The dose-related adverse effect of ethosuximide is:

Correct Answer: A

Rationale: The correct answer is A: Gastrointestinal reactions, such as anorexia, pain, nausea, and vomiting. Ethosuximide is primarily used to treat absence seizures. Its common side effects include gastrointestinal reactions due to its irritant effect on the gastric mucosa. Anorexia, pain, nausea, and vomiting are commonly reported adverse effects. Exacerbated grand mal epilepsy (choice B) is not a known adverse effect of ethosuximide. Transient lethargy or fatigue (choice C) is a common side effect, but it is not dose-related. Therefore, the correct answer is A, as it accurately reflects the dose-related adverse effect of ethosuximide, while the other choices do not.

Correct Answer: D

Rationale: Alcohol causes an acute increase in the local concentrations of dopamine, opioid, and serotonin. Alcohol consumption leads to the release of dopamine, which is associated with pleasure and reward. It also activates the opioid system, contributing to its addictive properties. Additionally, alcohol affects the serotonin system, influencing mood regulation. Therefore, all of the above choices are correct because alcohol impacts the local concentrations of dopamine, opioid, and serotonin simultaneously.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Orthostatic hypotension can occur due to various mechanisms, such as central action of phenothiazines causing vasodilation, inhibition of norepinephrine uptake leading to decreased vasoconstriction, and alpha adrenoreceptor blockade reducing sympathetic response. Each of these factors can contribute to a drop in blood pressure upon standing. Choices A, B, and C all play a role in the development of orthostatic hypotension, making option D the correct comprehensive answer.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Highly selective serotonin reuptake inhibitors (SSRIs) target the reuptake of serotonin specifically. Sertraline, paroxetine, and fluoxetine are all SSRIs. They do not significantly affect other neurotransmitters, making them highly selective. Therefore, all three choices are correct as they are all examples of highly selective serotonin reuptake inhibitors.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Flumazenil is a competitive antagonist of BZ receptors by binding and blocking their activity. 2. Buspirone is a partial agonist at serotonin receptors, not BZ receptors. 3. Picrotoxin is a non-competitive antagonist at GABA receptors, not BZ receptors. 4. Diazepam is a positive allosteric modulator at BZ receptors, not a competitive antagonist. Summary: Flumazenil is the correct answer as it specifically targets BZ receptors as a competitive antagonist, while the other options act on different receptors or in different ways.