Products
Loperamide is commercially available in the form of capsules, film-coated tablets, melting tablets, and as a syrup (Imodium, generic). It has been approved in many countries since 1977.
Structure and properties
Loperamide (C29H33ClN2O2, Mr = 477.0 g/mol) is a piperidine derivative and has structural similarities to the neuroleptic haloperidol and the peristaltic inhibitor diphenoxylate. It exists as loperamide hydrochloride, a white powder that is sparingly soluble in water.
Effect
Loperamide (ATC A07DA03) has antidiarrheal properties. It binds with high affinity to μ-opioid receptors in the intestinal wall, thereby inhibiting propulsive peristalsis and prolonging the residence time of stool in the intestine. It is characterized by a rapid onset of action and a long duration of action. Loperamide has little to no central effects due to its high intestinal affinity, high first-pass metabolism, and as a substrate of P-glycoprotein at the blood–brain barrier.
Indication
For symptomatic treatment of acute and chronic diarrhea of various causes.
Dosage
According to the SmPC. Adults take 2 mg twice initially for acute diarrhea. An additional 2 mg may be administered after each additional liquid stool. The maximum daily dose is 16 mg (8 units).
Abuse
Loperamide can be abused as an intoxicant at very high doses. Abuse is dangerous because prolongation of the QT interval may result.
Contraindications
- Hypersensitivity
- Children under 2 years
- Severe liver dysfunction
Full precautions can be found in the drug label.
Interactions
Loperamide is a substrate of P-glycoprotein and is metabolized by CYP3A4 and CYP2C8. Corresponding drug-drug interactions with inhibitors and inducers are possible. CYP and P-gp inhibition have the potential to induce central opioid effects.
Adverse effects
The most common possible adverse effects include constipation, flatulence, headache, nausea, and dizziness.
