Many typical antipsychotic drugs may be manufactured as alcohols, which react with carboxylic acids to form esters (organic salts). These compounds are highly oil-soluble, but are only sparingly soluble in aqueous fluids such as blood. Thus, an oily solution of an antipsychotic can be injected into a muscle, where it forms a reservoir or ‘depot’ of drug that is slowly dissolved in the surrounding blood. Once released into the blood, drug esters are rapidly hydrolysed by endogenous esterase enzymes to produce the parent antipsychotic. Stable serum concentrations of antipsychotics are usually engendered (although this is not always observed in practice (Tuninger & Levander, 1996)), and administration need only take place every few weeks or so. Adherence can be assured and relapse rates are reduced (Groves & Mandel, 1975: Davis et al, 1994).