How anticholinergic drugs are used to treat Parkinson's disease

							How anticholinergic drugs are used to treat Parkinson's disease

The anticholinergic drugs block muscarinic receptors in the basal ganglia. to restore the
dopaminergic-to-cholinergic transmission balance. thus alleviating Parkinsons disease.
They are less effective than dopamine-increasing drugs. Anticholinergics may, however,
be used alone in the early stages of the disease. Leyodopa may then be added as
degeneration progresses. followed by the further addition of carbidopa or benzerazide.
In some countries, carbidopa and benzerazide are not available separately, but are
included in levodopa preparations.

The side-effects and problems of anticholinergic agents have been discussed in the
ANS section devoted to these drugs. It should be noted that the side-effect of dry
mouth is beneficial in Parkinsonis patients as excessive salivation is usually a problem.
These drugs include: biperiden (Akineton), orphenadrine (Disipal Orpadrex) (this also
has antihistaminic and muscle relaxing properties) trihexyphenydyl Artane.

Deprenyl

A recent approach to the treatment of Parkinson’s disease is to achieve raised CNS
dopamine levels by preventing its breakdown by MAO. Deprenyl achieves this. A great
advantage is the fact that deprenyl selectively inhibits MAO-B which is abundant in the
CNS and not MAO-A which is abundant in the gastro-intestinal tract. Tyramine which
may be contained in foodstuffs is thus still adequately broken down by MAO-A and does
not release large quantities of noradrenaline to cause a hypertensive CTISIS.

The benzodiazepines appear to cause most of their effects by potentiating the inhibitory
CNS neurotransmitter, gamma-amino-butyric acid (GABA), which leads to a decrease in
noradrenaline release.

Meprobamate

Meprobamate is very closely related to the benzodiazepines in pharmacological actions.

It is sold as a minor tranquillizers and is included in many analgesic prepaarations for its
relaxing effect. lt is possibly falling into disuse in the USA because of its addictive
properties.

Antihistamines

Many antihistamines are sedative, two which are mentioned above are speciticalb
listed in MIMS as CNS depressants. Although they are very similar to one another.

Aterax scheduled S5 whilst lndunox is S2 possibly because Aterax is registered tor
use as an anxiolytic wmlst lndunox is registered for use as an antihistamine.
Diphenhydramine, proinethazine, trimeprazine and other antihistamines are also used
as tranquillizers, premedication before surgery and hypnotics, apart from their use in
These drugs, unlike the neuromuscular blockers cause a CNS action which leads to
reduced skeletal muscle tone without acting on the muscles themselves. In normally
used dose,. they do not cause great a degree of paralysis as do the neuromuscular
blockers.

Dantrolene is a muscle relaxant that does act directly on skeletal muscles, but causes a
degree of relaxation which is more similar to that caused by centrally acting drugs than
the neuromuscular blockers.