Muscarinic receptor antagonists 1 (Belladonna alkaloids)

Question 1

Muscarinic receptor antagonists are also known as… (and why)

Answer 1

Parasympatholytic drugs, because they compete with and inhibit ACh function at parasympathetic neuroeffector junctions.

Question 2

Parasympatholytic drugs (2 groups)

Answer 2

Belladonna alkaloids.

Semisynthetic and synthetic drugs.

Question 3

Belladonna alkaloids (3 drugs)

Answer 3

Atropine
Scopolamine
Hyoscyamine

Question 4

Most serious adverse effects of belladonna alkaloids

Answer 4

Poisoning (highly toxic).

Question 5

Atropine and scopolamine - what can increase their duration of action?

Answer 5

Topical ocular administration: they bind to pigments in the iris.

Question 6

Signs of atropine toxicity

Answer 6

“Dry as a bone, blind as a bat, red as a beet, mad as a hatter.”
0.5 mg: Dry mouth, decreased sweating.
1 mg: Increased heart rate, very dry mouth, thirst.
2 mg: Blurred vision, tachycardia, palpitations.
5 mg: Urinary retention, hot + dry skin, restlessness, fatigue.
10 mg: Rapid + weak pulse, ataxia, hallucinations, delirium, coma.

Question 7

Effects of atropine and scopolamine (3 ocular, 2 cardiac, 1 secretory)

Answer 7

Pupillary dilation (mydriasis), paralysis of accommodation (cycloplegia), inhibition of lacrimal gland secretion (dry eyes).
Increase heart rate, increase AV conduction velocity.
Inhibit sweating.

Question 8

What may happen when low doses of atropine are given intravenously?

Answer 8

Paradoxical slowing of heart rate due to stimulation of the vagal motor nucleus in the brain stem.

Question 9

Effects of atropine and scopolamine (3 gastric, 1 urinary, 2 CNS)

Answer 9

Reduce intestinal motility, increase intestinal transit time, inhibit gastric acid secretion.
Relaxes detrusor muscle.
Sedation and excitement

Question 10

Side effects of belladonna alkaloids

Answer 10

Dry eyes
Gastroesophageal reflux
Cycloplegia
Constipation
Urinary retention
Delirium
Hallucinations
Hyperthermia and hot, dry and flushed skin (esp children)

Question 11

Which belladonna alkaloid is most sedating?

Answer 11

Scopolamine

Question 12

Scopolamine - indications

Answer 12

Adjunct to anesthesia.
Motion sickness (transdermal formulation)

Question 13

Atropine and scopolamine - indications (4 ocular, 1 respiratory)

Answer 13

Ophthalmic examinations (that require mydriasis).
Determination of refractive errors (esp young pt)
Iritis and cyclitis.
Reduce salivary and respiratory secretions during general anesthesia.

Question 14

Atropine - indications

Answer 14

Sinus bradycardia (IV or endotracheal injection).

Question 15

Atropine is no longer used for … because…

Answer 15

Not used for asthma because it impairs ciliary activity and may cause accumulation of viscid material in the airways.

Question 16

Atropine and scopolamine - indications (1 GI, 1 urinary, 1 CNS,

Answer 16

Relieve intestinal spasms and pain.
Overreactive bladder.
Parkinson disease.

Question 17

Scopolamine - mechanism of preventing motion sickness

Answer 17

Block ACh neurotransmission from vestibular apparatus to the vomiting center in the brain stem.

Question 18

Atropine and glycopyrrolate - indications

Answer 18

Myasthenia gravis.
Cholinesterase inhibitors (supranormal doses).
Reduce salivary and respiratory secretions during general anesthetics.
Symptomatic AV block.

Question 19

Hyoscyamine - indications and administration route

Answer 19

Oral or sublingual adm for intestinal cramps