Dosing and uses of Lomotil, Lonox (diphenoxylate-hcl-atropine)
Adult dosage forms and strengths
diphenoxylate HCl/atropine
oral solution: Schedule V
- (2.5mg/0.025mg)/5mL
tablet/capsule: Schedule V
- 2.5mg/0.025mg
Diarrhea
5 mg diphenoxylate/0.05 mg atropine PO q6hr; not to exceed 20 mg diphenoxylate daily
Maintenance: As low as ¼ of initial dosage
Pediatric dosage forms and strengths
diphenoxylate HCl/atropine
oral solution: Schedule V
- (2.5mg/0.025mg)/5mL
tablet/capsule: Schedule V
- 2.5mg/0.025mg
Diarrhea
<2 years: Safety and efficacy not established
2-12 years (use liquid only): diphenoxylate 0.3-0.4 mg/kg/day divided q6hr PO; not to exceed 10 mg/day
>12 years: 5 mg diphenoxylate/0.05 mg atropine PO q6hr; not to exceed 20 mg diphenoxylate daily
Maintenance: As low as ¼ of initial dosage
Lomotil, Lonox (diphenoxylate-hcl-atropine) adverse (side) effects
1-10%
Anticholinergic effects
Blurred vision
Sedation
Nausea
Vomiting
Abdominal discomfort
Dryness of skin or mouth
Frequency not defined
Pancreatitis
Toxic megacolon
Warnings
Contraindications
Hypersensitivity to diphenoxylate or atropine
Obstructive jaundice
Diarrhea associated with pseudomembranous enterocolitis or infectious enterotoxin-producing bacteria
Cautions
Hepatorenal disease and abnormal liver function
Ulcerative colitis
Improvement of symptoms expected within 48 hours; if no improvement within this time, drug is unlikely to be effective
Do not exceed recommended dosage; reduce initial dosage for maintenance
Renal impairment
Hepatic impairment
Pregnancy and lactation
Pregnancy category: C
Lactation: Atropine and, possibly, diphenoxylate metabolite distributed into breast milk; use with caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Lomotil, Lonox (diphenoxylate-hcl-atropine)
Mechanism of action
Diphenoxylate: Acts on smooth muscle of intestinal tract, inhibiting GI motility and excessive GI propulsion (like morphine)
Atropine: Subtherapeutic quantity of atropine is added to discourage deliberate overdose of diphenoxylate
Absorption
Onset: 45 min-1 hr
Duration: 3-4 hr
Peak plasma time: 2 hr
Bioavailability: 90%
Distribution
Vd: 324.2 L
Metabolism
Extensively metabolized in liver to active metabolite, diphenoxylic acid (difenoxin), which is 5 times more potent than diphenoxylate
Metabolites: Diphenoxylic acid (active), hydroxydiphenoxylic acid (inactive)
Elimination
Half-life: 2.5 hr (diphenoxylate); 3-14 hr (diphenoxylic acid)
Renal clearance: 1483 mL/min
Excretion: Feces via bile (49%), urine (14%)
