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Research · Medication

Loperamide

Trials found loperamide shortened acute diarrhea in adults and in children, and added to antibiotics it raised cure at 24 hours in travelers' diarrhea. Constipation was its most common side effect. FDA states that doses far above the label caused abnormal heart rhythms, cardiac arrest and deaths, mostly in misuse, and serious reactions in children occurred only under age 3.

Add to Bio HackChecked 2026-11-14
Status
Loperamide 2 mg is sold over the counter in the US (Imodium A-D and store brands) to control symptoms of diarrhea, including travelers' diarrhea, at no more than 8 mg a day for adults. Prescription loperamide capsules are FDA-approved for acute nonspecific diarrhea from age 2, chronic diarrhea in adults with inflammatory bowel disease, and reducing ileostomy output, at up to 16 mg a day. The prescription label carries a boxed warning about Torsades de Pointes and sudden death at doses above the label.
Also called
loperamide hydrochloride, Imodium, Imodium A-D, Imodium Multi-Symptom Relief, loperamide and simethicone, anti-diarrheal, antidiarrheal
Taken for
diarrhea, traveler's diarrhea, stomach bug, IBS with diarrhea, chronic diarrhea, fecal incontinence, ileostomy output, opioid withdrawal

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

Reported risks7

What people take it for, and what was found

Shown to help4

Limited

Acute diarrhea in adults

One trial found loperamide cut the median time to the last unformed stool to 11.5 hours, against 29.4 hours on placebo, in adults with acute diarrhea.

Compared with placebo [1]; racecadotril, an antidiarrheal not sold in the US [2]

The numbers and sources
Effect
Over 48 hours, the median time to the last unformed stool was 11.5 hours on loperamide 2 mg tablets, 29.4 hours on placebo, 26.0 hours on simethicone alone and 7.6 hours on loperamide with simethicone [1]. Against racecadotril, pooled clinical response did not differ (OR 0.80, 95% CI 0.47 to 1.37, 3 trials) [2].
Population
483 adults with acute nonspecific diarrhea and gas-related abdominal discomfort, in a 4-arm randomized trial [1]; 5 randomized trials in adults with acute watery diarrhea of presumed infectious origin, 3 pooled for clinical response [2].
Sources
[1], [2]
Caveats
The medians use the trial's alternate definition of an episode, and the abstract gives no confidence interval for loperamide alone against placebo [1]. The racecadotril review's abstract states a benefit for racecadotril that its own pooled clinical response result does not show [2].
Moderate

Travelers' diarrhea, added to antibiotics

Shown to raise clinical cure at 24 hours in travelers' diarrhea when added to antibiotics, odds ratio 2.6 against antibiotics alone.

Compared with the same antibiotics alone [3]; bismuth subsalicylate [4]

The numbers and sources
Effect
In 6 paired studies, antibiotics with loperamide raised the odds of clinical cure at 24 hours (OR 2.6, 95% CI 1.8 to 3.6) and at 48 hours (OR 2.2, 95% CI 1.5 to 3.1) against antibiotics alone, with no evidence of heterogeneity [3]. In a head-to-head trial, people on loperamide passed fewer unformed stools than people on bismuth subsalicylate in every period through 48 hours, and illness was not prolonged in shigellosis [4]. An expert panel's graded review concluded that fluids alone, loperamide or bismuth subsalicylate may suffice for most mild travelers' diarrhea [5].
Population
9 studies with 12 loperamide and antibiotic regimens in adults [3]; 219 students traveling in 7 Latin American countries [4]; an expert panel's appraisal of the literature [5].
Sources
[3], [4], [5]
Caveats
The pooled benefit is for loperamide on top of antibiotics. [5] is a guideline built on critical appraisal and panel votes, not a pooled analysis.
ModerateStudied in children

Acute diarrhea in children

Shown to shorten acute diarrhea in children under 12 by about 0.8 days against placebo. Serious reactions occurred only in children under 3.

