50%[GEU]) was calculated.

RESULTS

Mean +/- SD values for the t1/2(BT) and t50%(GEU) were 3.44 +/- 0.48 hours and 1.89 +/- 0.78 hours, respectively. A significant correlation was detected between the t1/2(BT) and t50%(GEU), although there was a large (1.55 hours) mean difference between these indices.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that there was a correlation between the rate of solid-phase gastric emptying assessed by use of GEU and the 13C-OBT in dogs. Gastric emptying ultrasonography may be a useful, noninvasive method for assessment of the rate of solid-phase gastric emptying in dogs.

Use of 13C-Acetate Breath Test for Assessment of Gastric Emptying in Horses

This study aimed to establish and standardize a breath test that uses 13C-acetate in a liquid diet for evaluation of gastric emptying in horses. Seven adult healthy thoroughbreds were used in this study. They were given 13C-acetate (125 mg, 250 mg, or 500 mg) in a test meal (2000 ml liquid diet) via an intranasal catheter. 13C concentrations in the exhaled CO2 were measured in samples taken before and after test meal administration using an infrared absorption spectroscope. In the 500 mg 13C-acetate group, Delta13CO2 showed a steep gradient immediately after meal administration compared to the 125 mg and 250 mg groups. Therefore, t(max) in the 500 mg group was easier to determine than in the 125 mg and 250 mg groups. In the 500 mg group, GEC, half-empty time (t1/2), calculated t(max) (t(lag)), and t(max) were 1.95 +/- 0.28 (mean +/- SD), 229.2 +/- 57.0 (min), 139.2 +/- 22.2 (min), and 124.0 +/- 28.4, respectively. Differences in CV observed in the 500 mg group were lower than those in the 125 mg and 250 mg groups. This study demonstrates that the 13C-acetate breath test is useful for evaluating gastric emptying in horses since it is non-invasive and does not require set up of special facilities or equipment. Optimum evaluation of gastric emptying in horses can be achieved with 500 mg of 13C-acetate given in a liquid diet.

Simple and Noninvasive Breath Test Using 13C-Acetic Acid to Evaluate Gastric Emptying in Conscious Rats and Its Validation by Metoclopramide

The (13)C-breath test has been used to clinically evaluate gastric emptying. However, this method has not been sufficiently validated in experimental animals. The present study aimed to establish a simple and noninvasive (13)C-breath-test system in Sprague-Dawley male rats. After fasting, rats were orally administered Racol containing (13)C-acetic acid and housed in a desiccator. The expired air in the chamber was collected in a breath-sampling bag using a tube and aspiration pump. The level of (13)CO2 in the expired air was measured using an infrared spectrometer at appropriate intervals for 120 min. During this period, the rate of (13)CO2 excretion increased, peaked, and decreased thereafter. The maximum concentration (Cmax) and area under the curve (AUC120 min) of (13)CO2 excretion increased in volume- and dose-dependent manners. The time taken to reach the maximum concentration (Tmax) of (13)CO2 excretion increased as the volume increased, but was not affected by the dose of (13)C-labeled acetic acid. Metoclopramide dose-dependently increased the Cmax and shortened Tmax of (13)CO2 excretion compared with those of the control rats, whereas the AUC120 min was not affected. These results confirm that this simple method can successfully evaluate gastric emptying. Moreover, this system is suitable for investigating additional physiological functions using other labeled compounds.

Effect of body size on gastric emptying using the 13C-octanoic acid breath test

The 13C-octanoic acid breath test (OABT) may be a useful non-invasive method for assessing the rate of gastric emptying in dogs. The aim of this study was to determine whether an association exists between body size and rate of gastric emptying in dogs. Fifty-five dogs ranging from 6 to 39 kg were recruited and rate of gastric emptying was assessed using the OABT. The time to peak 13CO2 excretion (tmax) and half-dose recovery time (t1/2) were calculated. The OABT was simple to perform and well tolerated by the dogs. Mean (sd) tmax was 2.67 hours (0.6) and mean t1/2 was 3.38 hours (0.79). Inter-individual variation in the rate of gastric emptying was 23.3 per cent for t1/2 and 22.5 per cent for tmax. No association was detected between the rate of gastric emptying and body surface area, mass, age, sex or test operator. The OABT may be a useful non-invasive and non-radioactive test for assessment of the rate of gastric emptying in dogs in clinical practice.

