2.1 Important Administration Instructions

Avoid treatment with metoclopramide for longer than 12 weeks because of the increased risk of developing TD with longer-term use [ see Dosage and Administration ( 2.2, 2.3), Warnings and Precautions ( 5.1) ].

2.2 Dosage for Gastroesophageal Reflux

Metoclopramide tablets may be administered continuously or intermittently in patients with symptomatic gastroesophageal reflux who fail to respond to conventional therapy:Metoclopramide tablets may be administered continuously or intermittently in patients with symptomatic gastroesophageal reflux who fail to respond to conventional therapy:

Continuous Dosing

The recommended adult dosage of metoclopramide is 10 to 15 mg four times daily for 4 to 12 weeks. The treatment duration is determined by endoscopic response. Administer the dosage thirty minutes before each meal and at bedtime. The maximum recommended daily dosage is 60 mg.The recommended adult dosage of metoclopramide is 10 to 15 mg four times daily for 4 to 12 weeks. The treatment duration is determined by endoscopic response. Administer the dosage thirty minutes before each meal and at bedtime. The maximum recommended daily dosage is 60 mg.

Table 1 displays the recommended daily dosage and maximum daily dosage for adults and dosage adjustments for patients with moderate or severe hepatic impairment (Child-Pugh B or C), in patients with creatinine clearance less than 60 mL/minute, in cytochrome P450 2D6 (CYP2D6) poor metabolizers, and with concomitant use with strong CYP2D6 inhibitors.

Intermittent Dosing

If symptoms only occur intermittently or at specific times of the day, administer metoclopramide in single dose up to 20 mg prior to the provoking situation. Consider dosage reductions for the populations and situations in Table 1.If symptoms only occur intermittently or at specific times of the day, administer metoclopramide in single dose up to 20 mg prior to the provoking situation. Consider dosage reductions for the populations and situations in Table 1.

2.3 Dosage for Acute and Recurrent Diabetic Gastroparesis

The recommended adult dosage for the treatment of acute and recurrent diabetic gastroparesis is 10 mg four times daily for 2 to 8 weeks, depending on symptomatic response. Avoid metoclopramide treatment for greater than 12 weeks [ ]. Administer the dosage thirty minutes before each meal and at bedtime. The maximum recommended daily dosage is 40 mg. The recommended adult dosage for the treatment of acute and recurrent diabetic gastroparesis is 10 mg four times daily for 2 to 8 weeks, depending on symptomatic response. Avoid metoclopramide treatment for greater than 12 weeks [ see Warnings and Precautions ( 5.1) ]. Administer the dosage thirty minutes before each meal and at bedtime. The maximum recommended daily dosage is 40 mg.

Table 2 displays the recommended daily dosage and maximum daily dosage for adults and dosage adjustments for patients with moderate or severe hepatic impairment (Child-Pugh B or C), in patients with creatinine clearance less than 60 mL/minute, in cytochrome P450 2D6 (CYP2D6) poor metabolizers, and with concomitant use with strong CYP2D6 inhibitors.

If patients with diabetic gastroparesis have severe nausea or vomiting and are unable to take oral metoclopramide tablets, consider starting therapy with metoclopramide injection given intramuscularly or intravenously for up to 10 days (see the prescribing information for metoclopramide injection). After patients are able to take oral therapy, switch to metoclopramide tablets.If patients with diabetic gastroparesis have severe nausea or vomiting and are unable to take oral metoclopramide tablets, consider starting therapy with metoclopramide injection given intramuscularly or intravenously for up to 10 days (see the prescribing information for metoclopramide injection). After patients are able to take oral therapy, switch to metoclopramide tablets.

