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Autonomic nervous system pharma..

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Autonomic nervous system pharma..

  1. 1. AUTONOMIC NERVOUS SYSTEM Saddam Ansari Tbilisi State Medical University
  2. 2. PHARMACOLOGY OF ANS
  3. 3. Objectives Sympathomimetic drugs (drugs that act on adrenergic effector organs ) • Drugs that cause release of norepinephrine from nerve endings • Drugs that block adrenergic activity Drugs that act on cholinergic effector organs • Parasympathomimetic drugs
  4. 4. Continued… • Drugs that have a parasympathetic potentiating effect – Anticholinesterase drugs • Drugs that block cholinergic activity at effector organ – Antimuscarinic drugs Drugs that stimulate or block sympathetic and parasympathetic postganglionic neurons • Drugs that stimulate autonomic postganglionic neurons • Ganglionic blocking drugs
  5. 5. Sympathomimetic Drugs Drugs that acts like sympathetic stimulation Causes same effect There are many drugs • E.g. norepinephrine, epinephrine, methoxamine These drugs differs from one another with respect to • Degree to which they stimulate different sympathetic effector organs • Duration of action
  6. 6. Continued… • Epinephrine and norepinephrine have actions only 1 to 2 minutes • Whereas the actions of other commonly used sympathomimetic drugs lasts for approximately 30 minutes to 2 hours
  7. 7. Continued… Important drugs that stimulate specific adrenergic receptors are • Phenylephrine – alpha receptors • Isoproterenol – beta receptors • Albuterol – only beta2 receptors
  8. 8. Drugs That Cause Release of Norepinephrine Indirect sympathomimetic action These drugs include • Ephedrine • Tyramine • Amphetamine These drugs releases norepinephrine from its storage vesicles in the sympathetic nerve endings.
  9. 9. Drugs That Block Adrenergic Activity • Synthesis and storage of norepinephrine in the sympathetic nerve endings can be prevented. Best known drug is RESERPINE • Release of norepinephrine from the sympathetic endings can be blocked by GUANETHIDINE • Sympathetic alpha receptors can be blocked by PHENOXYBENZAMINE and PHENTOLAMINE
  10. 10. Continued… • The sympathetic beta receptors can be blocked. Drug that blocks all beta receptors is PROPRANOLOL and METAPROLOL blocks only beta1 receptors • Sympathetic activity can be blocked by drugs that block transmission of nerve impulses through autonomic ganglia. E.g. HEXAMETHONIUM
  11. 11. Parasympathomimetic Drugs Also known as Cholinergic Drugs These drugs are not rapidly destroyed by cholinesterase Drugs • Pilocarpine • Methacholine Act directly on muscarinic receptors
  12. 12. Continued… Also act on the effector organs of cholinergic sympathetic fibers and causes: • Profuse sweating • Vascular dilatation
  13. 13. Anticholinesterase Drugs It has parasympathetic potentiating effect Drugs: • Neostigmine • Pyridostigmine • Ambenonium
  14. 14. Antimuscarinic Drugs Blocks cholinergic activity at effector organs Drugs: • Atropine • Homatropine • Scopolamine Doesn’t effect on nicotinic action
  15. 15. DRUGS THAT STIMULATE OR BLOCK SYMPATHETIC AND PARASYMPATHETIC POSTGANGLIONIC NEURONS
  16. 16. Stimulation of Autonomic Postganglionic Neurons • Acetylcholine (injected) can stimulates postganglionic neurons of both systems • Causes sympathetic and parasympathetic effect simultaneously • Nicotine has also causes same effect
  17. 17. Ganglionic Blocking Drugs Blocks impulse transmission from the preganglionic neurons to the postganglionic neurons Drugs: • Tetraethyl ammonium ion • Hexamethonium ion • Pentolinium These drug’s effects are difficult to control –not very useful clinically

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