This document discusses cholinergic drugs, including their types and mechanisms of action. It describes muscarinic agonists like acetylcholine, carbachol, and pilocarpine that act directly on muscarinic receptors to cause miosis, accommodation, and increased aqueous outflow. Indirect acting muscarinic drugs like cholinesterase inhibitors are also discussed. The document also covers muscarinic antagonists that cause pupil dilation and paralysis of accommodation, as well as nicotinic drugs like edrophonium and neuromuscular blockers. Side effects of various cholinergic drugs are provided.

1. Cholinergic Drugs
Dr Azmat Khan
Lecturer:
The University of Lahore
(Islamabad Campus)
Email:opt.azmat@gmail.com
1

2. Ach Synthesis: 2

3. Nervous system 3

4. Types of Cholinergic Receptors 4

5. Muscarinic Receptors 5

6. Nicotinic Receptors 6

7. Muscarinic Agonist
 Direct acting agonist ……. Directly act on Ach receptor
Three action ---------
1) Miosis , ( sphincter pupillae )
2) Accommodation and ( ciliary muscle )
3) Increase aqueous outflow.( longitudinal fibers of CM .. Tension on scleral
spur ….. Opening of TM .
Examples. Acetycholine
Carbachol
Pilocarpine etc
7

8. Acetycholine.
Acetylcholine : does not penetrate corneal epi…well ,
> rapidly degraded by acetylcholinesterase ,
>not used topically ,
>1% use in ant seg surgery Intracameral.
Note: Produce prompt and marked miosis .
8

9. Carbachol.
 0.01% carbachol is 100 times more effective and long lasting than Ach.
 Maximal miosis within 5 min .
 Last for 24 hr.
 An effective hypotensive drug.
9

10. Pilocarpine.
 0.12% used diagnostically to confirm Adie tonic pupil.
 Denervated iris exhibit , hypersensitivity and response well .
 Normal iris doe not response .
 0.25% , 0.5% upto 6% ( 4 times daily in case of POAG) and also in pt with
PACG.
 NOTE: 4% is contraindicated in acute attack of angle closure glaucoma ,,,
closing the angle.
10

11. SIDE EFFECT.
 MIOISIS & induce Accommodation ….. Scotopic vision, central lens opacity
, myopia , RD
 Cataractogenis …
 Miotic iris cyst .
 Other systemic adverse effect … salivation , diarrhea , urinay urgency ,
vomiting , bronchial spasm, bradycardia & diaphoresis.
11

12.  Miotic agent and accommodative esotropia ??
12

13. Muscarinic Drugs.
 Indirect acting agonist:
 Cholinesterase inhibitor . ( forming an enzyme-inhibitor complex )
 Longer duration of actions as compared to direct acting agonist .
 Twice daily treatment is sufficient.
 Reversible inhibitor ( physostigmine , neostigmine and edrophonium)
 Irrersible inhibitor ( echothiophate , diisopropyl phosphorofluoridate )
13

14. Con…
 The action of phosphorylating cholinesterase inhibitors can be reversed on
an acute basis by treatment with oxime containing compound like
pralidoxime .
14

15. Con..
 Note: pt receiving long term , irreversible cholinterase inhibitor therapy
such as echothiopate may experience toxic reaction from systemic
absorption by local anesthetic containing ester group (procaine)that are
normally inactivated by plasma cholinesterase.
 Same for succinylcholine during induction of GA …. Respiratory paralysis .
 Not combine with direct acting cholinergic agonist .
 Were use in past for treatment of lice infestation of eyelashes .
 No longer available for ophthalmic use in US.
15

16. Muscarinic Antagonists
 Paralysis of iris sphincter …. Unopposed action of dilator muscle, causing
pupillary dilation & same for relaxation of Accommodation.
 Uses:
 Examination of peripheral lens, CB & Retina.
 Cycloplegic refraction and Iritis
 Reduce blood-aqueous permeability , hence use in ocular inflammatory
disease.
 Examples: Atropine
Cyclopentolate ,Tropicamide
Scopolamine & Homatropine.
16

17.  Relive pain in case of iridocylitis.
 Treat ciliary block glaucoma.
 Note: use of these drug to dilate the pupil of pt with POAG may elevate
IOP.
17

18. Adverse effect:
 Local irritation with swelling.
 Conjuctival hyperemia.
 Photophobia and blurring of vision.
 Systemic effect:
especially in children are, flushing , fever, tachycardia , constipation ,
urinary retention.
Note: in mild cases only discontinuation of the drug while in severe cases IV
physostigmine.
18

19. Nicotinic Drugs.
 Indirect acting agonist: Edrophonium
 Use in the diagnosis fo MG.
 Nicotinic Antagonist: (neuromuscular blocking agent)
 To facilitate intubation in GA.
 Two types of anatognists,
 1) nondepolarizing agent ( gallamine & pancuronium )
 2) depolarizing agent. ( succinylcholine & decamethonium)
19

20. Nicotinic antagonist.
 Note: in singly innervated muscle fibers , depolarization and contraction
followed by prolonged unresponsiveness and flaccidity, while in case of
multiply innervated fiber ( one-fifth of EOM) such contractions of EOM
exert force on the globe.
 Avoid such drug in GA in operation on lacerated eyes.
20

21. 21