Drugs Affecting Cholinergic Function

Question 1

Functions of the Parasympathetic Nervous System

Answer 1

• Slowing of HR
• Increased gastric secretion
• Emptying of the bladder
• Emptying of the bowel
• Focusing the eye for near vision
• Constricting the pupil
• Contracting bronchial smooth muscle

Question 2

Sites of drug action in the PSNS

Answer 2

• 1. The synapses between preganglionic neurons and postganglionic neurons
• 2. The junctions between postganglionic neurons and their effector organs

Question 3

What neurotransmitter is associated with the PSNS?

Answer 3

Acetylcholine (preganglionic and postganglionic neurotransmitter)

Question 4

Function of cholinergic receptors

Answer 4

Mediate response to acetylcholine

Question 5

Three subtypes of cholinergic receptors

Answer 5

Muscarinic, NicotinicM, NicotonicN

Question 6

Activation of NicotinicN (neuronal) receptor

Answer 6

Promotes ganglionic transmission, promotes release of norepinephrine from adrenal medulla

Question 7

Activation of Nicotinic M (muscle) receptor

Answer 7

Causes contraction of skeletal muscle

Question 8

Activation of Muscarinic receptor

Answer 8

located on target organs, binding causes organ response

Question 9

Drugs that stimulate the PSNS receptors are called…

Answer 9

Stimulants, agonists, cholinergic drugs

Question 10

Drugs that block the PSNS receptors are called…

Answer 10

Blockers, antagonists, anticholinergic drugs

Question 11

Excess cholinergic effects

Answer 11

• Decreased intraocular pressure (cholinergic drugs are used to treat glaucoma)
• Mitosis (constriction of pupil)
• Sweating - WET
• Increased salivation
• Increased bronchial secretions – increased risk for pneumonia or other respiratory infections
• Bronchial constriction – increased risk for asthmatic patients
• Increased GI tone
• Diarrhea
• Decreased blood pressure
• Bradycardia
• Contraction of bladder detrusor muscle

Question 12

Excess anticholinergic effects

Answer 12

• Increased intraocular pressure
• Mydriasis (dilation of pupils)
• Photophobia – light sensitivity
• Decreased sweating – fluid and electrolyte issues
• Dry mouth
• Decreased bronchial secretions
• Respiratory depression
• Decreased GI motility with possible constipation
• Decreased BP (compensatory mechanism for tachycardia) followed by increased BP
• Tachycardia and, possibly, palpitations
• Urinary retention
• Vasodilation
• Drowsiness, confusion, and agitation – elderly are at risk

Question 13

Anticholinergic Poisoning

Answer 13

• Mad as a hatter
• Blind as a bat
• Red as a beet
• Dry as a bone

Question 14

Pilocarpine

Answer 14

Direct-acting cholinergic – agonist, stimulates acetylcholine directly

Question 15

Pilocarpine is typically used for…

Answer 15

• Topical pharmacotherapeutics
• Simple and acute glaucoma
• Preoperative and postoperative elevated intraocular pressure
• Drug-induced mydriasis

Question 16

Nicotine

Answer 16

• Stimulates the CNS
• Pharmacotherapeutics are limited to preparations to assist in smoking cessation
• Adverse effects are related to its effects on the cardiovascular system (tachycardia, hypertension) and CNS
• If a person has had a cigarette within a 30-minute timeframe of taking his/her blood pressure, it will be elevated – after 30 minutes; the blood pressure should come back to normal

Question 17

Neostigmine

Answer 17

• Indirect-acting cholinergic drug
• Acts by reversibly inhibiting postsynaptic cholinesterase (enzyme that degrades acetylcholine)
• Used in the treatment of myasthenia gravis to minimize muscle fatigue
• Most serious adverse effect: cholinergic crisis

Question 18

Atropine

Answer 18

• Anticholinergic drug
• Antidote to cholinergic poisoning
• Pharmacotherapeutics:
  - Preoperatively to dry secretions
  - Acute cardiac emergencies
  - Topically (homatropine) to treat ophthalmic disorders
  - Treatment of motion sickness and diarrhea (Lomotil)
• Adverse effects related to loss of acetylcholine stimulation on receptors
• Most serious adverse effect: Anticholinergic overdose (poisoning)