A double-blind, randomized, placebo controlled, partial 4-way crossover interaction study to examine the effects of a single dose of haloperidol or placebo on THC-induced CNS effects in healthy male volunteers

As there is a large amount of evidence for the relation between cannabis and
psychosis and the possible increase of forebrain dopamine by THC, THC-induced
psychotomimetic effects could be used as a practical *psychosis*-model, to
assess therapeutic effects of (novel) antipsychotic agents.

The current study is designed as a first exploration of this model. The
hypothesis is that haloperidol will lead to an amelioration of the
*psychotomimetic* effects of the THC-challenge.

This will be a double-blind, randomized, placebo controlled, partial 4-way
crossover interaction study in healthy volunteers.

The two drugs used in the study are haloperidol 3 mg orally administrated and
THC intrapulmonary (2, 4, 6 mg with intervals of 90 minutes) or the placebos of
both drugs.

Side-effects haloperidol:
- expected: sleepiness, lightheadedness (upon standing), dizziness: these
effects usually disappear within a couple of hours.
- rare: dystonia: for this rare side-effect there will be biperideen
(Akineton®). The effect of biperideen occurs rapidly, usually within 20
minutes.
Side-effects THC: some people experience the relaxing effects of THC and feel
free of troubles, whereas other people feel terrified or confused. THC is an
appetizer and causes muscle relaxation. Short memory is impaired and an
increase in heart rate is observed. Given the short period of use these side
effects are expected to be mild and expected to last for only a couple of hours
after the last inhalation. People who are sensitive to the effects of marijuana
can develop a psychosis in the short term. That*s why people with a history of
psychosis cannot participate in this study.