Drug Interactions for Motofen
Since the chemical structure of difenoxin hydrochloride is similar to meperidine hydrochloride, the concurrent use of MOTOFEN® with monoamine oxidase inhibitors may, in theory, precipitate a hypertensive crisis.
MOTOFEN® may potentiate the action of barbiturates, tranquilizers, narcotics, and alcohol. When these medications are used concomitantly with MOTOFEN®, the patient should be closely monitored.
Diphenoxylate hydrochloride, from which the principal active metabolite difenoxin is derived, was found to inhibit the hepatic microsomal enzyme system at a dose of 2 mg/kg/day in studies conducted with male rats. Therefore, difenoxin has the potential to prolong the biological half-lives of drugs for which the rate of elimination is dependent on the microsomal drug metabolizing enzyme system.
Drug Abuse And Dependence
MOTOFEN® tablets are a Schedule IV controlled substance.
Addiction to (dependence on) difenoxin hydrochloride is theoretically possible at high dosage. Therefore, the recommended dosage should not be exceeded. Because of the structural and pharmacological similarities of difenoxin hydrochloride to drugs with a definite addiction potential, MOTOFEN® should be administered with considerable caution to patients who are receiving addicting drugs, to individuals known to be addiction prone, or to those in whom histories suggest may increase dosage on their own initiative.
Diagnosis And Treatment
In the event of overdosage (initial signs may include dryness of the skin and mucous membranes, flushing, hyperthermia and tachycardia followed by lethargy or coma, hypotonic reflexes, nystagmus, pinpoint pupils and respiratory depression) gastric lavage, establishment of a patent airway and possibly mechanically assisted respiration are advised.
The narcotic antagonist naloxone may be used in the treatment of respiratory depression caused by narcotic analgesics of pharmacologically related compounds such as MOTOFEN® tablets. When naloxone is administered intravenously, the onset of action is generally apparent within two minutes. Naloxone may be administered subcutaneously or intramuscularly providing a slightly less rapid onset of action but a more prolonged effect.
To counteract respiratory depression caused by MOTOFEN® overdosage, the following dosage schedule for naloxone should be followed:
Adult Dosage: The usual initial adult dose of naloxone is 0.4 mg (one mL) administered intravenously. If respiratory function does not adequately improve after the initial dose, the same IV dose may be repeated at two-to-three minute intervals.
Children: The usual adult dose of naloxone for children is 0.01 mg/kg of body weight administered intravenously and repeated at two-to-three minute intervals if necessary.
Since the duration of action of difenoxin hydrochloride is longer than that of naloxone, improvement of respiration following administration may be followed by recurrent respiratory depression. Consequently, continuous observation is necessary until the effect of difenoxin hydrochloride on respiration (which effect may persist for many hours) has passed. Supplemental intramuscular doses of naloxone may be utilized to produce a longer lasting effect. TREAT ALL POSSIBLE MOTOFEN® OVERDOSAGES AS SERIOUS AND MAINTAIN MEDICAL OBSERVATION FOR AT LEAST 48 HOURS, PREFERABLY UNDER CONTINUOUS HOSPITAL CARE.
Although signs of overdosage and respiratory depression may not be evident soon after ingestion of difenoxin hydrochloride, respiratory depression may occur from 12 to 30 hours later.