Analgin usefulness is limited by:

Correct Answer: A

Rationale: The correct answer is A: Agranulocytosis. Analgin can cause a serious side effect called agranulocytosis, which is a condition where the bone marrow stops producing enough white blood cells, leaving the body vulnerable to infections. This limits the usefulness of Analgin as the risk of developing agranulocytosis outweighs its benefits. Summary of other choices: B: Erosions and gastric bleeding - While Analgin can cause gastrointestinal side effects like erosions and bleeding, these are not as severe or limiting as agranulocytosis. C: Methemoglobinemia - Although Analgin can lead to methemoglobinemia, it is a rare side effect compared to agranulocytosis. D: Hearing impairment - There is no significant evidence linking Analgin to hearing impairment, making this choice incorrect.

Correct Answer: A

Rationale: The correct answer is A because caffeine actually stimulates gastric secretion, not inhibits it. Caffeine can increase stomach acid production, leading to potential digestive issues. Choices B, C, and D are incorrect because caffeine is known to cause hyperglycemia by increasing blood sugar levels, has a moderate diuretic action by increasing urine production, and increases free fatty acids in the bloodstream, which can affect metabolism. Therefore, based on its effects on gastric secretion, A is the correct answer.

Correct Answer: B

Rationale: The correct answer is B: More addictive and fast-acting. Heroin is derived from morphine and is more potent, leading to a faster onset of action and increased addictive potential. The rapid crossing of the blood-brain barrier contributes to its fast-acting properties. It is crucial to differentiate between heroin and morphine due to their varying addictive nature and speed of action. Choices A, C, and D are incorrect because heroin is not typically used clinically, is not more effective orally, and is actually more potent and faster-acting than morphine, making it not less potent and long-acting.

Correct Answer: B

Rationale: Step 1: Ketamine is the correct choice for dissociative anesthesia due to its unique mechanism of action, which involves blocking NMDA receptors, leading to dissociation of sensory input from conscious perception. Step 2: Midazolam (A) is a benzodiazepine used for sedation and anxiolysis, not dissociative anesthesia. Step 3: Fentanyl (C) is an opioid analgesic used for pain control, not dissociative anesthesia. Step 4: Thiopental (D) is a barbiturate used for induction of general anesthesia, not specifically for dissociative anesthesia.

Correct Answer: D

Rationale: The correct answer is D: Apomorphine hydrochloride. Apomorphine hydrochloride is not an antiemetic; it is a dopamine agonist primarily used to treat Parkinson's disease. Metoclopramide, Ondansetron, and Chlorpromazine are all antiemetic drugs that work by different mechanisms to alleviate nausea and vomiting. Metoclopramide acts as a dopamine antagonist and 5-HT3 receptor antagonist, Ondansetron is a selective 5-HT3 receptor antagonist, and Chlorpromazine is a dopamine antagonist with antiemetic properties. Therefore, D is the correct answer as it does not belong to the class of antiemetic drugs.