Which one of the following local anesthetics causes methemoglobinemia?

Correct Answer: A

Rationale: Prilocaine is the correct answer as it can cause methemoglobinemia due to its metabolite o-toluidine. This metabolite oxidizes hemoglobin to methemoglobin, leading to reduced oxygen-carrying capacity. Procaine, lidocaine, and ropivacaine do not typically cause methemoglobinemia as they lack the metabolites responsible for this condition. So, prilocaine is the only local anesthetic among the choices that can lead to methemoglobinemia.

Correct Answer: D

Rationale: Sympathetic stimulation involves the activation of the sympathetic nervous system. Norepinephrine is released from sympathetic nerve terminals, activating adrenoreceptors on postsynaptic sites. Additionally, the adrenal medulla releases epinephrine into the bloodstream. Therefore, all three choices (A, B, and C) are mechanisms through which sympathetic stimulation is mediated. Hence, the correct answer is D. The other choices (A, B, and C) are incorrect as they individually represent different aspects of sympathetic stimulation, but the correct answer encompasses all of them.

Correct Answer: D

Rationale: Step 1: Long-acting decongestants are preferred for sustained relief. Step 2: Xylometazoline has a longer duration of action compared to other choices. Step 3: Epinephrine and norepinephrine are short-acting sympathomimetic agents. Step 4: Phenylephrine is intermediate-acting, not long-acting. Step 5: Therefore, D (Xylometazoline) is the correct choice for long-acting topical decongestant agents.

Correct Answer: C

Rationale: The correct answer is C: Reserpine. Reserpine is a rauwolfia alkaloid acting as an adrenoreceptor antagonist by inhibiting the storage of norepinephrine and serotonin in vesicles. Prazosin (A) is an alpha-1 adrenergic receptor antagonist, Propranolol (B) is a non-selective beta-adre, Phentolamine (D) is a non-selective alpha-adrenergic receptor antagonist, making them all incorrect choices.

Correct Answer: D

Rationale: The correct answer is D. Antiseizure drugs work through multiple mechanisms to prevent seizures. 1. A: Antiseizure drugs enhance GABAergic transmission, increasing inhibition in the brain. 2. B: They also diminish excitatory glutamatergic transmission, reducing neuronal excitation. 3. C: Antiseizure drugs modify ionic conductance to stabilize neuronal activity. Therefore, the correct answer is D, as antiseizure drugs act through all the mentioned mechanisms to prevent seizures effectively. Choices A, B, and C are incorrect because they do not encompass the comprehensive range of mechanisms involved in the action of antiseizure drugs.