Benzhexol and Side Effects with Long-acting Fluphenazine Therapy

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Abstract
Sixteen patients who had for some months been on fluphenazine enanthate injections (1-3 ml) every two or three weeks, with daily oral benzhexol (6-40 mg), were divided into two groups comparable in age, diagnostic category, and drug dose. Placebo was substituted under blind controlled conditions for benzhexol in one group, and both groups were regularly assessed by Simpson rating scale for extra-pyramidal signs, and by a 30-question symptom check list. Both assessments were found reliable. Four out of eight patients had severe reactions when off benzhexol, but symptoms such as tremor and daytime sleepiness were unaltered in all patients. The other four did not suffer adversely from withdrawal of benzhexol. Acute withdrawal is therefore unjustified, but occasional revision of dosage of anti-Parkinsonian drugs is advisable. There is no evidence that tolerance develops to any effect of a phenothiazine, but long-continued benzhexol might induce a denervation supersensitivity. It is also possible that Parkinsonian signs are dependent on affective state.