Atropine may cause a rise in body temperature (atropine fever):

Correct Answer: C

Rationale: The correct answer is C because infants and children are more sensitive to atropine's effects, including the potential for causing a rise in body temperature. Atropine inhibits sweat gland function, leading to decreased ability to regulate body temperature, especially in pediatric populations. Choice A is incorrect because atropine fever can occur in adults as well. Choice B is incorrect because pregnancy status does not directly affect the likelihood of atropine-induced fever. Choice D is incorrect because not all adults experience atropine fever, while infants and children are more susceptible.

Correct Answer: A

Rationale: The correct answer is A: Yohimbine. Yohimbine is an alpha2-selective antagonist because it specifically blocks alpha2-adrenergic receptors. This leads to increased sympathetic activity since alpha2 receptors normally inhibit sympathetic activity when activated. B: Tamsulosin is an alpha1-selective antagonist used to treat benign prostatic hyperplasia. C: Tolazoline is a non-selective alpha-adrenergic antagonist, affecting both alpha1 and alpha2 receptors. D: Prazosin is an alpha1-selective antagonist used to treat hypertension and benign prostatic hyperplasia. In summary, yohimbine is the correct answer because it selectively blocks alpha2 receptors, while the other choices are either alpha1-selective or non-selective alpha antagonists.

Correct Answer: C

Rationale: The correct answer is C: Thyopental. Thyopental is a barbituric acid derivative known for its hypnotic properties by inducing sleep. Flurazepam (A) is a benzodiazepine used for treating insomnia. Zaleplon (B) is a non-benzodiazepine hypnotic agent. Triazolam (D) is also a benzodiazepine used for insomnia. Therefore, the correct choice is C as it is the only barbituric acid derivative among the options.

Correct Answer: A

Rationale: The correct answer is A because phenytoin blocks sodium channels, inhibiting the abnormal firing of neurons seen in epilepsy. This action helps to stabilize neuronal membranes and prevent seizures. Options B, C, and D are incorrect as phenytoin does not bind to GABA receptors, affect Ca2+ currents, or inhibit GABA-transaminase. These mechanisms are associated with different antiepileptic drugs.

Correct Answer: B

Rationale: The correct answer is B because carbidopa inhibits dopa decarboxylase enzyme, preventing the conversion of levodopa into dopamine outside the brain. This allows more levodopa to reach the brain and be converted into dopamine, improving its efficacy in treating Parkinson's disease. Choice A is incorrect as carbidopa does not directly affect the synthesis, release, or reuptake of dopamine. Choice C is incorrect because carbidopa does not stimulate dopamine receptors but rather works on the enzymatic conversion of levodopa to dopamine. Choice D is incorrect as carbidopa does not inhibit catechol-O-methyltransferase (COMT), which is another enzyme involved in dopamine metabolism.