Current and future uses of breath analysis as a diagnostic tool

The analysis of exhaled breath is a potentially useful method for application in veterinary diagnostics. Breath samples can be easily collected from animals by means of a face mask or collection chamber with minimal disturbance to the animal. After the administration of a 13C-labelled compound the recovery of 13C in breath can be used to investigate gastrointestinal and digestive functions. Exhaled hydrogen can be used to assess orocaecal transit time and malabsorption, and exhaled nitric oxide, carbon monoxide and pentane can be used to assess oxidative stress and inflammation. The analysis of compounds dissolved in the aqueous phase of breath (the exhaled breath condensate) can be used to assess airway inflammation. This review summarises the current status of breath analysis in veterinary medicine, and analyses its potential for assessing animal health and disease.

Laboratory assessment of gastrointestinal function

Over the past decade, several laboratory tests have been introduced to veterinary medicine that allow the minimally invasive assessment of diseases of the gastrointestinal tract, liver, and pancreas. Although some of those tests have limited clinical use in a practice setting and have more use as research tools, other tests, such as serum cobalamin and folate concentrations, find wide application in everyday veterinary practice. In some cases, definitive diagnosis requires invasive or expensive procedures, but these new laboratory tests have greatly aided veterinarians in diagnosing gastrointestinal diseases. This discussion provides an overview of new diagnostic tests that will allow the minimally invasive assessment of gastrointestinal function.

A review of methods for assessment of the rate of gastric emptying in the dog and cat: 1898-2002

Gastric emptying is the process by which food is delivered to the small intestine at a rate and in a form that optimizes intestinal absorption of nutrients. The rate of gastric emptying is subject to alteration by physiological, pharmacological, and pathological conditions. Gastric emptying of solids is of greater clinical significance because disordered gastric emptying rarely is detectable in the liquid phase. Imaging techniques have the disadvantage of requiring restraint of the animal and access to expensive equipment. Radiographic methods require administration of test meals that are not similar to food. Scintigraphy is the gold standard method for assessment of gastric emptying but requires administration of a radioisotope. Magnetic resonance imaging has not yet been applied for assessment of gastric emptying in small animals. Ultrasonography is a potentially useful, but subjective, method for assessment of gastric emptying in dogs. Gastric tracer methods require insertion of gastric or intestinal cannulae and are rarely applied outside of the research laboratory. The paracetamol absorption test has been applied for assessment of liquid phase gastric emptying in the dog, but requires IV cannulation. The gastric emptying breath test is a noninvasive method for assessment of gastric emptying that has been applied in dogs and cats. This method can be carried out away from the veterinary hospital, but the effects of physiological and pathological abnormalities on the test are not known. Advances in technology will facilitate the development of reliable methods for assessment of gastric emptying in small animals.

A comparison of the rate of recovery of 13CO2 in exhaled breath with 2H in body water following ingestion of [2H/13C]octanoic acid in a dog

The objective of this study was to assess post-gastric processing of octanoic acid (OA) by comparing the rate of recovery of 13C in breath with the rate of recovery of 2H in saliva following ingestion of [2H/13C]OA. A test meal with 100mg [13C]OA and 750 mg [2H]OA was ingested on two separate occasions by one dog. Exhaled breath and saliva samples were collected at set time points for 6h following ingestion of the test meal. Two indices were computed, half recovery time (t(1/2)) and the time of peak excretion (t(max)). Recovery of 2H in saliva was quicker than recovery of 13C in breath as determined by the difference in the indices for each isotope; 1.33 and 1.59 h for t(1/2) and t(max), respectively. These findings suggest that the post-gastric processing of OA imposes a delay on the recovery of 13C in breath in the dog, as occurs in man and in the horse.