Loperamide

Loperamide
Clinical data
Pronunciation/loʊˈpɛrəmaɪd/
Trade namesImodium, others
Other namesR-18553, Loperamide hydrochloride (USAN US)
AHFS/Drugs.comMonograph
MedlinePlusa682280
License data
Pregnancy
category
  • AU: B3
Routes of
administration		By mouth
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability<1%
Protein binding~95-97%
MetabolismLiver (extensive)
MetabolitesN-Desmethyloperamide, Loperamide-N-oxide, Loperamide carbinolamide metabolite
Onset of action~1 hour
Elimination half-life9–14 hours
Duration of actionUp to 3 days
ExcretionFeces (30–40%), urine (1%)
Identifiers
  • 4-[4-(4-Chlorophenyl)-4-hydroxypiperidin-1-yl]-N,N-dimethyl-2,2-diphenylbutanamide
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.053.088 Edit this at Wikidata
Chemical and physical data
FormulaC29H33ClN2O2
Molar mass477.05 g·mol−1
3D model (JSmol)
Solubility in waterThe water solubility of loperamide is approximately 0.14 g/100 mL at room temperature.CID Loperamide from PubChem
  • ClC1=CC=C(C2(CCN(CC2)CCC(C3=CC=CC=C3)(C(N(C)C)=O)C4=CC=CC=C4)O)C=C1
  • InChI=1S/C29H33ClN2O2/c1-31(2)27(33)29(24-9-5-3-6-10-24,25-11-7-4-8-12-25)19-22-32-20-17-28(34,18-21-32)23-13-15-26(30)16-14-23/h3-16,34H,17-22H2,1-2H3
  • Key:RDOIQAHITMMDAJ-UHFFFAOYSA-N

Loperamide hydrochloride (Brand nameː Imodium) is a man-made (synthetic) drug that treats diarrhoea and irritable bowel syndrome (IBS). It is taken orally, as tablets or capsules, liquid suspension (1mg/7.5mL) and also comes in formations that melt on the tongue. The tablets are 2mg each. It is available OTC (over the counter) in most countries including the UK and USA.

The drug is taken to treat diarrhoea short-term but can be used long-term to treat symptoms of some bowel conditions, in Crohn's disease, ulcerative colitis, and short bowel syndrome, for example. It is also given to patients after some types of surgery, for example it is used in high doses after a colonoscopy to make the bowel movements (poo) less runny. Imodium is also indicated for treating high amounts of fecal discharge in ileostomies. It reduces symptoms normally around 1 hour after taking it.

Side effects

Loperamide does not treat underlying causes. This means it only treats symptoms, but does not make what is causing diarrhoea go away, if there is an underlying cause. There may be side-effects from the underlying cause not related to the medicine, but using loperamide can causeː

When it is used with children, the drug has many different effects, or a high range of results or side effects, and is not safe to use in children. People with AIDS treated with loperamide for diarrhea may see abdominal distension and should stop therapy if this happens.

Serious side effects

Serious side effects from loperamide are rare. If there is an allergic reaction to the drug there may be swelling, redness, gasping for air (or trouble breathing), skin turning grey, blue or purple, dizziness, drowsiness, clamminess, confusion or fainting, can be an allergic or adverse reaction. If this happens it is a medical emergency, like other serious side effects.

There may be other side effects of the drug or brand, which should be listed on the leaflet inside the packet. Other, non-allergic serious side effects include

Structure

The IUPAC name for loperamide is 4-(p-chlorophenyl)-4-hydroxy-N, N-dimethyla, a-diphenyl-1-piperidinebutyramide, and can be attached to a monohydrochloride (one hydro-chloride) salt or base.

Loperamide can be sold as a combination medication, under the brand name simeticone, to treat flatulence (farting). When it is in this form it is combined with a soap to treat two symptoms at once. As simethicone its structure has a silicon dioxide attached, which is not physiologically active.

References

  1. ↑ "Loperamide (International database)". Drugs.com. 5 October 2025. Retrieved 11 October 2025.
  2. ↑ Anvisa (31 March 2023). "RDC Nº 784 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial" [Collegiate Board Resolution No. 784 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese). Diário Oficial da União (published 4 April 2023). Archived from the original on 3 August 2023. Retrieved 16 August 2023.
  3. ↑ "Imodium A-D- loperamide hydrochloride solution". DailyMed. 23 September 2025. Retrieved 11 October 2025.
  4. ↑ "Loperamide Hydrochloride capsule". DailyMed. 30 September 2022. Retrieved 11 October 2025.
  5. ↑ https://go.drugbank.com/drugs/DB00836#:~:text=The%20drug%20bioavailability%20is%20less%20than%201%25
  6. ↑ https://go.drugbank.com/drugs/DB00836#:~:text=Based%20on%20literature%20information%2C%20the%20plasma%20protein%20binding%20of%20loperamide%20is%20about%2095%25.8
  7. ↑ https://go.drugbank.com/drugs/DB00836#:~:text=8-,Metabolism,Loperamide%20carbinolamide%20metabolite,-Route
  8. ↑ https://go.drugbank.com/drugs/DB00836#:~:text=The%20onset%20of%20action%20is%20about%20one%20hour%20and%20the%20duration%20of%20action%20can%20be%20up%20to%20three%20days
  9. ↑ "Loperamide Hydrochloride". The American Society of Health-System Pharmacists. Archived from the original on 7 September 2015. Retrieved 25 August 2015.
  10. ↑ https://go.drugbank.com/drugs/DB00836#:~:text=duration%20of%20action%20can%20be%20up%20to%20three%20days
  11. 1 2 3 4 5 6 7 8 9 "IMODIUM® (loperamide hydrochloride), 4-(p-chlorophenyl)-4-hydroxy-N, N-dimethyla, a-diphenyl-1-piperidinebutyramide monohydrochloride" (PDF). FDA.gov.
  12. 1 2 3 4 5 6 7 "Loperamide: a medicine used to treat diarrhoea". nhs.uk. 2024-04-11. Retrieved 2026-04-01.
  13. 1 2 3 "Loperamide (Imodium A-D): Uses, Side Effects, Interactions, Pictures, Warnings & Dosing - WebMD". www.webmd.com. Retrieved 2026-04-01.