5.1 Tardive Dyskinesia

Metoclopramide can cause tardive dyskinesia (TD), a syndrome of potentially irreversible and disfiguring involuntary movements of the face or tongue, and sometimes of the trunk and/or extremities. Movements may be choreoathetotic in appearance. The risk of developing TD and the likelihood that TD will become irreversible increases with duration of treatment and total cumulative dosage. Additionally, the risk of developing TD is increased among the elderly, especially elderly women [ ], and in patients with diabetes mellitus. Due to the risk of developing TD, avoid treatment with metoclopramide for longer than 12 weeks and reduce the dosage in elderly patients [ ]. Metoclopramide can cause tardive dyskinesia (TD), a syndrome of potentially irreversible and disfiguring involuntary movements of the face or tongue, and sometimes of the trunk and/or extremities. Movements may be choreoathetotic in appearance. The risk of developing TD and the likelihood that TD will become irreversible increases with duration of treatment and total cumulative dosage. Additionally, the risk of developing TD is increased among the elderly, especially elderly women [ see Use in Specific Populations ( 8.5) ], and in patients with diabetes mellitus. Due to the risk of developing TD, avoid treatment with metoclopramide for longer than 12 weeks and reduce the dosage in elderly patients [ see Dosage and Administration ( 2.2, 2.3) ].

Discontinue metoclopramide immediately in patients who develop signs and symptoms of TD. There is no known effective treatment for established cases of TD, although in some patients TD may remit, partially or completely, within several weeks to months after metoclopramide is withdrawn.Discontinue metoclopramide immediately in patients who develop signs and symptoms of TD. There is no known effective treatment for established cases of TD, although in some patients TD may remit, partially or completely, within several weeks to months after metoclopramide is withdrawn.

Metoclopramide itself may suppress, or partially suppress, the signs of TD, thereby masking the underlying disease process. The effect of this symptomatic suppression upon the long-term course of TD is unknown. Metoclopramide is contraindicated in patients with a history of TD [ ]. Metoclopramide itself may suppress, or partially suppress, the signs of TD, thereby masking the underlying disease process. The effect of this symptomatic suppression upon the long-term course of TD is unknown. Metoclopramide is contraindicated in patients with a history of TD [ see Contraindications ( 4) ]. Avoid metoclopramide in patients receiving other drugs that are likely to cause TD (e.g., antipsychotics).

5.2 Other Extrapyramidal Symptoms

In addition to TD, metoclopramide may cause other extrapyramidal symptoms (EPS), parkinsonian symptoms, and motor restlessness. Advise patients to seek immediate medical attention if such symptoms occur and to discontinue metoclopramide.In addition to TD, metoclopramide may cause other extrapyramidal symptoms (EPS), parkinsonian symptoms, and motor restlessness. Advise patients to seek immediate medical attention if such symptoms occur and to discontinue metoclopramide.