Compared with placebo [6]

The numbers and sources
Effect
Against placebo, fewer children still had diarrhea at 24 hours (prevalence ratio 0.66, 95% CI 0.57 to 0.78), diarrhea lasted 0.8 days less (95% CI 0.7 to 0.9), and stool counts at 24 hours were lower (ratio 0.84, 95% CI 0.77 to 0.92) [6].
Population
Randomized placebo-controlled trials in children younger than 12 with acute diarrhea, 927 on loperamide and 764 on placebo [6].
Sources
[6]
Caveats
Serious adverse events appear under Risks. The authors found that in children under 3, malnourished, dehydrated, systemically ill or with bloody diarrhea, harms outweighed benefits [6]. The US prescription label contraindicates it under age 2 [7].
Limited

IBS with diarrhea

One small trial found firmer stools, fewer bowel movements and less pain on loperamide than placebo in IBS, with more pain at night. Guideline reviewers rated the evidence very low.

Compared with placebo [8]

The numbers and sources
Effect
Over 5 weeks, the loperamide group had improved stool consistency (32%), fewer bowel movements (36%) and lower pain intensity (30%), and more pain at night [8]. An American Gastroenterological Association evidence review gave loperamide for IBS with diarrhea a conditional rating on very low certainty evidence [9].
Population
90 adults with IBS in a 5-week double-blind trial, 35 on loperamide and 34 on placebo analyzed, 21 dropouts [8]; a guideline panel's evidence review [9].
Sources
[8], [9]
Caveats
The trial enrolled an unselected IBS group, not only people with diarrhea, and lost nearly a quarter of its participants [8].

Mixed results1

Limited

Fecal incontinence

Limited evidence: small trials found less leakage in people with loose stools, while a 300-woman trial found no difference from placebo at 24 weeks.

Compared with placebo [10][11]; psyllium fiber [12]

The numbers and sources
Effect
A Cochrane review of 16 small trials found limited evidence that antidiarrheal drugs may reduce fecal incontinence in people with liquid stools, with more adverse effects on loperamide than placebo, and no data suitable for meta-analysis [10]. In women with fecal incontinence and normal stool consistency, the change in severity score at 24 weeks did not differ between loperamide and placebo (-1.5 points, 95% CI -3.4 to 0.4) [11]. In a 4-week crossover trial, loperamide and psyllium did not differ in incontinence episodes, and both lowered episodes from baseline [12].
Population
558 participants in 16 trials [10]; 300 women randomized at 8 US sites [11]; 80 community-dwelling adults, 68% men [12].
Sources
[10], [11], [12]
Caveats
The Cochrane trials were small and short, most of them in people with chronic diarrhea [10]. The large trial enrolled women with normal stool consistency [11].

Claimed, not studied in people1

Untested

Easing opioid withdrawal

Not studied in people. People report taking very high doses to ease opioid withdrawal, and in monkeys high doses prevented morphine withdrawal signs.

No study in people. This rests on animal studies, what users report.

The numbers and sources
Effect
In morphine-dependent monkeys, loperamide at doses above human doses prevented signs of morphine withdrawal, and the label states that loperamide is mainly misused to relieve opioid withdrawal [7]. Of 22 abuse cases reported to FDA, 9 involved use to prevent withdrawal, at a median 250 mg a day [13]. Poison center reviews tied a rise in misuse to online instructions, and Google searches for "loperamide withdrawal" rose from 2011 [14].
Population
Morphine-dependent monkeys [7]; spontaneous reports to FDA [13]; poison center calls and internet search trends [14].
Sources
[7], [13], [14]
Caveats
No trial in people tested it. The doses reported for this use are the doses linked to the heart rhythm deaths under Risks.

Doses studied

The over-the-counter label directs adults and children 12 and over to take 4 mg after the first loose stool and 2 mg after each later one, with no more than 8 mg in 24 hours, and lower limits for children 6 to 11 [15]. The prescription label uses the same starting doses with a maximum of 16 mg a day, and the average maintenance dose in chronic diarrhea trials was 4 to 8 mg a day [7]. The acute diarrhea trial used 4 mg then 2 mg after each unformed stool, up to 8 mg in 24 hours, for 48 hours [1]. The fecal incontinence trial in women started at 2 mg a day with dose changes allowed [11]. The children's trials pooled in [6] were judged at doses of 0.25 mg/kg a day or less.

