Which of the following is the most effective in the management of absence seizures?

Correct Answer: D

Rationale: Absence seizures, brief lapses in consciousness, require specific antiepileptics. Carbamazepine, effective for focal seizures, can worsen absence seizures by enhancing sodium channel activity. Topiramate and clobazam have broader uses but limited efficacy here. Phenytoin suits tonic-clonic, not absence. Ethosuximide reduces T-type calcium currents in thalamic neurons, directly targeting absence seizure mechanisms, making it most effective. Its specificity ensures rapid control, critical for pediatric epilepsy management.

Correct Answer: A

Rationale: Aging reduces creatinine clearance in about two-thirds of individuals due to declining renal function, a true statement impacting drug excretion. Body fat increases, not decreases, with age, altering distribution of lipophilic drugs, so that's false. Total body water decreases, not increases, affecting hydrophilic drugs. Conjugation (phase II) is less affected than oxidation (phase I) by age, making that false. Absorption isn't significantly altered by age alone. Reduced renal clearance is a critical age-related change, necessitating dose adjustments for renally cleared drugs like digoxin.

Correct Answer: A

Rationale: Levodopa is a prodrug converted to dopamine in the brain, bypassing the blood-brain barrier. Prodrugs are inactive compounds metabolized into active drugs in the body.

Correct Answer: B

Rationale: Oral decongestants cause systemic effects like hypertension, unlike nasal ones risking rebound. Efficacy (choices A, D) varies, rebound is nasal-specific. B highlights the key difference, making it correct.

Correct Answer: C

Rationale: Diffusion moves drugs passively from high to low concentration across membranes, like oral absorption, a pharmacokinetic staple. Active transport uses energy against gradients. Osmosis is water-specific. Metabolism alters drugs chemically. Diffusion fits, driving initial uptake.