Procyclidine

Medical uses

It is used in patients with parkinsonism and akathisia, and to reduce the side effects of antipsychotic treatment given for schizophrenia. Procyclidine is also a second-line drug for the treatment of Parkinson's disease. It improves tremor but not rigidity or bradykinesia.

Procyclidine is also sometimes used for the treatment of dystonia (but not tardive dyskinesia), a rare disorder that causes abnormal muscle contraction, resulting in twisting postures of limbs, trunk, or face.

Side effects

Side effects include nausea, constipation, urinary retention, blurred vision, anxiety, cognitive impairment, confusion, dizziness, gingivitis, hallucination, memory loss, rash and vomiting.

Overdose

Signs of procyclidine overdose are those of an anticholinergic and include confusion, agitation and sleeplessness that can last up to or more than 24 hours. Pupils become dilated and unreactive to light. Tachycardia (fast heart beat), as well as auditory and visual hallucinations have also been reported.

Other known symptoms of overdose are: clumsiness or unsteadiness, being severely drowsy, having a severely dry mouth, nose, or throat, having an altered mood or other mental changes, seizures, being short of breath or having troubled breathing, a dry and warm, flushed skin.

A suspected overdose with severe life-threatening symptoms should immediately be brought to medical attention, where reversal can be attempted with physostigmine administered intravenously or subcutaneously.

Pharmacology

Pharmacodynamics

Procyclidine is an anticholinergic. It is specifically an antimuscarinic. The drug acts as a non-selective antagonist of the muscarinic acetylcholine M1, M2, and M4 receptors, whereas its activities at the M3 and M5 receptors are reportedly unknown.

Chemistry

Synthesis

Procyclidine, 1-cyclohexyl-1-phenyl-3-pyrrolidinopropan-1-ol, is synthesized in exactly the same manner as was seen for trihexyphenidyl, except this time the linear synthesis begins with the preparation of 3-(1-pyrrolidino)propiophenone.

In an interesting variation, the ketone is first reacted with phenylmagnesium bromide. Catalytic hydrogenation of the carbinol thus obtained can be stopped after the reduction of only one aromatic ring.

Morton method: The Reformatsky reaction between Cyclohexyl phenyl ketone (BzCy) [712-50-5] (1) and Ethyl Bromoacetate [105-36-2] (2) gives ethyl 3-cyclohexyl-3-hydroxy-3-phenylpropanoate, PC12565684 (3). The reduction of the ester gives 1-cyclohexyl-1-phenylpropane-1,3-diol, PC13841193 (4). FGI of the primary alcohol to the Tosyl leaving group gives 3-Cyclohexyl-3-hydroxy-3-phenylpropyl 4-methylbenzenesulfonate [102473-43-8] (5). Alkylation with pyrrolidine [123-75-1] completes the synthesis of procyclidine.

References

References

1. "Procyclidine Hydrochloride". National Institute for Health and Care Excellence.
2. (May 2019). "DARK Classics in Chemical Neuroscience: Atropine, Scopolamine, and Other Anticholinergic Deliriant Hallucinogens". ACS Chem Neurosci.
3. "Verfahren zur Herstellung von tertiäeren Aminoalkoholen [Process for the preparation of tertiary amino alcohols]".
4. (1951). "11. Aminoalkyl tertiary carbinols and derived products. Part IV. Spasmolytics. Phenyl- and cyclohexylphenyl-carbinols". Journal of the Chemical Society (Resumed).
5. Harfenist Morton, Ernest G Magnien, {{US patent. 2842115 (1958 to Burroughs Wellcome Co).
6. , GB773748 (1957 to Wellcome Foundation Ltd).