Pharmacology MCQs- 251

Q- Which of the following explains the benefit of lactulose in hepatic encephalopathy?

A- Lactulose antagonizes the action of ammonia on hepatic cells

B- Lactulose is converted to lactic acid by intestinal bacteria, which decreases ammonia

C- Lactulose decreases the stress on the liver to produce glucose

D- Lactulose removes circulating toxins from the blood

B- Lactulose is converted to lactic acid by intestinal bacteria, which decreases ammonia- In the colon, lactulose is broken down by bacteria into lactic acid and other organic acids. This acidifies the gut lumen, converting ammonia (NH₃) into ammonium (NH₄⁺), which cannot be absorbed and is excreted. This lowers blood ammonia levels and improves hepatic encephalopathy.

Q- Which of the following histamine H1 antagonists is identified for its serotonin-blocking effect?

A- Cyproheptadine

B- Desloratadine

C- Fexofenadine

D- Loratadine

A- Cyproheptadine- Cyproheptadine is an H1 antihistamine with strong serotonin-blocking (5-HT2 antagonist) properties. It is used in conditions like serotonin syndrome and sometimes to stimulate appetite. Desloratadine, fexofenadine, and loratadine do not have significant serotonin-blocking effects.

Q- Which one of the following drugs is a selective beta-1 agonist?

A- Amrinone

B- Digoxin

C- Dobutamine

D- Dopamine

C- Dobutamine- Dobutamine is a selective β1-adrenergic agonist that increases heart rate and contractility with minimal effect on β2 or α receptors. Amrinone is a phosphodiesterase inhibitor, digoxin increases cardiac contractility via Na⁺/K⁺ ATPase inhibition, and dopamine affects multiple receptors depending on dose, not selectively β1.