Drugs Acting on Cholinergic Nerve Terminals PDF

Dr. Entisar Al-Mukhtar https://www.youtube.com/watch?v=ioOvKGR 1YlQ&t=55s https://www.youtube.com/watch?v=ioOvKGR1 YlQ&t=55s Note that the lifetime of Ach in the synaptic cleft is extremely short due t...

Dr. Entisar Al-Mukhtar https://www.youtube.com/watch?v=ioOvKGR 1YlQ&t=55s https://www.youtube.com/watch?v=ioOvKGR1 YlQ&t=55s Note that the lifetime of Ach in the synaptic cleft is extremely short due to metabolism by cholinesterase. Agents that interfere with cholinergic transmission & are of therapeutic use generally act by interaction with cholinoceptors. The only notable exception to this isthe use of cholinesterase inhibitors to decrease the rate of Ach degradation and so prolong the lifetime of Ach within the synaptic cleft. Myasthenia gravis treatment  DrugType Drug Action Nicotinic Cholinoceptor Tubocurarine, pancuronium Muscle paralysis during anaesthesia Antagonist Treatmentof Glaucoma Muscarinic GImotility after surgery. Cholinoceptor Pilocarpine Suppression of atrial tachycardia. Agonists Stimulates bladder emptying. Hyoscine butylbromide Anestheticpremedication, motion sickness ( scopolamine ) Muscarinic Ipratropium bromide Treat bronchoconstriction in asthmatics Cholinoceptor Antagonist Homatropine, Tropicamide Pupillary dilation andparalysis Diagnosis of myasthenia & to distinguish Edrophonium (short acting, given I.V ) weakness if it is due to (‘cholinergic gravis crisis’) or (‘myasthenic crisis’) Cholinesterase -Stimulate the bladder and GIT, Inhibitors - Antidote for competitive Neostigmine , pyridostigmine neuromuscular- blocking agents, - Myasthenia gravis treatment physostigimine,dyflos () Treatment of glaucoma Tacrine, Donepezil, Rivastigmine & Galantamine (are irreversible Alzheimer’s disease treatment , Tacrine  & asthma (Uptake 1 ) (Uptake 2) Indirectly-acting sympathomimetic agents (IASAs) (e.g., tyramine, amphetamine, ephedrine) t  Uptake 1 inhibitors Comprise an important class oftherapeutic agents, the tricyclic antidepressants (e.g., amitriptyline). These agents exert their therapeutic actions centrally & their possible peripheral actions (e.g. tachycardia & cardiac dysrhythmias) are unwanted side effects. Drug Type Drug Action Selective β1Agonist Dobutamine + ve inotropic/chronotropic effects. Salbutamol, Bronchodilation Selective β2 Agonist terbutaline Phenylephrine, Nasal decongestants Selective α1Agonist oxymetazoline Adrenaline Local vasoconstriction to retard the dissipation of anaesthetic Clonidine Anti-Hypertension. Act on presynaptic Selective α2 Agonist receptors to reduce NA release Phentolamine, Peripheral vasodilation. α-Antagonist phenoxybenzamine Treat peripheral vascular disease. Not used to treat hypertension as they cause postural hypotension. Selective α1Antagonist Prazosin Usedto treat hypertension β-Antagonists Propranolol, Usedto treat hypertension, MI, Angina. (Blockers) Unwanted side effects include bronchoconstriction.  Figure 7.10 Some clinical Figure 7.6 Actions of applications of β-blockers. propranolol and other β AV = atrioventricular. blockers. https://www.youtube.com/watch?v=_SpJLkY5J gA&t=3s