Digoxin has a half-life of approximately 40 hours if renal function is normal. How long will it take to reach >90 per cent of the steady state plasma concentration?

Correct Answer: B

Rationale: Steady-state concentration is reached after 4-5 half-lives, when drug input equals output. Digoxin's half-life is 40 hours (1.67 days). Four half-lives is 4 × 40 = 160 hours (6.67 days), and five is 200 hours (8.33 days). Over 90% steady state occurs around 4 half-lives, roughly 6-7 days. Two days (48 hours) is only ~1.2 half-lives, far too short. Ten days (~6 half-lives) exceeds 90%, but 7 days (~4.2 half-lives) aligns with >90% (e.g., 94% at 4 half-lives). Fourteen or 18 days overshoot unnecessarily. Seven days balances precision and practicality, guiding digoxin dosing timelines in heart failure or arrhythmias.

Correct Answer: A

Rationale: Terazosin, an alpha-1 adrenergic blocker, treats both hypertension and benign prostatic hyperplasia (BPH) by relaxing smooth muscle in blood vessels and the prostate, lowering blood pressure and easing urinary symptoms. Sildenafil, used for erectile dysfunction, doesn't address hypertension or BPH and may cause hypotension, making it unsuitable here. Finasteride, a 5-alpha reductase inhibitor, shrinks the prostate for BPH but has no effect on blood pressure, missing the dual need. Tamsulosin, another alpha-1 blocker, relieves BPH symptoms but isn't typically used for routine hypertension management and risks severe hypotension. Terazosin's dual action makes it uniquely safe and effective, addressing both conditions without exacerbating either, unlike the others, which lack hypertensive benefits or pose risks in this context.

Correct Answer: C

Rationale: A loading dose rapidly achieves therapeutic levels, followed by a lower maintenance dose, a standard approach explained clearly here. Half-life isn't shortened-it's about concentration. ‘Always' oversimplifies. Side effect reduction isn't the goal-efficacy is. The larger initial dose's purpose reassures the patient, aligning with pharmacokinetic principles for quick action.

Correct Answer: A

Rationale: Pregnancy boosts lung perfusion, increasing inhaled drug absorption (e.g., anesthetics), a pharmacokinetic shift to note. Excretion may slow later, but not universally. Oral absorption isn't broadly reduced-GI changes vary. Avoiding all drugs is impractical-some conditions need treatment. Inhaled absorption informs safe use.

Correct Answer: C

Rationale: The correct answer is C) CNS stimulants. In the treatment of ADHD, CNS stimulants like methylphenidate and amphetamines are commonly prescribed. These medications work by increasing the levels of certain neurotransmitters in the brain, leading to improved focus, attention, and impulse control in individuals with ADHD. Option A) CNS depressants, such as benzodiazepines, have a sedative effect and are not typically used in the treatment of ADHD. Using CNS depressants can worsen symptoms by further reducing alertness and attention. Option B) Parasympathomimetics affect the parasympathetic nervous system and are not indicated for treating ADHD. These medications can cause side effects like bradycardia and excessive salivation, which are not beneficial in managing ADHD symptoms. Option D) Sympathomimetics stimulate the sympathetic nervous system but are not the primary choice for treating ADHD. While some sympathomimetics may have effects on attention and focus, they are not as effective or commonly prescribed as CNS stimulants for managing ADHD. In an educational context, it is important for healthcare professionals to understand the pharmacological treatment options for ADHD to provide safe and effective care to patients. By knowing the appropriate medications and their mechanisms of action, healthcare providers can make informed decisions when managing ADHD and advocate for the best outcomes for their patients.