• Extrapyramidal symptoms (EPS), such as acute dystonic reactions, occurred in patients treated with metoclopramide dosages of 30 mg to 40 mg daily. Such reactions occurred more frequently in adults less than 30 years of age and at higher than recommended dosages. EPS occurred more frequently in pediatric patients compared to adults (metoclopramide is not approved for use in pediatric patients). Symptoms can occur in the first 24 to 48 hours after starting metoclopramide. Symptoms included involuntary movements of limbs and facial grimacing, torticollis, oculogyric crisis, rhythmic protrusion of tongue, bulbar type of speech, trismus, or dystonic reactions resembling tetanus. Rarely, dystonic reactions were present as stridor and dyspnea, possibly due to laryngospasm. Diphenhydramine hydrochloride or benztropine mesylate may be used to treat these adverse reactions. Avoid metoclopramide in patients receiving other drugs that can cause EPS (e.g., antipsychotics).Avoid metoclopramide in patients receiving other drugs that can cause EPS (e.g., antipsychotics).Extrapyramidal symptoms (EPS), such as acute dystonic reactions, occurred in patients treated with metoclopramide dosages of 30 mg to 40 mg daily. Such reactions occurred more frequently in adults less than 30 years of age and at higher than recommended dosages. EPS occurred more frequently in pediatric patients compared to adults (metoclopramide is not approved for use in pediatric patients). Symptoms can occur in the first 24 to 48 hours after starting metoclopramide. Symptoms included involuntary movements of limbs and facial grimacing, torticollis, oculogyric crisis, rhythmic protrusion of tongue, bulbar type of speech, trismus, or dystonic reactions resembling tetanus. Rarely, dystonic reactions were present as stridor and dyspnea, possibly due to laryngospasm. Diphenhydramine hydrochloride or benztropine mesylate may be used to treat these adverse reactions. Avoid metoclopramide in patients receiving other drugs that can cause EPS (e.g., antipsychotics).Avoid metoclopramide in patients receiving other drugs that can cause EPS (e.g., antipsychotics).
• Parkinsonian symptoms (bradykinesia, tremor, cogwheel rigidity, mask-like facies) have occurred after starting metoclopramide, more commonly within the first 6 months, but also after longer periods. Symptoms generally have subsided within 2 to 3 months after discontinuation of metoclopramide. Avoid metoclopramide in patients with Parkinson’s disease and other patients being treated with antiparkinsonian drugs due to potential exacerbation of symptoms. Avoid treatment with metoclopramide for more than 12 weeks [ see Dosage and Administration ( 2.2, 2.3), Warnings and Precautions ( 5.1) ]. Avoid metoclopramide in patients with Parkinson’s disease and other patients being treated with antiparkinsonian drugs due to potential exacerbation of symptoms.see Dosage and Administration ( 2.2, 2.3), Warnings and Precautions ( 5.1) Parkinsonian symptoms (bradykinesia, tremor, cogwheel rigidity, mask-like facies) have occurred after starting metoclopramide, more commonly within the first 6 months, but also after longer periods. Symptoms generally have subsided within 2 to 3 months after discontinuation of metoclopramide. Avoid metoclopramide in patients with Parkinson’s disease and other patients being treated with antiparkinsonian drugs due to potential exacerbation of symptoms. Avoid treatment with metoclopramide for more than 12 weeks [ see Dosage and Administration ( 2.2, 2.3), Warnings and Precautions ( 5.1) ]. Avoid metoclopramide in patients with Parkinson’s disease and other patients being treated with antiparkinsonian drugs due to potential exacerbation of symptoms.see Dosage and Administration ( , ), Warnings and Precautions ( )
• Motor restlessness (akathisia) has developed and consisted of feelings of anxiety, agitation, jitteriness, and insomnia, as well as inability to sit still, pacing, and foot tapping. If symptoms resolve, consider restarting at a lower dosage.

5.3 Neuroleptic Malignant Syndrome

Metoclopramide may cause a potentially fatal symptom complex called neuroleptic malignant syndrome (NMS). Avoid metoclopramide in patients receiving other drugs associated with NMS, including typical and atypical antipsychotics. Metoclopramide may cause a potentially fatal symptom complex called neuroleptic malignant syndrome (NMS). NMS has been reported in association with metoclopramide overdosage and concomitant treatment with another drug associated with NMS. Avoid metoclopramide in patients receiving other drugs associated with NMS, including typical and atypical antipsychotics.

Clinical manifestations of NMS include hyperpyrexia, muscle rigidity, altered mental status, and manifestations of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac arrhythmias). Additional signs may include elevated creatine phosphokinase, myoglobinuria (rhabdomyolysis), and acute renal failure. Patients with such symptoms should be evaluated immediately.Clinical manifestations of NMS include hyperpyrexia, muscle rigidity, altered mental status, and manifestations of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac arrhythmias). Additional signs may include elevated creatine phosphokinase, myoglobinuria (rhabdomyolysis), and acute renal failure. Patients with such symptoms should be evaluated immediately.

