<P> The bioavailability of oral haloperidol ranges from 60--70% . However, there is a wide variance in reported mean T and T in different studies, ranging from 1.7 to 6.1 hours and 14.5 to 36.7 hours respectively . </P> <P> The drug is well and rapidly absorbed with a high bioavailability when injected intramuscularly . The T is 20 minutes in healthy individuals and 33.8 minutes in patients with schizophrenia . The mean T is 20.7 hours . The decanoate injectable formulation is for intramuscular administration only and is not intended to be used intravenously . The plasma concentrations of haloperidol decanoate reach a peak at about six days after the injection, falling thereafter, with an approximate half - life of three weeks . </P> <P> The bioavailability is 100% in intravenous (IV) injection, and the very rapid onset of action is seen within seconds . The T is 14.1 to 26.2 hours . The apparent volume of distribution is between 9.5 and 21.7 L / kg . The duration of action is four to six hours . If haloperidol is given as a slow IV infusion, the onset of action is slowed, and the duration of action is prolonged . </P> <P> Plasma levels of four to 25 micrograms per liter are required for therapeutic action . The determination of plasma levels can be used to calculate dose adjustments and to check compliance, particularly in long - term patients . Plasma levels in excess of the therapeutic range may lead to a higher incidence of side effects or even pose the risk of haloperidol intoxication . </P>

An advantage of the drug haldol (haloperidol) over thorazine (chlorpromazine) is that haldol