Risks

Reported risks6

ModerateCommon

Constipation

Shown to raise constipation, 2.6% against 0.8% on placebo in acute diarrhea trials and 5.3% against none in chronic diarrhea trials.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
In 4 placebo-controlled acute diarrhea trials, constipation occurred in 2.6% on loperamide and 0.8% on placebo. In 20 placebo-controlled chronic diarrhea trials, it occurred in 5.3% and 0.0%, and dizziness in 1.4% and 0.7% [7]. Against psyllium in fecal incontinence, constipation occurred in 29% on loperamide and 10% on psyllium [12]. Against racecadotril, pooled odds of constipation were lower on racecadotril (OR 0.21, 95% CI 0.13 to 0.33, 4 trials) [2].
Population
467 patients in acute and 562 in chronic diarrhea trials [7]; 80 adults with fecal incontinence [12]; adults with acute infectious diarrhea [2].
Sources
[7], [12], [2]
Caveats
The label notes that many reported effects are also symptoms of the diarrhea itself [7].
ModerateStudied in childrenUncommon

Serious reactions in young children

Shown in pooled trials to cause serious reactions, ileus, lethargy or death, in 0.9% of children on loperamide against none on placebo, all under age 3.

The numbers and sources
How common
Uncommon: between 1 in 1,000 and 1 in 100 people.
Effect
Serious adverse events occurred in 8 of 927 children on loperamide (0.9%, 95% CI 0.4% to 1.7%) and none of 764 on placebo, all in children younger than 3 [6]. The label contraindicates loperamide under age 2 because of respiratory depression and serious cardiac reactions, and lists postmarketing cardiac arrest, syncope and respiratory depression in that age group [7].
Population
Children under 12 in randomized trials [6]; postmarketing reports [7].
Sources
[6], [7]
Caveats
The over-the-counter label directs parents of children 2 to 5 to ask a doctor [15].
LimitedHow often is not known

FDA boxed warning: Torsades de Pointes and sudden death

FDA states that doses far above the label caused abnormal heart rhythms, cardiac arrest and deaths, mostly in people misusing it. The prescription label carries a boxed warning.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The label's boxed warning states that Torsades de Pointes, cardiac arrest and death have been reported at higher than labeled doses. Overdose cases at 70 to 1,600 mg a day, 4 to 100 times the labeled dose, included QT and QRS prolongation, Brugada syndrome, ventricular arrhythmias and death. Syncope and ventricular tachycardia were also reported at the labeled dose in people taking other drugs or with other risk factors [7]. FDA reported in 2018 that it continued to receive reports of serious heart problems and deaths, primarily in intentional misuse, and worked with manufacturers on blister packs and smaller packages [16]. FDA's own review of reports through 2015 found 48 serious cardiac cases, including 24 with syncope, 13 with cardiac arrest, 7 with Torsades de Pointes and 10 deaths, at a median 250 mg a day in abuse cases [13]. A review of 129 published cases found a median dose of 200 mg a day, severe toxicity in 64% and death in 13%. Severity rose with dose (adjusted OR 1.04 per 10 mg, 95% CI 1.01 to 1.07), and severe toxicity occurred at doses as low as 20 to 40 mg a day [17].
Population
Postmarketing and published cases [7][13][17]; FDA's 2018 update [16].
Sources
[7], [16], [13], [17]
Caveats
Case reports cannot give a rate. Many cases involved other drugs taken to raise loperamide levels [16][17].
LimitedHow often is not known

Misuse and abuse

Case series: US poison centers logged 12,987 loperamide cases from 2010 to 2022, with 59 deaths, and reports fell after FDA warnings and packaging limits.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Of 12,987 cases, 13.4% had a serious medical outcome and 59 died (0.5%). Serious outcomes were most often tied to abuse (38.0%), suspected suicide (27.5%) or intentional misuse (15.7%). Cases per 100,000 people rose to 0.46 in 2017 and fell to 0.28 in 2022 [18]. In an abuse potential study of 9 people who had used opiates, 44% felt a single 60 mg dose. The label states misuse occurs especially at 60 mg or more, and that injected loperamide caused physical dependence in animals [7].
Population
Cases reported to US poison centers [18]; 9 experienced opiate users in a crossover study and animal dependence studies [7].
Sources
[18], [7]
Caveats
Poison center data count calls, not all users, and cannot prove the FDA actions caused the fall [18].
LimitedHow often is not known

