The following are H1 receptor antagonist, except :

Correct Answer: D

Rationale: Terfenadine is a second-generation antihistamine, but it is not an H1 receptor antagonist like the other options listed. Terfenadine was once used for the treatment of allergic conditions, but it is known for its potential to cause cardiac side effects due to its interaction with other medications and prolongation of the QT interval. Consequently, terfenadine has been largely replaced by newer, safer antihistamines. The rest of the options listed (chlorpheniramine, promethazine, cimetidine, and diphenhydramine) are all H1 receptor antagonists commonly used to block the action of histamine and relieve symptoms of allergies.

Correct Answer: B

Rationale: Meperidine hydrochloride (Demerol) is an opioid analgesic commonly used for post-operative pain management. The common side effects of meperidine include tremors, sweating, and dizziness. Diarrhea is not a common side effect associated with meperidine use. Opioid analgesics like meperidine more commonly cause constipation rather than diarrhea. Therefore, choice B is the correct answer as the side effect of diarrhea is not typically seen with meperidine administration.

Correct Answer: B

Rationale: Prazosin, an alpha-1 blocker, acts peripherally, not on the vasomotor center. Methyldopa, a centrally acting α2 agonist, reduces sympathetic outflow from the vasomotor center, a true statement lowering blood pressure. Hydralazine dilates arteries directly, not centrally. Reserpine depletes catecholamines peripherally and centrally but isn't primarily vasomotor-focused. Losartan (likely misspelled) is an ARB, peripheral. Methyldopa's central action is key in pregnancy hypertension, offering a unique mechanism among antihypertensives.

Correct Answer: D

Rationale: Nasal decongestants risk rebound beyond 5 days; spitting excess avoids systemic effects (correct answers: 1, 3, 5). Water isn't relevant. D ensures safe use, making it key.

Correct Answer: D

Rationale: Terfenadine is a second-generation antihistamine, but it is not an H1 receptor antagonist like the other options listed. Terfenadine was once used for the treatment of allergic conditions, but it is known for its potential to cause cardiac side effects due to its interaction with other medications and prolongation of the QT interval. Consequently, terfenadine has been largely replaced by newer, safer antihistamines. The rest of the options listed (chlorpheniramine, promethazine, cimetidine, and diphenhydramine) are all H1 receptor antagonists commonly used to block the action of histamine and relieve symptoms of allergies.