Loperamide inhibits the peristaltic activity of longitudinal and circular smooth muscle in the intestine by interacting with cholinergic and noncholinergic neuronal mechanisms responsible for producing the peristaltic reflex. Loperamide binds to the opiate receptor in the gut wall, reducing propulsive peristalsis, and increase intestinal transit time.
Loperamide is orally administered capsule. After administration absorption is more than 65% which occurs at a modest rate, with peak serum levels of 2-3 µgm/litre occurring at about 4 hours later after oral administration. The rest 35% is excreted unchanged in the faeces. Loperamide undergoes an extensive presystemic first pass metabolism in the gut wall and in the liver. Loperamide does not act centrally due to its high affinity for the gut wall and its presystemic metabolism. This is why it reaches the systemic circulation in very minute amount. The route of elimination is 0.63-1.4% in urine as unchanged drug, 58% is excreted in the bile and 15-23% appears in the faeces.
Dosage & Administration
The initial dose is 2 capsules for adults and 1 capsule for children older than eight; in addition 1 capsule should be taken at any subsequent loose stool. The daily dose, however should not exceed 8 capsules for adults, for children 4-6 capsules according to age.
- Adults: 2 capsules daily.
- Children older than eight: 1 capsule daily.
Maintenance dose: One should aim at obtaining normal stools (e.g., one or two stools of good consistency a day). For this it may be necessary to adjust the initial dose (by increasing or decreasing it as required). Maintenance dose as a rule will vary from 1 to 6 capsules daily
Pregnancy & Lactation
Symptoms: CNS depression; constipation, urinary retention and ileus may occur.
Management: Employ gastric lavage followed by admin of activated charcoal. Naloxone HCl may be given as antidote.