Therapeutic Reviews aim to provide essential independent information for health professionals about drugs used in palliative and hospice care. Additional content is available on www.palliativedrugs.com. Country-specific books (Hospice and Palliative Care Formulary USA, and Palliative Care Formulary, British and Canadian editions) are also available and can be ordered from www.palliativebooks.com. The series editors welcome feedback on the articles ([email protected]).
Abbreviations/Key
b.i.d.Twice daily
CNSCentral nervous system
CYPCytochrome P450
GIGastrointestinal
OTCOver the counter (i.e., can be obtained without prescription)
POPer os, by mouth
p.r.n.Pro re nata, as needed/required
q2 hEvery 2 hours, etc.
q.i.d.Four times daily
Class: Antimotility drug.
Indications: Acute and chronic diarrhea, †ileostomy (to improve fecal consistency).
Contraindications: Colitis (ulcerative, infective, or antibiotic-associated).
Pharmacology
Loperamide is a potent μ-opioid receptor agonist.
1
Although well absorbed from the GI tract, loperamide is almost completely extracted and metabolized by cytochrome P450 in the liver (particularly CYP3A4) where it is conjugated, and the conjugates excreted in the bile. Because of this, little loperamide reaches the systemic circulation.The antidiarrheal action of loperamide results from direct absorption into the gut wall. Like morphine and other μ-receptor agonists, loperamide increases intestinal transit time by decreasing propulsive activity and increasing non-propulsive activity via its effect on the myenteric plexus in the longitudinal muscle layer.
2
, 3
Loperamide also increases anal sphincter tone and improves night-time continence in patients with ileo-anal pouches.4
Loperamide also modifies the intestinal transport of water and electrolytes by stimulating absorption,
5
and by an antisecretory action mediated by calmodulin antagonism, a property not shared by other opioids.6
, 7
, 8
Paradoxically, loperamide reduces the sodium-dependent uptake of glucose and other nutrients from the small bowel.
9
The development of tolerance to the GI effects of loperamide has been demonstrated in animal studies.10
However, loperamide has been successfully used in patients with chronic diarrhea for several years without evidence of tolerance.11
Loperamide is a substrate for P-glycoprotein, the efflux membrane transporter in the blood-brain barrier, and, although highly lipophilic,
3
loperamide is actively excluded from the CNS.12
, 13
Consequently, unlike morphine, which has both central and peripheral constipating effects, loperamide generally acts only peripherally1
(but see Drug interactions and Undesirable Effects).Loperamide has an effect on peripheral μ-opioid receptors activated by inflammation, and has been investigated as a possible topical analgesic for painful ulcers of the skin or mouth.
14
, 15
There are preliminary reports of the successful use of orodispersible tablets, e.g., Imodium® Instants (not USA), 2 mg q2–3 hp.r.n., as an adjuvant analgesic for oral pain arising from mucositis or cancer. However, the orodispersible tablets are relatively expensive. Theoretically, the oral solution is a possible alternative, but formulations which contain alcohol should not be used as this may exacerbate pain. Oral morphine solution (without alcohol) may be a better option, particularly long term.Unlike other drugs used for diarrhea, e.g., diphenoxylate and codeine, loperamide has no analgesic effect in therapeutic and supratherapeutic doses. The lack of CNS effects is one reason why loperamide is a popular first-line choice for the control of diarrhea, including when secondary to surgery, radiotherapy or chemotherapy.
17
, 18
However, octreotide (see a previous Therapeutic Review)
19
is recommended first-line for chemotherapy or radiotherapy-induced diarrhea when severe (i.e., an increase of ≥7 stools/24 h over baseline, hospital admission and IV fluids required for >24 h), and second-line for less severe diarrhea which does not respond to loperamide 16–24 mg/24 h.17
, 18
, 20
As an antidiarrheal, loperamide is about 3 times more potent mg for mg than diphenoxylate and 50 times more potent than codeine.
21
It is longer acting and, if used regularly, generally needs to be given only b.i.d. However, its maximum therapeutic impact may not manifest for 16–24 h; this has implications for initial dosing.- Schuermans V.
- Van Lommel R.
- Dom J.
- Brugmans J.
Loperamide (R18553), a novel type of antidiarrhoeal agent. Part 6: clinical pharmacology. Placebo-controlled comparison of the constipating activity and safety of loperamide, diphenoxylate and codeine in normal volunteers.
Arzneimittelforschung. 1974; 24: 1653-1657
13
The following regimens are approximately equivalent:- •loperamide 2 mg b.i.d.