In the diagnostic evaluation, consider the presence of other serious medical conditions (e.g., pneumonia, systemic infection) and untreated or inadequately treated extrapyramidal signs and symptoms. Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, malignant hyperthermia, drug fever, serotonin syndrome, and primary central nervous system pathology.In the diagnostic evaluation, consider the presence of other serious medical conditions (e.g., pneumonia, systemic infection) and untreated or inadequately treated extrapyramidal signs and symptoms. Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, malignant hyperthermia, drug fever, serotonin syndrome, and primary central nervous system pathology.

Management of NMS includes:Management of NMS includes:

• Immediate discontinuation of metoclopramide and other drugs not essential to concurrent therapy [ see Drug Interactions ( 7.1) ].
• Intensive symptomatic treatment and medical monitoring.
• Treatment of any concomitant serious medical problems for which specific treatments are available.

5.4 Depression

Depression has occurred in metoclopramide-treated patients with and without a history of depression. Symptoms have included suicidal ideation and suicide. Avoid metoclopramide use in patients with a history of depression.

5.5 Hypertension

Metoclopramide may elevate blood pressure. In one study in hypertensive patients, intravenously administered metoclopramide was shown to release catecholamines; hence, avoid use in patients with hypertension or in patients taking monoamine oxidase inhibitors [ see Drug Interactions ( 7.1) ].

There are also clinical reports of hypertensive crises in patients with undiagnosed pheochromocytoma. Metoclopramide is contraindicated in patients with pheochromocytoma or other catecholamine-releasing paragangliomas [ see Contraindications ( 4) ]. Discontinue metoclopramide in any patient with a rapid rise in blood pressure.

5.6 Fluid Retention

Because metoclopramide produces a transient increase in plasma aldosterone, patients with cirrhosis or congestive heart failure may be at risk of developing fluid retention and volume overload. Discontinue metoclopramide if any of these adverse reactions occur.

5.7 Hyperprolactinemia

As with other dopamine D 2 receptor antagonists, metoclopramide elevates prolactin levels.

Hyperprolactinemia may suppress hypothalamic GnRH, resulting in reduced pituitary gonadotropin secretion. This, in turn, may inhibit reproductive function by impairing gonadal steroidogenesis in both female and male patients. Galactorrhea, amenorrhea, gynecomastia, and impotence have been reported with prolactin-elevating drugs, including metoclopramide.

Hyperprolactinemia may potentially stimulate prolactin-dependent breast cancer. However, some clinical studies and epidemiology studies have not shown an association between administration of dopamine D 2 receptor antagonists and tumorigenesis in humans [ see Nonclinical Toxicology (13.1) ].

5.8 Effects of the Ability to Drive and Operate Machinery

Metoclopramide may impair the mental and/or physical abilities required for the performance of hazardous tasks such as operating machinery or driving a motor vehicle. Concomitant use of central nervous system (CNS) depressants or drugs associated with EPS may increase this effect (e.g., alcohol, sedatives, hypnotics, opiates, and anxiolytics). Avoid metoclopramide or the interacting drug, depending on the importance of the drug to the patient [ see Drug Interactions ( 7.1) ].

7.1 Effects of Other Drugs on Metoclopramide

Table 3 displays the effects of other drugs on metoclopramide.

7.2 Effects of Metoclopramide on Other Drugs

Table 4 displays the effects of metoclopramide on other drugs.

8.1 Pregnancy

Risk Summary

Published studies, including retrospective cohort studies, national registry studies, and meta-analyses, do not report an increased risk of adverse pregnancy-related outcomes with use of metoclopramide during pregnancy.

There are potential risks to the neonate following exposure in utero to metoclopramide during delivery [ see Clinical Considerations]. In animal reproduction studies, no adverse developmental effects were observed with oral administration of metoclopramide to pregnant rats and rabbits at exposures about 6 and 12 times the maximum recommended human dose (MRHD) [ see Data].

