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Systematic (IUPAC) name
4-[4-(4-chlorophenyl)-4-hydroxypiperidin-1-yl]- N,N-dimethyl-2,2-diphenylbutanamide
Clinical data
Trade names Imodium
AHFS/Drugs.com monograph
MedlinePlus a682280
Pregnancy cat. B3 (AU) C (US)
Legal status Pharmacy Only (S2) (AU) OTC (CA) GSL (UK) OTC (US)
Routes oral, insufflation
Pharmacokinetic data
Bioavailability 0.3%
Protein binding 97%
Metabolism Hepatic (extensive)
Half-life 7-14 hours
Excretion Faeces (30-40%), urine (1%)
CAS number 53179-11-6 YesY
34552-83-5 (with HCl)
ATC code A07DA03
A07DA05 (oxide)
PubChem CID 3955
DrugBank DB00836
ChemSpider 3818 YesY
KEGG D08144 YesY
Synonyms R-18553
Chemical data
Formula C29H33ClN2O2 
Mol. mass 477.037 g/mol (513.506 with HCl)
 N (what is this?)  (verify)

Loperamide /lˈpɛrəmd/, a piperidine derivative,[1] is a drug used against diarrhoea resulting from gastroenteritis or inflammatory bowel disease. It was developed by Janssen in 1971.[2] In most countries it is available generically and under brand names such as Lopex, Imodium, Dimor, Fortasec, Lopedium, Gastro-Stop and Pepto Diarrhea Control. It was developed at Janssen Pharmaceutica.[3]

Medical uses[edit]

Loperamide is effective for the treatment of a number of types of diarrhea.[4]

Mechanism of action[edit]

Ball-and-stick model of loperamide molecule

Loperamide is an opioid-receptor agonist and acts on the μ-opioid receptors in the myenteric plexus of the large intestine; by itself it does not affect the central nervous system. It works similarly to morphine, by decreasing the activity of the myenteric plexus, which in turn decreases the tone of the longitudinal and circular smooth muscles of the intestinal wall.[5][6] This increases the amount of time substances stay in the intestine, allowing for more water to be absorbed out of the fecal matter. Loperamide also decreases colonic mass movements and suppresses the gastrocolic reflex.[7]

Ability to cross the blood–brain barrier[edit]

It is a misconception that loperamide does not cross the blood–brain barrier. Loperamide does cross this barrier, although it is immediately pumped back out into non–central nervous system (CNS) circulation by P-glycoprotein. While this mechanism effectively shields the CNS from exposure (and thus risk of CNS tolerance/dependence) to loperamide, many drugs are known to inhibit P-glycoprotein and may thus render the CNS vulnerable to opiate agonism by loperamide.[8]

Concurrent administration of P-glycoprotein inhibitors such as quinidine and its other isomer quinine (although much higher doses must be used), PPIs like omeprazole (Prilosec OTC) and even black pepper (piperine as the active ingredient) could potentially allow loperamide to cross the blood–brain barrier. It should however be noted that only quinidine with loperamide was found to produce respiratory depression, indicative of central opioid action.[9]

Loperamide has been shown to cause a mild physical dependence during preclinical studies, specifically in mice, rats, and rhesus monkeys. Symptoms of mild opiate withdrawal have been observed following abrupt discontinuation of long-term therapy with loperamide.[10][11]


The use of loperamide (Imodium) in children under 2 years is not recommended. There have been rare reports of fatal paralytic ileus associated with abdominal distention. Most of these reports occurred in the setting of acute dysentery, overdose, and with very young children less than two years of age.[12] In 1990, all pediatric formulations of the antidiarrheal loperamide (Imodium and others) were banned in Pakistan.[13]

Treatment should be avoided in the presence of high fever or if the stool is bloody (dysentery).[14] It is of no value in diarrhea caused by cholera, Shigella or Campylobacter.[14] Treatment is not recommended for patients that could suffer detrimental effects from rebound constipation. If there is a suspicion of diarrhea associated with organisms that can penetrate the intestinal walls, such as E. coli O157:H7 or salmonella, loperamide is contraindicated.[15][16]

Loperamide treatment is not used in symptomatic C. difficile infections, as it increases the risk of toxin retention and precipitation of toxic megacolon.

