Blood‐brain barrier to carbidopa (MK‐486) and Ro 4–4602, peripheral dopa decarboxylase inhibitors

Treatment with L-dopa is reported to produce psychotomimetic side-effects (Jenkins & Schweiger, 1971). In schizophrenia, the high dopamine levels in the extrapyramidal system could produce sufficiently high levels of DMPEA for hallucigenic activity and at the same time antagonize the akinetic effects as seen in animal studies (Ernst, 1965). This is supported by the fact that neuroleptic drugs used in the treatment of schizophrenia, effectively reduce dopamine levels by increasing its turnover rate and are well known to produce a parkinsonian syndrome as a side-effect (Ayd, 1961).