Talk:Positive allosteric modulator
A positive allosteric modulator (PAM) is a molecule that binds to a receptor and enhances the efficacy of the natural agonist.
Positive allosteric modulators cannot be competitive to the endogenous ligand: that is to say that any PAM must bind to a distinctly different site on a cell than the agonist. 
There are many drugs that are positive allosteric modulators. Benzodiazepines (such as diazepam), along with alcohol and barbiturates (such as phenobarbital) enhance GABA. As GABA is the main inhibitory neurotransmitter in the brain, increasing its efficiency causes effects such as anxiolysis, sedation and skeletal muscle relaxation . Some cannabinoids also appear to be PAMs (CBD is a PAM at two opioid receptors). This modulation may account for reported analgesia in cancer patients using CBD oil.