Loperamide hydrochloride (Imodium)

Loperamide hydrochloride (Imodium) is an anti-diarrhoea drug. It works by inhibiting the activity of the muscles in the gut wall, increasing the time that substances remain in the gut and allowing more water to be removed.

Loperamide is available without prescription in the United Kingdom.

Loperamide can be useful in relieving the diarrhoea caused by anti-HIV drugs such as nelfinavir (Viracept).1 However, it should not be used if there is blood in the stool.

Although it is closely related to opioid drugs like morphine, loperamide cannot cross into the brain or spinal cord tissue. Consequently, it has no painkilling or addictive properties. Despite concerns that protease inhibitors that inhibit the activity of poly-glycoprotein could allow loperamide into the brain, studies of loperamide’s effects in patients taking ritonavir (Norvir) and ritonavir-boosted tipranavir (Aptivus) found no evidence of this.2 However, ritonavir can increase loperamide’s levels in the blood, while tipranavir has the opposite effect, reducing loperamide levels by half.3

Loperamide can also halve levels of unboosted saquinavir (Invirase) in the blood, potentially putting patients at risk of treatment failure. Saquinavir also reduces loperamide’s levels.4 These drugs should not be combined for long periods, although the impact of ritonavir boosting on this interaction is unknown.

Side-effects of loperamide include drowsiness, constipation, abdominal pain, dry mouth and tiredness.


  1. Rachlis A et al. Effectiveness of step-wise intervention plan for managing nelfinavir-associated diarrhea: a pilot study. HIV Clin Trials 6: 203-212, 2005
  2. Mukwaya G et al. Interaction of ritonavir-boosted tipranavir with loperamide does not result in loperamide-associated neurologic side effects in healthy volunteers. Antimicrob Agents Chemother 49: 4903-4910, 2005
  3. Tayrouz Y et al. Ritonavir increases loperamide plasma concentrations without evidence for P-glycoprotein involvement. Clin Pharmacol Ther 70: 405-414, 2001
  4. Mikus G et al. Reduction of saquinavir exposure by coadministration of loperamide. Clin Pharmacokinet 43: 1015-1024, 2004

Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.