Ileus, toxic megacolon and dysentery

The label warns of ileus and toxic megacolon and contraindicates use in dysentery with bloody stool and fever, acute ulcerative colitis, and invasive bacterial enterocolitis.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The label warns against use when slowing the gut is to be avoided, because of ileus, megacolon and toxic megacolon, and reports isolated toxic megacolon in people with AIDS and infectious colitis. It contraindicates use in acute dysentery, acute ulcerative colitis and enterocolitis from Salmonella, Shigella or Campylobacter, and in abdominal pain without diarrhea [7]. The over-the-counter label says not to use it with bloody or black stool [15].
Population
Postmarketing reports and label statements [7][15].
Sources
[7], [15]
Caveats
Label statements built from case reports, with no rate given.
LimitedHow often is not known

Drug interactions

The label warns that itraconazole, gemfibrozil, quinidine and ritonavir raise loperamide levels, up to 12.6-fold for two combined, and that QT-prolonging drugs add heart rhythm risk.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Itraconazole raised peak loperamide levels 2.9-fold and exposure 3.8-fold. Gemfibrozil raised them 1.6-fold and 2.2-fold, and the two together 4.2-fold and 12.6-fold. Quinidine or ritonavir raised loperamide levels 2- to 3-fold. The label warns against combining loperamide with QT-prolonging drugs, naming antiarrhythmics, antipsychotics, moxifloxacin, pentamidine and methadone [7]. The over-the-counter label tells people taking a prescription drug to ask a doctor or pharmacist first [15].
Population
Drug level studies in volunteers given single 4 mg or 16 mg doses [7].
Sources
[7], [15]
Caveats
Drug level studies, not outcome trials. In abuse cases, people took cimetidine and other drugs on purpose to raise loperamide levels [17].

Mixed results1

LimitedStudied in pregnancyHow often is not known

Use in pregnancy and breastfeeding

Limited evidence: one registry linked early-pregnancy use to slightly more malformations, mainly hypospadias, while a 105-woman cohort found no rise in major malformations.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In the Swedish birth register, early-pregnancy use was linked to any congenital malformation (OR 1.43, 95% CI 1.04 to 1.96, 43 cases) and hypospadias (RR 3.2, 95% CI 1.3 to 6.6, 7 cases) [19]. In a matched cohort from 5 teratogen information centers, major malformations did not differ from controls [20]. The label states small amounts appear in breast milk and that it is not advised during breastfeeding [7].
Population
Women in the Swedish Medical Birth Register who used loperamide in early pregnancy, 1995 to 2004 [19]; 105 pregnant women, 89 exposed in the first trimester, and matched controls [20].
Sources
[19], [20], [7]
Caveats
Observational studies with few cases. The registry authors called for confirmation in other large studies [19].

Claims tested and not found

  1. That loperamide prolongs travelers' diarrhea caused by Shigella. In a trial against bismuth subsalicylate, illness was not significantly prolonged in people with shigellosis on loperamide [4].
  2. That loperamide reduces fecal incontinence in women with normal stools. In 300 women followed 24 weeks, severity scores did not differ between loperamide and placebo [11].

