Pharmacokinetics, absorption, and excretion of radiolabeled revexepride: a Phase I clinical trial using a microtracer and accelerator mass spectrometry-based approach

Purpose

Gastroesophageal reflux disease involves the reflux of gastric and/or duodenal content into the esophagus. Prokinetic therapies, such as the selective 5-hydroxytryptamine receptor 4 agonist revexepride, may aid gastric emptying. This Phase I study evaluated the pharmacokinetics and excretion pathways of [¹⁴C]revexepride in healthy individuals using a microtracer approach with accelerator mass spectrometry.

Participants and methods

Six healthy men received a single oral dose of 2 mg [¹⁴C]revexepride containing ~200 nCi of radioactivity; blood, urine, and fecal samples were collected over a 10-day period.

Results

Almost 100% of ¹⁴C was recovered: 38.2%±10.3% (mean ± standard deviation) was recovered in urine, and 57.3%±0.4% was recovered in feces. Blood cell uptake was low, based on the blood plasma total radioactivity ratio of 0.8. The mean revexepride renal clearance was 8.6 L/h, which was slightly higher than the typical glomerular filtration rate in healthy individuals. Time to reach maximal concentration was 1.75±1.17 hours (mean ± standard deviation). No safety signals were identified.

Conclusion

This study demonstrated that revexepride had rapid and moderate-to-good oral absorption. Excretion of radioactivity was completed with significant amounts in feces and urine. Renal clearance slightly exceeded the typical glomerular filtration rate, suggesting the involvement of active transportation in the renal tubules.

A Phase I Study to Investigate the Absorption, Pharmacokinetics, and Excretion of [(14)C]Prucalopride After a Single Oral Dose in Healthy Volunteers

PURPOSE

Chronic constipation is a prevalent gastrointestinal disorder globally. It is often treated with medications such as laxatives. Newer therapies to improve gastric motility include the selective 5-hydroxytryptamine receptor-4 agonist prucalopride, which is licensed for the treatment of chronic constipation in adults. The aim of this study was to investigate the pharmacokinetic properties and excretion of prucalopride in healthy individuals, using a microtracer approach with (14)C radioactivity detection using liquid scintillation counting and accelerator mass spectrometry.

METHODS

This was a single-period, open-label, nonrandomized absorption, metabolism, and excretion study of [(14)C]prucalopride. Participants were 6 healthy men aged 18 to 50 years. After screening, participants were administered a single dose of [(14)C]prucalopride succinate 2 mg (~200 nCi). Postadministration, urine, feces, and blood samples were collected over a 10-day period. Safety and adverse event data were also collected.

FINDINGS

Almost 100% of the administered dose of radioactivity was recovered, with a mean (SD) of 84.2% (8.88%) recovered in urine and 13.3% (1.73%) recovered in feces. The mean blood-to-plasma concentration ratio of 1.9 indicated uptake of prucalopride into blood cells. The renal clearance of prucalopride was 17.0 (2.5) L/h, which is higher than the glomerular filtration rate in healthy individuals, suggesting active renal transport of prucalopride. Prucalopride was well tolerated, with no serious adverse events reported.

IMPLICATIONS

Prucalopride was well absorbed and excreted mainly by the kidneys, including both passive and active transporter mechanisms. Quantitative recovery of the radioactive dose was achieved. Consistent with previous studies, prucalopride was generally well tolerated. ClinicalTrials.gov identifier: NCT01807000.

Evidence that famciclovir (BRL 42810) and its associated metabolites do not inhibit the 6 beta-hydroxylation of testosterone in human liver microsomes

Famciclovir is the diacetyl 6-deoxy analog of the active antiviral compound penciclovir with potential use in the treatment of infections caused by the herpes family of viruses. The major pathway of metabolism of famciclovir is deacetylation to BRL 42359 followed by oxidation to penciclovir. It is possible that famciclovir may be coadministered with cyclosporin A to combat viral infections induced by immunosuppression in organ transplant and bone marrow transplant patients. As a result, information is required on possible interactions between the cytochrome P-450 3A substrate cyclosporin A and famciclovir and its metabolites in humans. In order to probe cytochrome P-450 3A activity, testosterone 6 beta-hydroxylation in two human liver microsomal preparations was measured. Nicardipine and ketoconazole, two drugs with known inhibitory interactions with cyclosporin A, were used as positive controls. Profiles of 6 beta-hydroxytestosterone production showed no inhibition effected by famciclovir, penciclovir, or BRL 42359 when marked inhibition was observed in incubations containing nicardipine, nifedipine, or ketoconazole. Further incubations of [14C]BRL 42359 with human liver cytosol and microsomes indicated that BRL 42359 is oxidized to penciclovir in cytosol but not in microsomes and that this reaction was not dependent on the presence of NADPH. Because P-450 resides mainly in the microsomal fraction and is dependent on the presence of cofactors for catalytic activity, it seems that this oxidation is not catalyzed by cytochrome P-450.(ABSTRACT TRUNCATED AT 250 WORDS)

Human pharmacology of renzapride: a new gastrokinetic benzamide without dopamine antagonist properties

The activity of the substituted benzamide renzapride on the upper gastrointestinal tract has been investigated. It has been shown to enhance stomach emptying in normal subjects; doses of 2 and 5 mg decreasing by 21 and 37% respectively the volume of gastric contents aspirated 80 min after a test meal. Renzapride was found to reduce the oro-caecal transit time as assessed by the lactulose/breath hydrogen method in a dose related manner from 0.2 to 5 mg; the later dose producing a 62% reduction. Finally renzapride was shown not to elevate plasma prolactin at a dose of 5 mg, a finding consistent with lack of dopamine receptor antagonism.