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defects, loss or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in the clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Clinical Considerations

Fetal/Neonatal Adverse Reactions

Metoclopramide crosses the placental barrier and may cause extrapyramidal signs and methemoglobinemia in neonates with maternal administration during delivery. Monitor neonates for extrapyramidal signs [ see Warnings and Precautions ( 5.1, 5.2), Use in Specific Populations ( 8.4) ].

Data

Animal Data

Reproduction studies have been performed following administration of oral metoclopramide during organogenesis in pregnant rats at about 6 times the MRHD calculated on body surface area and in pregnant rabbits at about 12 times the MRHD calculated on body surface area. No evidence of adverse developmental effects due to metoclopramide were observed.

8.2 Lactation

Risk Summary

Limited published data report the presence of metoclopramide in human milk in variable amounts. Breastfed infants exposed to metoclopramide have experienced gastrointestinal adverse reactions, including intestinal discomfort and increased intestinal gas formation [ see Data]. Metoclopramide elevates prolactin levels [ see Warnings and Precautions ( 5.7) ]; however, the published data are not adequate to support drug effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for metoclopramide and any potential adverse effects on the breastfed child from metoclopramide or from the underlying maternal condition.

Clinical Considerations

Monitor breastfeeding neonates because metoclopramide may cause extrapyramidal signs (dystonias) and methemoglobinemia [ see Warnings and Precautions ( 5.1, 5.2), Use in Specific Populations ( 8.4) ].

Data

In published clinical studies, the estimated amount of metoclopramide received by the breastfed infant was less than 10% of the maternal weight-adjusted dose. In one study, the estimated daily amount of metoclopramide received by infants from breast milk ranged from 6 to 24 mcg/kg/day in early puerperium (3 to 9 days postpartum) and from 1 to 13 mcg/kg/day at 8 to 12 weeks postpartum.

8.4 Pediatric Use

Metoclopramide is not recommended for use in pediatric patients due to the risk of tardive dyskinesia (TD) and other extrapyramidal symptoms as well as the risk of methemoglobinemia in neonates. The safety and effectiveness of metoclopramide in pediatric patients have not been established.

Dystonias and other extrapyramidal symptoms associated with metoclopramide are more common in pediatric patients than in adults [ see Warnings and Precautions ( 5.1, 5.2) ]. In addition, neonates have reduced levels of NADH-cytochrome b 5 reductase, making them more susceptible to methemoglobinemia, a possible adverse reaction of metoclopramide use in neonates [ see Use in Specific Populations ( 8.8) ].

8.5 Geriatric Use

Metoclopramide is known to be substantially excreted by the kidney, and the risk of adverse reactions, including tardive dyskinesia (TD), may be greater in patients with impaired renal function [ see Use in Specific Populations ( 8.6), Clinical Pharmacology ( 12.3) ]. Elderly patients are more likely to have decreased renal function and may be more sensitive to the therapeutic or adverse effects of metoclopramide; therefore, consider a reduced dosage of metoclopramide in elderly patients [ see Boxed Warning, Dosage and Administration ( 2.2, 2.3), Warnings and Precautions ( 5.1) ].

8.6 Renal Impairment

The clearance of metoclopramide is decreased and the systemic exposure is increased in patients with moderate to severe renal impairment compared to patients with normal renal function, which may increase the risk of adverse reactions. Reduce the metoclopramide dosage in patients with moderate and severe renal impairment (creatinine clearance less than or equal to 60 mL/minute), including those receiving hemodialysis and continuous ambulatory peritoneal dialysis [ see Dosage and Administration ( 2.2, 2.3), Clinical Pharmacology ( 12.3) ].

8.7 Hepatic Impairment

Patients with severe hepatic impairment (Child-Pugh C) have reduced systemic metoclopramide clearance (by approximately 50%) compared to patients with normal hepatic function. The resulting increase in metoclopramide blood concentrations increases the risk of adverse reactions. There is no pharmacokinetic data in patients with moderate hepatic impairment (Child-Pugh B). Reduce metoclopramide dosage in patients with moderate or severe (Child-Pugh B or C) hepatic impairment [ see Dosage and Administration ( 2.2, 2.3) ]. There is no dosage adjustment required for patients with mild hepatic impairment (Child-Pugh A).

