Dirty drug

A dirty drug is an informal term used in pharmacology to describe drugs that may bind to many different molecular targets or receptors in the body, and so tend to have a wide range of effects and possibly negative side effects. Today, pharmaceutical companies try to make new drugs as selective as possible to minimise binding to antitargets and hence reduce the occurrence of side effects and risk of adverse reactions.

Examples of compounds often cited as "dirty drugs" include chlorpromazine, dextromethorphan and ibogaine, all of which bind to multiple receptors or influence multiple receptor systems. There may be instances of advantages to drugs that exhibit multireceptor activity such as the antiaddictive drug ibogaine that acts within a broad range of neurohormonal systems where activity is also exhibited by drugs commonly associated with addiction including opioids, nicotine, and alcohol. Similarly chlorpromazine is primarily used as an antipsychotic, but its strong serotonin receptor blocking effects make it useful for treating serotonergic crisis such as serotonin syndrome. Dextromethorphan for its part is widely used as a cough medication, but its other actions have led to trials for several conditions such as its use as an adjunct to analgesia, and a potential anti-addictive drug, as well as its occasional recreational use as a dissociative.