Root Cause Analysis Practice Test

A 24-year-old woman (52 kg) presents to urgent care with tremor, palpitations, and insomnia that started after she began an OTC product for weight loss. Current medications: levothyroxine 88 mcg PO daily (stable), ethinyl estradiol/levonorgestrel 1 tablet PO daily, and a new OTC “energy/weight loss” supplement containing high-dose caffeine and yohimbine; no recent prescription changes. Labs: TSH 2.1 mIU/L (WNL), HR 118 bpm; allergies: none; PMH: hypothyroidism; no hospitalizations. What is the most likely cause of this patient's symptoms?

A 29-year-old female (64 kg) presents to the pharmacy reporting persistent vaginal itching and thick discharge despite using fluconazole. Medical history: recurrent vulvovaginal candidiasis; allergy: none; not pregnant. Medications: fluconazole 150 mg PO once (taken 3 days ago), combined oral contraceptive daily, and she recently started rifampin 600 mg PO daily 2 weeks ago for latent tuberculosis infection. Labs: AST/ALT WNL, SCr 0.7 mg/dL; no recent hospitalizations. Which factor is contributing to the therapeutic failure?