In addition, metoclopramide, by producing a transient increase in plasma aldosterone, may increase the risk of fluid retention in patients with hepatic impairment [ see Warnings and Precautions ( 5.6) ].

Monitor patients with hepatic impairment for the occurrence of fluid retention and volume overload.

8.8 NADH-Cytochrome b 5 Reductase Deficiency

Metoclopramide-treated patients with NADH-cytochrome b 5 reductase deficiency are at an increased risk of developing methemoglobinemia and/or sulfhemoglobinemia. For patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency with metoclopramide-induced methemoglobinemia, methylene blue treatment is not recommended. Methylene blue may cause hemolytic anemia in patients with G6PD deficiency, which may be fatal [ see Overdosage ( 10) ].

8.9 CYP2D6 Poor Metabolizers

Metoclopramide is a substrate of CYP2D6. The elimination of metoclopramide may be slowed in patients who are CYP2D6 poor metabolizers (compared to patients who are CYP2D6 intermediate, extensive, or ultra-rapid metabolizers); possibly increasing the risk of dystonic and other adverse reactions to metoclopramide [ see Clinical Pharmacology ( 12.3) ]. Reduce the metoclopramide dosage in patients who are poor CYP2D6 metabolizers [ see Dosage and Administration ( 2.2, 2.3) ].

12.1 Mechanism of Action

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.

12.2 Pharmacodynamics

Gastroesophageal Reflux

In patients with gastroesophageal reflux and low lower esophageal sphincter pressure (LESP), single oral doses of metoclopramide produced dose-related increases in LESP. Effects began at about 5 mg and increased through 20 mg. The increase in LESP from a 5 mg dose lasted about 45 minutes and that of 20 mg lasted between 2 and 3 hours. Increased rate of stomach emptying was observed with single oral doses of 10 mg.

12.3 Pharmacokinetics

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 ( 2.2, 2.3), 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 ( 2.2, 2.3) 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 ( 2.2, 2.3) and Use in Specific Populations ( 8.7) ].

Drug Interaction Studies

Effect of Metoclopramide on CYP2D6 Substrates

Although in vitro studies suggest that metoclopramide can inhibit CYP2D6, metoclopramide is unlikely to interact with CYP2D6 substrates in vivo at 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 max and AUC 0-∞, respectively, compared to patients who received metoclopramide alone (see Table 5) [ see Drug Interactions ( 7.1) ].

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

A 77-week study was conducted in rats with oral metoclopramide doses up to 40 mg/kg/day (about six times the maximum recommended human dose on body surface area basis). Metoclopramide elevated prolactin levels and the elevation persisted during chronic administration. An increase in mammary neoplasms was found in rodents after chronic administration of metoclopramide [ see Warnings and Precautions ( 5.7) ]. In a rat model for assessing the tumor promotion potential, a 2-week oral treatment with metoclopramide at a dose of 260 mg/kg/day (about 35 times the maximum recommended human dose based on body surface area) enhanced the tumorigenic effect of N-nitrosodiethylamine.

Mutagenesis

Metoclopramide was positive in the in vitro Chinese hamster lung cell/HGPRT forward mutation assay for mutagenic effects and in the in vitro human lymphocyte chromosome aberration assay for clastogenic effects. It was negative in the in vitro Ames mutation assay, the in vitro unscheduled DNA synthesis assay with rat and human hepatocytes, and the in vivo rat micronucleus assay.

Impairment of Fertility

Metoclopramide at intramuscular doses up to 20 mg/kg/day (about three times the maximum recommended human dose based on body surface area) was found to have no effect on fertility and reproductive performance of male and female rats.