CHOLINOCEPTOR-BLOCKING DRUGS Flashcards
MUSCARINIC ANTAGONISTS Selective Only a few receptor-selective --- antagonists have reached clinical trial Pirenzipine
M1
MUSCARINIC ANTAGONISTS
A. CLASSIFICATION AND PHARMACOKINETICS
Subdivided into
Most of the drugs in the market
- Nonselective
Cholinoreceptor antagotists are divided into two:
- Muscarinic, blocks parasympathetic autonomic discharge. Atropine is the prototype of these drugs.
- Nicotinic, competitively block the actions of acetylcholine at nicotinic receptors of both parasympathetic and sympathetic ganglia.
MUSCARINIC
NICOTINIC
Cholinoreceptor antagotists are divided into two:
blocks parasympathetic autonomic discharge. Atropine is the prototype of these drugs.
Muscarinic
Cholinoreceptor antagotists are divided into two:
competitively block the actions of acetylcholine at nicotinic receptors of both parasympathetic and sympathetic ganglia.
Nicotinic
Prototype nonselective muscarinic
blocker
Derivative of a deadly night shade
Atropa belladona and other plants
ATROPINE
Tertiary amine Relatively lipid soluble Crosses membrane barriers Well distributed in the CNS and other organs
ATROPINE
Eliminated partially by metabolism in
the liver
Partially by renal excretion
Elimination half-life is 2 hours
ATROPINE
Duration of action of normal doses is 4-8 hours in all organs For the eye, it last for 72 hours Salivary or bronchial glands are sensitive to the effect of atropine
ATROPINE
organ affected by muscarinic antagonists
Sedation, hallucination, drowsiness, antimotion sickness action, antiparkinson action, amnesia
CNS
organ affected by muscarinic antagonists
Mydriasis, cyclopegia, lacrimal glands become dry and sandy
eye
organ affected by muscarinic antagonists
Initial bradycardia at low doses then tachycardia
heart
organ affected by muscarinic antagonists
Bronchodilation, decrease in bronchial secretions
Respiratory
organ affected by muscarinic antagonists
Relaxation, decrease motility, antidiarrheal, prolongs gastric
emptying time
GIT
organ affected by muscarinic antagonists
Relaxation of the bladder wall, urinary retention
gut
organ affected by muscarinic antagonists
Decrease secretion, salivation, lacrimation, sweating
gland
organ affected by muscarinic antagonists
None
skeletal muscle