Due to the antidopaminergic action of anti-psychotics that extends to the tuberoinfundibular dopaminergic pathway (which plays a major role of prolactin secretion), prolactin response is used as an index of quantitative measure of the dopamine receptor blocking activity of antipsychotics in recent research situation.
When antipsychotics are prescribed to control ´psychotic symptoms, extrapyramidal syndrome (E. P. S) as a side effect appears frequently. Then, many clinicians use anticholinergic agent(such as benztropine) in the hope of avoiding this distressing side effect. But it is generally conceived that anticholinergic agent might alter the potency of antipsychotics. So the authors aimed to clarify whether thG anticholinergic agent decrease the potency of antispsyhtotics or not, with the determination of prolactin level change.
In this study the authors used haloperidol which has no active metabolites and benztropine which is prescribed commonly to control drug induced E.P.S.. With the interval of 7 days, serum prolactin levels were measured with the method of RIA upon 20 normal young male volunteers before treatment and 30min. and 60min. after treatment. The treatment is as follow: at the 1st week 1.5mg of laloperidol, at the 2nd week 1.5mg of haloperidol with 1.Omg of benztropine, and at the 3rd week 1.0mg of benztropine was given intravenously.
The results were as follows.
1. The mean baseline serum prolactin level in normal young men was 7.832. gong/ml at the 1st week, 7.225.44ng/ml at the 2nd week and 6.503.03ng/ml at the last week.
2. At the 1st week after single injection of haloperidol, the seurm prolactin level reached up to 72.7425. 19ng/ml on 30 minutes after injection and the seurm prolactin level decreased to 63.4616.92ng/ml on 60 minutes after injection.
3. At the 2nd week after injection of haloperidol with benztropine the seurm prolactin level reached up to 70.0422.31ng/ml on 30minutes after injection. And the serum prolactin level decreased to 66.9419. 14ng /ml on 60minutes after injection.
4. At the 3rd week after single injection of benztropine, there was no active prolactin response and there was no correlated change on time.
5. As the results of analysis of variance on drug and time, drugs influenced on prolactin level singnificantly (p <0.01) and time influenced on prolactin level significantly (p < 0.01) and there was interaction between durg and time (p<0.01).
6. As the comparison between treatment means, the prolactin level on 60 minutes after single injection of haloperidol was significantly lower than the level on 60 minutes after injection of haloperidol with benztropine (p <0.05) . With these results, it was proved that single administration of benztropine had no prolactin response, but benztropine in case of combined use with haloperidol had an inhibitory effect on decreasing prolactin response.
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