Loperamide is not recommended in the UK for use during pregnancy nor by nursing mothers.[17] In the US, loperamide is classified by the FDA as pregnancy category B, and should be used only for 24 hours and after 12 weeks of gestation.[18]

Loperamide should be administered with caution to patients suffering from hepatic impairment due to reduced first pass metabolism.[19]

Adverse effects[edit]

Adverse drug reactions (ADRs) associated with loperamide include abdominal pain and bloating, nausea, vomiting and constipation. Rare side-effects associated with loperamide are paralytic ileus, dizziness and rashes.In high doses, loperamide in conjunction with Cimetadine, can cause ventricular fibrillation and death.[20]

The most frequent symptoms of loperamide overdose are drowsiness, vomiting and abdominal pain or burning.[21]


It is not recommended for use in hepatic failure since it can precipitate hepatic encephalopathy.[20]

See also[edit]


  1. ^ US National Cancer Institute, Drug Dictionary
  2. ^ US Patent Janssen US3714159
  3. ^ Stokbroekx, R. A.; Vanenberk, J.; Van Heertum, A. H. M. T.; Van Laar, G. M. L. W.; Van der Aa, M. J. M. C.; Van Bever, W. F. M.; Janssen, P. A. J. (1973). "Synthetic Antidiarrheal Agents. 2,2-Diphenyl-4-(4'-aryl-4'-hydroxypiperidino)butyramides". Journal of Medicinal Chemistry 16 (7): 782–786. doi:10.1021/jm00265a009. 
  4. ^ Hanauer, S. B. (Winter 2008). "The Role of Loperamide in Gastrointestinal Disorders". Reviews in Gastroenterological Disorders 8 (1): 15–20. PMID 18477966. 
  5. ^ http://www.drugbank.ca/drugs/DB00836
  6. ^ http://www.drugs.com/mmx/loperamide-hydrochloride.html
  7. ^ Katzung, B. G. (2004). Basic and Clinical Pharmacology (9th ed.). ISBN 0-07-141092-9. [page needed]
  8. ^ Upton, R. N. (2007). "Cerebral Uptake of Drugs in Humans". Clinical and Experimental Pharmacology and Physiology 34 (8): 695–701. doi:10.1111/j.1440-1681.2007.04649.x. PMID 17600543.  edit
  9. ^ Sadeque, A. J.; Wandel, C.; He, H.; Shah, S.; Wood, A. J. (September 2000). "Increased Drug Delivery to the Brain by P-glycoprotein Inhibition". Clinical Pharmacology and Therapeutics 68 (3): 231–237. doi:10.1067/mcp.2000.109156. PMID 11014404. 
  10. ^ Yanagita, T.; Miyasato, K.; Sato, J. (1979). "Dependence Potential of Loperamide Studied in Rhesus Monkeys". NIDA Research Monograph 27: 106–113. PMID 121326. 
  11. ^ Nakamura, H.; Ishii, K.; Yokoyama, Y. et al. (November 1982). "[Physical Dependence on Loperamide Hydrochloride in Mice and Rats]". Yakugaku Zasshi (in Japanese) 102 (11): 1074–1085. PMID 6892112. 
  12. ^ "Imodium (Loperamide Hydrochloride) Capsule". DailyMed. NIH. 
  13. ^ "E-DRUG: Chlormezanone". Essentialdrugs.org. 
  14. ^ a b Butler, T. (October 2008). "Loperamide for the Treatment of Traveler's Diarrhea: Broad or Narrow Usefulness?". Clinical Infectious Diseases 47 (8): 1015–1016. doi:10.1086/591704. PMID 18781871. 
  15. ^ http://www.drugs.com/pro/loperamide.html
  16. ^ http://www.peteducation.com/article.cfm?c=0+1303+1459&aid=1432
  17. ^ http://www.nhs.uk/medicine-guides/pages/MedicineOverview.aspx?condition=Diarrhoea&medicine=imodium
  18. ^ Diarrhea During Pregnancy from PregMed.org. September 19th 2013
  19. ^ "rxlist.com". 2005. 
  20. ^ a b Bichner, F., ed. (2010). Australian Medicine Handbook. Adelaide: Australian Medicine Handbook Pty Ltd. 
  21. ^ Litovitz, T.; Clancy, C.; Korberly, B.; Temple, A. R.; Mann, K. V. (1997). "Surveillance of loperamide ingestions: An analysis of 216 poison center reports". Journal of toxicology. Clinical toxicology 35 (1): 11–19. doi:10.3109/15563659709001159. PMID 9022646.  edit

External links[edit]