Which of the following is the most common presenting sign of substance abuse in adolescents?

Correct Answer: D

Rationale: The correct answer is D: Changes in behavior. This is the most common presenting sign of substance abuse in adolescents because substance use often leads to noticeable changes in behavior, such as irritability, mood swings, aggression, and withdrawal from family and friends. These behavioral changes are typically the first noticeable signs of substance abuse. A: Poor school performance may be a consequence of substance abuse, but it is not necessarily the most common presenting sign. B: Change in sleep habits can be a sign of substance abuse, but changes in behavior are more prominent and common. C: Increased blood pressure is a physical symptom of substance abuse, but changes in behavior are usually more readily apparent and commonly observed in adolescents with substance abuse issues.

Correct Answer: A

Rationale: Rationale for correct answer (A): Amoxicillin does not significantly interact with warfarin. It is an antibiotic that works through a different mechanism than warfarin and is not known to affect its anticoagulant activity. Summary of incorrect choices: B (Trimethoprim/sulfamethoxazole): This drug combination can enhance the effects of warfarin, increasing the risk of bleeding. C (Ciprofloxacin): Ciprofloxacin can increase warfarin's effects, leading to a higher risk of bleeding. D (Clarithromycin): Clarithromycin can interact with warfarin, potentially increasing the risk of bleeding.

Correct Answer: D

Rationale: The correct answer is D: A deviated septum. Unilateral rhinitis typically refers to inflammation in one nostril. A deviated septum is a physical obstruction in the nasal passage that affects both nostrils, not just one. Choices A, B, and C can all cause unilateral rhinitis as they specifically affect one side of the nasal passage. A foreign body in the nasal canal, a nasal polyp, and drug-induced rhinitis can all lead to inflammation and symptoms in one nostril.

Correct Answer: C

Rationale: The correct answer is C: Urinary tract infections. Prostatic hypertrophy can cause obstruction of the urinary tract, leading to urinary retention and stasis, which increases the risk of urinary tract infections. Constipation (choice A) and fecal incontinence (choice B) are more related to issues with the gastrointestinal system rather than prostatic hypertrophy. Prostate cancer (choice D) is a separate condition that is not directly linked to prostatic hypertrophy. Therefore, the increased risk for an 84-year-old male with prostatic hypertrophy is urinary tract infections due to urinary obstruction.

Correct Answer: A

Rationale: The correct answer is A: Aminoglycosides. Aminoglycosides can cause ototoxicity, resulting in decreased hearing. They are known to damage the sensory cells in the inner ear. Beta-lactams (B) and Cephalosporins (C) are not associated with hearing loss. Macrolides (D) can rarely cause hearing loss but are not as commonly linked to ototoxicity as aminoglycosides.