VPT 321: Veterinary Neuropharmacology (2+1) copy 1

THERAPEUTIC USES

Glaucoma

• Physostigmine can be administered as eye drops to cause constriction of the pupil and ciliary muscle, improving drainage of aqueous humour, thus reducing intraocular pressure.

Myasthenia gravis

• It is an auto immune disorder due to development of antibodies directed to nicotinic receptors at the muscle end plate and a reduction in the number of N_M cholineceptors.
• So weakness and easy fatigability are noticed on repeated activity.
• Neostigmine improves muscle contractions by allowing the acetylcholine released from the prejunctional endings to accumulate and act on the receptors over a large area and by directly depolarising the end plate.
• For this purpose, it is used in combination with atropine. Over treatment with anticholinesterases can produce weakness by causing persistent depolarisation of muscle end plate. This is called cholinergic weakness.
• If edrophonium is administered and there is improvement in the condition of muscle weakness, then it may be due to myasthenia gravis or if the condition worsens, it may be due to anticholinesterase over treatment.

Post operative paralytic ileus and atony of the rumen

Post operative decurarization

• Atropine poisoning – Physostigmine can be used. Since it crosses the blood brain barrier, it is especially used to treat CNS effects.
• Cobra bite – Neostigmine with atropine is used to prevent respiratory paralysis.
• Alzhemier’s disease – Tacrine is administered.