Metoclopramide Hcl 15 mg (CR) · Tablets

Metoclopramide stimulates motility of the upper gastrointestinal tract without stimulating gastric, biliary, or pancreatic secretions. The exact mechanism of action of metoclopramide in the treatment of gastroesophageal reflux and acute and recurrent diabetic gastroparesis has not been fully established. It seems to sensitize tissues to the action of acetylcholine. The effect of metoclopramide on motility is not dependent on intact vagal innervation, but it can be abolished by anticholinergic drugs.

Metoclopramide increases the tone and amplitude of gastric (especially antral) contractions, relaxes the pyloric sphincter and the duodenal bulb, and increases peristalsis of the duodenum and jejunum resulting in accelerated gastric emptying and intestinal transit. It increases the resting tone of the lower esophageal sphincter. It has little, if any, effect on the motility of the colon or gallbladder.

Absorption — Relative to an intravenous dose of 20 mg, the absolute bioavailability of oral metoclopramide is 80% ± 15.5% as demonstrated in a crossover study of 18 subjects. Peak plasma concentrations occurred at about 1 to 2 hours after a single oral dose. Similar time to peak was observed after individual doses at steady state.

In a single dose study of 12 subjects, the area under the drug concentration-time curve increased linearly with doses from 20 to 100 mg (5 times the maximum recommended single dose). Peak concentrations increased linearly with dose; time to peak concentrations remained the same; whole body clearance was unchanged; and the elimination rate remained the same. The mean elimination half-life in subjects with normal renal function was 5 to 6 hours. Linear kinetic processes adequately describe the absorption and elimination of metoclopramide.

Distribution — Metoclopramide is not extensively bound to plasma proteins (about 30%). The whole body volume of distribution is high (about 3.5 L/kg), which suggests extensive distribution of drug to the tissues.

Elimination — Metabolism:Metoclopramide undergoes enzymatic metabolism via oxidation as well as glucuronide and sulfate conjugation reactions in the liver. Monodeethylmetoclopramide, a major oxidative metabolite, is formed primarily by CYP2D6, an enzyme subject to genetic variability [see Dosage and Administration ( 2.1 , 2.2 ), Use in Specific Populations ( 8.9)] .

Excretion:Approximately 85% of the radioactivity of an orally administered dose appeared in the urine within 72 hours. After oral administration of 10 or 20 mg, a mean of 18% and 22% of the dose, respectively, was recovered as free metoclopramide in urine within 36 hours.

Specific Populations — Patients with Renal Impairment:In a study of 24 patients with varying degrees of renal impairment (moderate, severe, and end-stage renal disease (ESRD) requiring dialysis), the systemic exposure (AUC) of metoclopramide in patients with moderate to severe renal impairment was about 2-fold the AUC in subjects with normal renal function. The AUC of metoclopramide in patients with ESRD on dialysis was about 3.5-fold the AUC in subjects with normal renal function [see Dosage and Administration ( 2.1 , 2.2 ) and Use in Specific Populations ( 8.6)] .

Patients with Hepatic Impairment:In a group of 8 patients with severe hepatic impairment (Child-Pugh C), the average metoclopramide clearance was reduced by approximately 50% compared to patients with normal hepatic function [see Dosage and Administration ( 2.1 , 2.2 ) and Use in Specific Populations ( 8.7)] .

Effect of Metoclopramide on CYP2D6 Substrates — Although in vitrostudies suggest that metoclopramide can inhibit CYP2D6, metoclopramide is unlikely to interact with CYP2D6 substrates in vivoat therapeutically relevant concentrations.

Effect of CYP2D6 Inhibitors on Metoclopramide — In healthy subjects, 20 mg of metoclopramide and 60 mg of fluoxetine (a strong CYP2D6 inhibitor) were administered, following prior exposure to 60 mg fluoxetine orally for 8 days. The patients who received concomitant metoclopramide and fluoxetine had a 40% and 90% increase in metoclopramide C maxand AUC 0-∞, respectively, compared to patients who received metoclopramide alone (see Table 5) [see Drug Interactions ( 7.1)] .