Drug Interactions between Etrafon Forte and Reglan

CONTRAINDICATED: Coadministration of metoclopramide with phenothiazines, neuroleptics, or other antidopaminergic agents (e.g., tetrabenazine) may increase the frequency and severity of extrapyramidal reactions (i.e., acute dystonic reactions, tardive dyskinesia, akathisia, Parkinson-like symptoms) due to additive antidopaminergic effects. By itself, metoclopramide can cause acute dystonic reactions in approximately 0.2% of patients treated with the usual adult dosages of 30 to 40 mg/day. These reactions are typically seen during the first 24 to 48 hours of treatment, occur more frequently in pediatric and adult patients less than 30 years of age, and are increased with higher dosages. Symptoms may include involuntary movements of limbs, facial grimacing, torticollis, oculogyric crisis, rhythmic protrusion of tongue, bulbar type of speech, trismus, opisthotonus (tetanus-like reactions), and rarely, stridor and dyspnea due to laryngospasm. Dystonic reactions usually respond to treatment with anticholinergic agents such as diphenhydramine or benztropine. Tardive dyskinesia (TD) is a potentially irreversible and disfiguring disorder characterized most frequently by involuntary movements of the tongue, face, mouth, or jaw, and less frequently by involuntary movements of the trunk and/or extremities. Movements may be choreoathetotic in appearance. Although the risk of TD with metoclopramide has not been extensively studied, a prevalence of 20% has been reported in one study among patients treated for at least 12 weeks. The risk is increased in the elderly, women, and diabetic populations; however, it is not possible to predict which patients will develop TD. Both the risk of developing TD and the likelihood that TD will become irreversible increase with duration of treatment and total cumulative dose. There is no known effective treatment. In some patients, TD may remit, partially or completely, within several weeks to months after metoclopramide is withdrawn. Akathisia, or motor restlessness, consist of feelings of anxiety, agitation, jitteriness, and insomnia, as well as inability to sit still, pacing, and foot tapping. Symptoms may disappear spontaneously or respond to a reduction in dosage. Parkinsonian-like symptoms may include bradykinesia, tremor, cogwheel rigidity, and mask-like facies. These symptoms most commonly occur within the first 6 months of metoclopramide therapy and subside within 2 to 3 months following drug discontinuation.

MANAGEMENT: Due to the potential for increased risk of serious and potentially irreversible extrapyramidal reactions, metoclopramide should not be prescribed in combination with other antidopaminergic agents. In addition, metoclopramide should not be used for longer than 12 weeks except in rare cases where therapeutic benefit is anticipated to outweigh the risk of developing tardive dyskinesia.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: Coadministration of a phenothiazine with a tricyclic antidepressant (TCA) may result in elevated plasma concentrations of one or both drugs as well as additive adverse effects. Most phenothiazines and TCAs have been found to undergo metabolism by CYP450 2D6, thus competitive inhibition of the enzyme may occur when more than one of these agents are administered. Although these drugs have been used together clinically, the possibility of increased risk of serious adverse effects such as central nervous system depression, tardive dyskinesia, hypotension, and prolongation of the QT interval should be considered, as many of these agents alone can and have produced these effects. In addition, excessive anticholinergic effects may occur in combination use, which can result in paralytic ileus, hyperthermia, heat stroke, and the anticholinergic intoxication syndrome. Peripheral symptoms of anticholinergic intoxication commonly include mydriasis, blurred vision, flushed face, fever, dry skin and mucous membranes, tachycardia, urinary retention, and constipation. Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures.

MANAGEMENT: Concurrent use of phenothiazines and TCAs should be approached with caution, particularly in the elderly and those with underlying organic brain disease, who tend to be more sensitive to the central anticholinergic effects of these drugs and in whom toxicity symptoms may be easily overlooked. Patients should be advised to notify their physician promptly if they experience potential symptoms of anticholinergic intoxication (e.g., abdominal pain, fever, heat intolerance, blurred vision, confusion, hallucinations) or cardiovascular toxicity (e.g., dizziness, palpitations, arrhythmias, syncope). Ambulatory patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them. A dosage reduction in one or both drugs may be necessary if excessive adverse effects develop.

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