Benzatropine

Benzatropine (INN), also known as benztropine (USAN, BAN), is an anticholinergic marketed under the trade name Cogentin which is used in the treatment of Parkinson's disease, parkinsonism, akathisia, and dystonia.

Indications
Benzatropine is used in patients to reduce the side effects of antipsychotic treatment, such as parkinsonism and akathisia. Benzatropine is also a second-line drug for the treatment of Parkinson's disease. It improves tremor and rigidity but not bradykinesia. Benzatropine is also sometimes used for the treatment of dystonia, a rare disorder that causes abnormal muscle contraction, resulting in twisting postures of limbs, trunk, or face.

Side effects
These are principally anticholinergic:


 * Dry mouth
 * Blurred vision
 * DDS (pruritic quality is refractory to pharmacologic intervention with topical ointments and moisturizers)
 * Cognitive changes
 * Constipation
 * Urinary retention
 * Tachycardia
 * Anorexia
 * Psychosis (in overdose)

While some studies suggest that use of anticholinergics increases the risk of tardive dyskinesia (a long-term side effect of antipsychotics), other studies have found no association between anticholinergic exposure and risk of developing tardive dyskinesia, although symptoms may be worsened.

Pharmacology
Benzatropine is a centrally acting anticholinergic/antihistamine agent resulting from the combination of the tropine portion of the atropine molecule and the benzohydryl portion of diphenhydramine. Animal studies have indicated that anticholinergic activity of benzatropine is approximately one-half that of atropine, while its antihistamine activity approaches that of mepyramine. Its anticholinergic effects have been established as therapeutically significant in the management of parkinsonism. Benzatropine antagonises the effect of acetylcholine, decreasing the imbalance between the neurotransmitters acetylcholine and dopamine, which may improve the symptoms of early Parkinson's disease.

Chemistry
Benztropine, 3-(diphenylmethoxy)tropane, is synthesized by the reaction of tropine and diphenyldiazomethane.
 * R.F. Phillips, N.J. Westfield, (1952).