In 1967 haloperidol
was introduced to the United States
as the first therapeutic alternative to the phenothiazine
s. A related compound, droperidol
, was also introduced. Haloperidol is used primarily for its antipsychotic
effects, while droperidol is used primarily for its antinausea
Pharmacologically, haloperidol is very similar to the phenothiazines. It produces sedation and an indifference to external stimuli and reduces initiative, anxiety, and activity. It is well absorbed orally and has a moderately slow rate of metabolism and excretion. Stable blood levels can be seen for up to 3 days following discontinuation. It takes approximately 5 days for 40% of a single dose to be excreted by the kidneys.
The mechanism of the antipsychotic action of haloperidol is like that of the phenothiazines--it occupies and competitively blocks dopamine2 receptors. Haloperidol does not produce many of the serious side effects observed in patients taking phenothiazines (jaundice, blood abnormalities), but it does cause parkinsonian motor movements that are the same or greater intensity as those induced by the high-potency phenothiazines. Prophylactic antiparkinsonian medication is sometimes needed.
A Primer of Drug Action, Robert Julien