Diphenoxylate/atropine

Administration

• Type: Antidiarrheal, opioid analog/anticholinergic
• Dosage Forms:
• Routes of Administration: PO
• Common Trade Names: Lomotil

Adult Dosing

• 5 mg diphenoxylate/0.05 mg atropine PO q6hr

Pediatric Dosing

• <2y: Safety/efficacy not established
• 2-13y: 0.3-0.4 mg diphenoxylate/kg/day in 4 divided doses

Special Populations

Pregnancy Rating

• Category C

Lactation risk

• "Exercise caution when drug is administered to nursing woman, since physicochemical characteristics of major metabolite, diphenoxylic acid, are such that it may be excreted in breast milk and since it is known that atropine is excreted in breast milk"

Renal Dosing

• Use caution

Hepatic Dosing

• Use caution; may precipitate hepatic coma

Contraindications

• Allergy to class/drug
• Obstructive jaundice
• Diarrhea due to pseudomembranous enterocolitis or infectious enterotoxin-producing bacteria (e.g. c. diff)
• Tablets only: children age <6y (risk of respiratory/CNS depression)
• Concomitant MAOI therapy

Adverse Reactions

Serious

• Severe respiratory depression
• Coma
• Exacerbation of dehydration and electrolyte imbalances due to intestinal fluid retention secondary to inhibition of peristalsis
• Bacterial overgrowth, release of bacterial endotoxins, sepsis
• Toxic megacolon
• Anticholinergic toxicity (hyperthermia, tachycardia, urinary retention, flushing, dry skin/mucous membranes), particularly in pediatric patients with Down's syndrome
• Pancreatitis

Common

• Nausea/vomiting, abdominal discomfort
• Blurred vision
• Sedation
• Dry skin or mouth

Pharmacology

• Half-life: 2.5-14h
• Metabolism: Hepatic
• Excretion: Urine/feces

Mechanism of Action

• Diphenoxylate: opioid analog of meperidine, inhibits GI motility and excessive GI propulsion
• Atropine: Subtherapeutic quantity added to discourage deliberate overdose of diphenoxylate

See Also

• Lomotil toxicity
• Diarrhea
• Opioids