Sources

  1. Hanauer SB, DuPont HL, Cooper KM, Laudadio C. 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. Current Medical Research and Opinion. 2007. https://doi.org/10.1185/030079907x182176
  2. Aziz M, Malik LU, Javed E, et al. Racecadotril Versus Loperamide for Acute Diarrhea of Infectious Origin in Adults: A Systematic Review and Meta-Analysis. Health Science Reports. 2025. https://doi.org/10.1002/hsr2.70849
  3. Riddle MS, Arnold S, Tribble DR. Effect of adjunctive loperamide in combination with antibiotics on treatment outcomes in traveler's diarrhea: a systematic review and meta-analysis. Clinical Infectious Diseases. 2008. https://doi.org/10.1086/591703
  4. Johnson PC, Ericsson CD, DuPont HL, et al. Comparison of loperamide with bismuth subsalicylate for the treatment of acute travelers' diarrhea. JAMA. 1986. https://doi.org/10.1001/jama.1986.03370060071021
  5. Riddle MS, Connor BA, Beeching NJ, et al. Guidelines for the prevention and treatment of travelers' diarrhea: a graded expert panel report. Journal of Travel Medicine. 2017. https://doi.org/10.1093/jtm/tax026
  6. Li ST, Grossman DC, Cummings P. Loperamide therapy for acute diarrhea in children: systematic review and meta-analysis. PLoS Medicine. 2007. https://doi.org/10.1371/journal.pmed.0040098
  7. US Food and Drug Administration label. Loperamide hydrochloride capsules USP, Rx only. DailyMed. 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=580e6cd4-3f05-4996-9dc3-c50d757ae210
  8. Efskind PS, Bernklev T, Vatn MH. A double-blind placebo-controlled trial with loperamide in irritable bowel syndrome. Scandinavian Journal of Gastroenterology. 1996. https://doi.org/10.3109/00365529609006766
  9. Lembo A, Sultan S, Chang L, et al. AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Diarrhea. Gastroenterology. 2022. https://doi.org/10.1053/j.gastro.2022.04.017
  10. Omar MI, Alexander CE. Drug treatment for faecal incontinence in adults. Cochrane Database of Systematic Reviews. 2013. https://doi.org/10.1002/14651858.cd002116.pub2
  11. Jelovsek JE, Markland AD, Whitehead WE, et al. Controlling faecal incontinence in women by performing anal exercises with biofeedback or loperamide: a randomised clinical trial. The Lancet Gastroenterology & Hepatology. 2019. https://doi.org/10.1016/s2468-1253(19)30193-1
  12. Markland AD, Burgio KL, Whitehead WE, et al. Loperamide Versus Psyllium Fiber for Treatment of Fecal Incontinence: The Fecal Incontinence Prescription (Rx) Management (FIRM) Randomized Clinical Trial. Diseases of the Colon & Rectum. 2015. https://doi.org/10.1097/dcr.0000000000000442
  13. Swank KA, Wu E, Kortepeter C, McAninch J, Levin RL. Adverse event detection using the FDA post-marketing drug safety surveillance system: Cardiotoxicity associated with loperamide abuse and misuse. Journal of the American Pharmacists Association. 2017. https://doi.org/10.1016/j.japh.2016.11.011
  14. Borron SW, Watts SH, Tull J, et al. Intentional Misuse and Abuse of Loperamide: A New Look at a Drug with "Low Abuse Potential". The Journal of Emergency Medicine. 2017. https://doi.org/10.1016/j.jemermed.2017.03.018
  15. US Food and Drug Administration label. Imodium A-D (loperamide hydrochloride) tablet, Drug Facts. DailyMed. 2025. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=01da76d0-1979-4c45-9d39-c72ae4e4ffe2
  16. US Food and Drug Administration. FDA Drug Safety Communication: FDA limits packaging for anti-diarrhea medicine loperamide (Imodium) to encourage safe use. 2018. https://www.fda.gov/files/FDA-limits-packaging-for-anti-diarrhea-medicine-loperamide-(Imodium)-to-encourage-safe-use_PDF.pdf
  17. Bekka E, Martinez-De la Torre A, Haschke M, Liakoni E, Weiler S. Toxicity profile of supratherapeutic loperamide: a systematic review and dose-response analysis. Clinical Toxicology. 2026. https://doi.org/10.1080/15563650.2026.2634757
  18. Patel A, Rine NI, Spiller HA, et al. Loperamide cases reported to United States poison centers, 2010 to 2022. Injury Epidemiology. 2023. https://doi.org/10.1186/s40621-023-00473-2
  19. Källén B, Nilsson E, Otterblad Olausson P. Maternal use of loperamide in early pregnancy and delivery outcome. Acta Paediatrica. 2008. https://doi.org/10.1111/j.1651-2227.2008.00718.x
  20. Einarson A, Mastroiacovo P, Arnon J, et al. Prospective, controlled, multicentre study of loperamide in pregnancy. Canadian Journal of Gastroenterology. 2000. https://doi.org/10.1155/2000/957649

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