40)M-cholinomimetics Flashcards
1
Q
M-Cholinolytics
A
Drugs that act on the parasympathetic nervous system (PNS)
2 categories ⇢ Anti-muscarinic + Anti-nicotinic
ACh ⇢ NT in PNS neural pathway
- Released from post ganglionic neurons + binds to muscarinic receptor
2
Q
Classification
A
Natural alkaloids
- Atropine (spasmolytic) + Scopolamine
Semisynthetic derivatives
- Mydriatics + Homatropine
Synthetic compounds
- GI spasmolytic ⇢ Oxyphenonium
- Anti-ulcus drugs ⇢ Pirenzepine
- Anti-asthmatics ⇢ Ipratropium + Tiotropium
3
Q
Pharmacodynamics
A
Work as competitive antagonists
- Blocking effect can be overcome by ⇡ [muscarinic agonist]
They supress PNS + Allow SS to dominate:
- Cardiovascular ⇢ ⇣HR + ⇣ Force of contraction
- Eye ⇢ Binds on M-receptors in muscles of eye ⇢ Pupillary constriction + ⇣ intra-ocular pressure via ⇡ aq humour drainage
- GI tract ⇢ relaxes GI smooth muscle + supresses secretion
4
Q
Pharmacokinetics
A
- Action + metabolism of cholinergic agonists depends on ⇢ affinity of drug for M/N receptors
Atropine
- Lipid soluble
- Crosses membrane barriers
- Elimination ⇢ Partially metabolised in liver + partially by renal excretion
5
Q
Clinical uses
A
Atropine
- Treat spastic disorders of GI
- Supress respiratory secretions prior to surgery
Scopolamine
- Produces amnesia + sedation in obstetrics
- Prevents motion sickness
Ipratropium
- Treats asthma
6
Q
Adverse effects
A
Acute constipation
Dizziness
Nausea
Difficulty swallowing
Oral ulcers
Edema of nasal cavity
