A 44-year-old man with newly diagnosed atrial fibrillation starts flecainide 100 mg twice daily. His physician explains that reaching steady state requires approximately 5 half-lives, noting that flecainide has a volume of distribution of roughly 8–10 L/kg and undergoes hepatic metabolism with renal excretion. Vital signs: BP 138/82, HR 102, RR 16, Temp 37°C, SpO2 98%. ECG shows prolonged QRS duration. Creatinine clearance is 85 mL/min. The patient, currently taking no other medications, asks which factors primarily determine this drug's half-life. Which of the following best answers his question?
- A)It increases with greater potency and decreases with lower efficacy
- B)It is unrelated to renal or hepatic dysfunction
- C)It is determined only by receptor affinity
- D)It increases with larger volume of distribution and decreases with higher clearanceGABARITO
- E)It depends only on hepatic first-pass metabolism
Explicação
Half-life is proportional to volume of distribution and inversely proportional to clearance. Drugs that distribute widely into tissues take longer to clear from the body, whereas drugs with high renal or hepatic clearance have shorter half-lives. This is why o... Ver explicação completa e trilha adaptativa →