Which eicosanoid is most associated with labor due to its effect on uterine contractions?

Correct Answer: A

Rationale: The correct answer is A: Prostaglandins. Prostaglandins are most associated with labor as they play a key role in promoting uterine contractions. They are synthesized in the uterus and stimulate smooth muscle contractions, leading to the initiation and progression of labor. Thromboxanes primarily regulate platelet function and vasoconstriction, not uterine contractions. Leukotrienes are involved in inflammatory responses and immune regulation, not specifically labor. NSAIDs inhibit prostaglandin synthesis, which can hinder labor progression, making them an unlikely choice for promoting uterine contractions.

Correct Answer: D

Rationale: The correct answer is D because drugs exhibiting zero-order kinetics have a linear plot of drug concentration versus time. In zero-order kinetics, the rate of drug elimination remains constant regardless of drug concentration, leading to a linear decrease in drug concentration over time. Choice A is incorrect as first-order kinetics are more common. Choice B is incorrect as zero-order kinetics show a constant rate of elimination, not exponential decrease. Choice C is incorrect as the half-life of drugs exhibiting zero-order kinetics is dose-dependent.

Correct Answer: A

Rationale: The correct answer is A because highly bound drugs (98% bound) do not have clinically significant drug-drug interactions through displacement from binding sites on plasma proteins. This is because only the unbound (free) fraction of a drug is pharmacologically active and available for interactions. Highly bound drugs are bound to proteins and not readily available for interactions. Regarding the other choices: B: Only free drugs can pass through glomerular filtration - Correct, as only unbound drugs can be filtered through the kidneys. C: Only free drugs become available for hepatic metabolism - Correct, as only unbound drugs can undergo metabolism in the liver. D: Only free drugs can distribute to peripheral tissues - Correct, as only unbound drugs can leave the bloodstream and reach peripheral tissues.

Correct Answer: C

Rationale: The correct answer is C: Half-life (t1/2). Half-life is the time required for the concentration of a drug in plasma to decrease by half during elimination. It is a measure of how quickly a drug is removed from the body. It is independent of dose or concentration. Absorption time (A) is the time it takes for a drug to enter the bloodstream. Metabolic time (B) refers to the time it takes for a drug to be metabolized in the body. Clearance time (D) is the time it takes for the body to clear a certain amount of drug from the plasma, but it does not specifically indicate the time required for half of the drug to be eliminated.

Correct Answer: A

Rationale: The correct answer is A: Docusate sodium. It is a stool softener commonly used during pregnancy due to its safety profile. It helps to soften the stool, making it easier to pass without straining, which is important in preventing constipation. B: Magnesium citrate is not recommended during pregnancy due to its potential to cause diarrhea and electrolyte imbalance. C: Castor oil is not recommended during pregnancy as it can induce labor and has potential side effects. D: Mineral oil is not recommended during pregnancy due to its potential to interfere with nutrient absorption and cause aspiration pneumonia if accidentally inhaled.