- •diphenoxylate 2.5 mg q.i.d. (in combined diphenoxylate and atropine tablets)
- •codeine phosphate 60 mg q.i.d.
Loperamide is available in a range of formulations. Orodispersible tablets (not USA), which melt on the tongue, are bioequivalent to the capsules and are preferred by some patients. A combination product with simethicone provides more rapid relief of diarrhea and abdominal discomfort from bloating in acute non-specific diarrhea than either loperamide or simethicone alone.
22
, 23
One suggested explanation is that the surfactant effect of simethicone enhances the contact of loperamide with the gut mucosa. However, both these formulations are only available OTC and are relatively expensive (see Supply).Bioavailability: <2%.
Onset of action: about 1 h; maximum effect 16–24 h.
24
Time to peak plasma concentration: 2.5 h (oral solution); 5 h (capsules).
25
Plasma half-life: 11 h.
25
Duration of action: up to 3 days.
11
Cautions
Severe hepatic impairment could increase plasma concentrations of loperamide and the risk of undesirable effects.
26
Drug Interactions
CYP3A4 inhibitors (e.g., erythromycin, fluconazole, ketoconazole, quinidine, ritonavir) can increase plasma concentrations of loperamide.
26
Inhibitors of P-glycoprotein (e.g., cyclosporin, clarithromycin, erythromycin, intraconazole, ketoconazole, quinidine, ritonavir, verapamil) could potentially allow more loperamide to cross the blood-brain barrier and cause central opioid effects. Although one study in healthy volunteers of quinidine with loperamide found a blunted respiratory response to CO2 (indicating respiratory depression),
13
others have failed to demonstrate significant CNS effects.27
However, with typical doses of loperamide, it is unlikely that these interactions are clinically relevant.
27
Undesirable Effects
Ileus, fecal impaction, urinary retention. CNS effects can occur in children <2 years who receive excessive doses,
28
, 29
or in children after unintentional overdose (e.g., drowsiness).30
If necessary, use naloxone to reverse these effects.A patient on clozapine (an atypical antipsychotic) died of toxic megacolon after taking loperamide during an episode of food poisoning. Additive inhibition of intestinal motility was considered the precipitating cause.
31
Dose and Use
Ensure that the diarrhea is not secondary to fecal impaction.
Acute diarrhea
- •start with 4 mg PO stat
- •continue with 2 mg after each loose bowel action for up to 5 days
- •maximum recommended dose 16 mg/24 h.
Chemotherapy- or radiotherapy-induced diarrhea
- •if mild–moderate, give 4 mg stat and 2 mg after each loose bowel action
- •if not responding to doses of 24 mg/24 h, switch to octreotide
- •if severe, use octreotide first-line.
Chronic diarrhea
If symptomatic treatment is appropriate, the same initial approach is used for 2–3 days, after which a prophylactic b.i.d. regimen is instituted based on the needs of the patient during the previous 24 h, plus 2 mg after each loose bowel action. The effective dose varies widely. In palliative care, it is occasionally necessary to increase the dose to as much as 32 mg/24 h; this is twice the recommended maximum daily dose.
Supply
Loperamide (generic)
Tablets 2 mg, 28 days @ 2 mg q.i.d.=$8 OTC.
Capsules 2 mg, 28 days @ 2 mg q.i.d=$11.
Oral solution 1 mg/5 mL, 28 days @ 2 mg q.i.d.=$51 OTC.
Imodium® A-D (Janssen); all OTC
Caplets (capsule-shaped tablets) 2 mg, 28 days @ 2 mg q.i.d.=$27.
Tablets chewable 2 mg, 28 days @ 2 mg q.i.d.=$145.
Oral solution 1 mg/5 mL, 28 days @ 2 mg q.i.d.=$70.
Combination products with simethicone
Imodium® Multi-Symptom Relief (McNeil); all OTC
Caplets (capsule-shaped tablets) loperamide 2 mg, simethicone 125 mg, 28 days @ 1 q.i.d.=$56.
Tablets chewable loperamide 2 mg, simethicone 125 mg, 28 days @ 1 q.i.d.=$162.
