Review of Pharmacology - 9E (2015)

Review of Pharmacology
Autonomic Nervous System
Oximes should not be given in
carbamate poisoning.
• Except ecothiophate these are not used therapeutically. Ecothiophate is useful in glaucoma.
• Other drugs are used as insecticides and are important due to their potential to cause
poisoning.
• Symptoms of anti-cholinesterase poisoning are simply the extension of the
pharmacological actions of ACh and are manifested as pin-point pupil, salivation,
lacrimation, sweating, bronchoconstriction, diarrhea, urination, bradycardia, hypotension
and coma. Blood pressure and heart rate may increase rarely due to stimulation of
nicotinic receptors.
• Atropine is an antidote of choice for both organophosphate and carbamate poisoning.
• Enzyme reactivators like pralidoxime, obidoxime and diacetylmonoxime can be used
to regenerate AChE in the organophosphate poisoning but are contra-indicated in
the carbamate poisoning. Principle indications of oximes are muscle weakness and
respiratory depression.The site on which oximes bind and reactivate the enzyme
(anionic site) is occupied by carbamates whereas it is free in the organophosphate
poisoning. (organophosphates binds to esteritic site only whereas carbamates bind
to both esteritic as well as anionic sites) Further oximes themselves possess weak AChE
inhibitory action. Due to these two reasons, oximes should not be given in carbamate
poisoning.
• Diacetylmonoxime can cross BBB and regenerate AChE in the brain whereas
pralidoxime and obidoxime cannot cross BBB.
• Chronic exposure to certain organophosphates e.g. triorthocresyl phosphate
(additive in lubricating oils) may cause:
––
Delayed neuropathy (appear 1-2 weeks after exposure) associated with
demyelination of axons. It is not caused by cholinesterase inhibition but rather
by NTE (neuropathy target esterase) inhibition.
––
Intermediate syndrome (occurs after 1-4 days) caused by cholinesterase inhibition.
60
Glaucoma
• Glaucoma is characterized by progressive damage to optic nerve associated with
raised intraocular pressure (> 21 mm Hg). Rise in intraocular tension is either due
to excessive production or due to less drainage of aqueous humor. So, the drugs
https://kat.cr/user/Blink99/