Indirect ACh receptor agonists 2 (quasi-revers cholinesterase inh + 5 PDE)

Question 1

Quasi-reversible cholinesterase inhibitors (organophosphate compounds) - 3 drugs, 2 toxins

Answer 1

Echothiophate
Isoflurophate
Malathion
Toxins: soman and sarin

Question 2

Organophosphates - MOA

Answer 2

Binds tightly to the catalytic site of cholinesterase and is hydrolyzed very slowly. The intermediate is stabilized in the process of aging.

Question 3

Organophosphate poisoning - symptoms

Answer 3

Salivation, lacrimation.
Miosis, accommodative spasm.
Bronchoconstriction.
Intestinal cramps, urinary incontinence.
Muscle weakness, neuromuscular blockade.
Seizures, respiratory depression and coma.

Question 4

Echothiophate - indications

Answer 4

Chronic glaucoma that does not respond to other drugs.
Accommodative esotropia (strabismus/ocular deviation).

Question 5

Malathion - indications

Answer 5

Head lice

Question 6

Management of organophosphate poisoning

Answer 6

Decontamination of the patient.
Cardiovascular and respiratory support.
Atropine and pralidoxime.

Question 7

Pralidoxime - MOA

Answer 7

Its high affinity for phosphorus breaks the bond between cholinesterase and organophosphates. This regenerates cholinesterase.

Question 8

Type 5 phosphodiesterase (5-PDE) inhibitors (3 drugs)

Answer 8

Sildenafil
Tadalafil
Vardenafil

Question 9

5-PDE inhibitors - indications

Answer 9

Erectile dysfunction

Question 10

Sildenafil - indications

Answer 10

Pulmonary arterial hypertension

Question 11

Tadalafil - indications

Answer 11

Pulmonary arterial hypertension

Benign prostate hyperplasia

Question 12

Type 5 phosphodiesterase inhibitors - MOA

Answer 12

Inhibits typer 5 phosphodiesterase, and decreases the breakdown of cGMP. This potentiates the vasodilative effect of ACh from parasympathetic neurons in the pelvic plexus.

Question 13

Type 5-phosphodiesterase inhibitors - adverse effects

Answer 13

Headache, nasal congestion, dyspepsia, myalgia, back pain, visual disturbances.
Reduced supine blood pressure.

Question 14

Type 5-phosphodiesterase inhibitors should not be taken with, and why

Answer 14

Nitroglycerin or other organic nitrate: profound hypotension, reflex tachycardia, worsening of angina pectoris.
Vasodilators (α-adrenceptor antagonists): hypotension.

Question 15

Drugs that increase levels of type 5-phosphodiesterase inhibitors

Answer 15

CYP3A4 inhibitors: Cimetidine, erythromycin, ketoconazole, itraconazole.