References
- Comparison of the peripheral and central effects of the opioid agonists loperamide and morphine in the formalin test in rats.Neuropharmacology. 2001; 42: 253-261
- Distribution of loperamide in the intestinal wall.Biochem Pharmacol. 1979; 28: 1433-1434
- Mechanisms of action of loperamide.Scand J Gastroenterol Suppl. 1984; 96: 145-155
- Loperamide improves anal sphincter function and continence after restorative proctocolectomy.Dig Dis Sci. 1994; 39: 2612-2618
- Autoradiographic demonstration of [3H] loperamide binding to opioid receptors in rat and human small intestine.Prog Clin Biol Res. 1990; 328: 165-169
- Loperamide and calmodulin.Lancet. 1982; 1: 283
- Relationship between anti-diarrheal activity and binding to calmodulin.Eur J Pharmacol. 1982; 78: 375-377
- Loperamide: novel effects on capacitative calcium influx.Cell Mol Life Sci. 2000; 57: 149-157
- Effect of loperamide on Na+/D-glucose cotransporter activity in mouse small intestine.J Pharm Pharmacol. 2000; 52: 679-686
- Development of tolerance to the inhibitory effect of loperamide on gastrointestinal transit in mice.Eur J Pharm Sci. 2003; 20: 357-363
- Loperamide: a review of its pharmacological properties and therapeutic efficacy in diarrhoea.Drugs. 1978; 15: 33-52
- Loperamide (R 18553), a novel type of antidiarrheal agent. Part 5: The pharmacokinetics of loperamide in rats and man.Arzneimittelforschung. 1974; 24: 1649-1653
- Increased drug delivery to the brain by P-glycoprotein inhibition.Clin Pharmacol Ther. 2000; 68: 231-237
- Characterization of the antihyperalgesic action of a novel peripheral mu-opioid receptor agonist – loperamide.Anesthesiology. 1999; 90: 225-234
- Potential utility of peripherally applied loperamide in oral chronic graft-versus-host disease related pain.Jpn J Clin Oncol. 2008; 38: 857-860
- Personal communication.St. Oswald's Hospice, Newcastle2011
- Recommended guidelines for the treatment of cancer treatment-induced diarrhea.J Clin Oncol. 2004; 22: 2918-2926
- Prevention and management of chemotherapy-induced diarrhea in patients with colorectal cancer: a consensus statement by the Canadian Working Group on Chemotherapy-Induced Diarrhea.Curr Oncol. 2007; 14: 13-20
- Octreotide. J Pain Symptom Manage. 2010; 40: 142-148
- Octreotide in chemotherapy induced diarrhoea in colorectal cancer: a review article.Acta Gastroenterol Belg. 2009; 72: 289-295
- Loperamide (R18553), a novel type of antidiarrhoeal agent. Part 6: clinical pharmacology. Placebo-controlled comparison of the constipating activity and safety of loperamide, diphenoxylate and codeine in normal volunteers.Arzneimittelforschung. 1974; 24: 1653-1657
- Loperamide-simethicone vs loperamide alone, simethicone alone, and placebo in the treatment of acute diarrhea with gas-related abdominal discomfort. A randomized controlled trial.Arch Fam Med. 1999; 8: 243-248
- Randomized, double-blind, placebo-controlled clinical trial of loperamide plus simethicone versus loperamide alone and simethicone alone in the treatment of acute diarrhea with gas-related abdominal discomfort.Curr Med Res Opin. 2007; 23: 1033-1043
- Loperamide oxide in acute diarrhoea: a double-blind placebo-controlled trial.Aliment Pharmacol Ther. 1995; 9: 441-446
- Human pharmacokinetics and comparative bioavailability of loperamide hydrochloride.J Clin Pharmacol. 1979; 19: 211-218
- Loperamide: a pharmacological review.Rev Gastroenterol Dis. 2007; 7: s11-18
- Loperamide and P-glycoprotein inhibition: assessment of the clinical relevance.J Pharm Pharmacol. 2010; 62: 401-412
- Loperamide overdose managed by naloxone.Lancet. 1980; 1: 1413
- Loperamide toxicity in a child after a single dose.Br Med J (Clin Res Ed). 1987; 294: 1383
- Surveillance of loperamide ingestions: an analysis of 216 poison center reports.J Toxicol Clin Toxicol. 1997; 35: 11-19
- Lethal gastroenteritis associated with clozapine and loperamide.Am J Psychiatry. 2003; 160: 2242-2243
Article info
Publication history
Published online: June 23, 2011
Accepted:
April 21,
2011
AHFS 56:08Footnotes
Series Co-Editors: Andrew Wilcock, DM, FRCP, and Robert Twycross, DM, FRCP
Identification
Copyright
© 2011 Published by Elsevier Inc.