No, amlodipine should not be dosed at 5 mg twice daily
Amlodipine is specifically designed and FDA-approved for once-daily dosing only, with a maximum dose of 10 mg given as a single daily dose, not divided. 1
Pharmacologic Rationale
Amlodipine has unique pharmacokinetic properties that make twice-daily dosing unnecessary and inappropriate:
- Half-life of 35-50 hours - This exceptionally long half-life ensures sustained drug levels well beyond 24 hours 2
- Duration of action exceeds 24 hours - Blood pressure control is maintained even if a dose is missed 2
- Low renal clearance (7 mL/min/mg) - Results in prolonged drug retention 2
Evidence Against BID Dosing
Research directly examining divided dosing demonstrates no clinical benefit:
A crossover study comparing amlodipine 10 mg once daily versus 5 mg twice daily found 3:
- No significant difference in 24-hour blood pressure control (129.7/80.1 vs 130.5/80.1 mm Hg)
- No difference in daytime, nighttime, or early morning blood pressure
- No difference in trough plasma concentrations (22.37 vs 20.57 ng/mL)
- No reduction in arterial stiffness with divided dosing
Animal studies similarly showed that twice-daily dosing created a bimodal blood pressure pattern without improving overall control 4.
Guideline-Recommended Dosing
All major guidelines consistently specify once-daily dosing 5, 6, 7, 8, 9, 10:
Adults:
- Starting dose: 2.5-5 mg once daily
- Maximum dose: 10 mg once daily
- Titration interval: 7-14 days between dose adjustments 1
Pediatrics (ages 6-17):
Special populations:
- Elderly, frail, or hepatic insufficiency: Start at 2.5 mg once daily 1
Common Pitfalls to Avoid
- Do not split the daily dose - There is no pharmacologic or clinical rationale for BID dosing
- Do not exceed 10 mg total daily dose in adults or 5 mg in children - Higher doses increase side effects (particularly edema) without proportional benefit 2
- Timing flexibility - Patients should take amlodipine at the most convenient time to establish a habitual pattern and improve adherence 10
When to Consider Alternatives
If blood pressure remains uncontrolled on amlodipine 10 mg once daily:
- Add a second agent (ACE inhibitor/ARB or thiazide diuretic) rather than dividing the amlodipine dose 7, 10
- Consider single-pill combination therapy to improve adherence 10
- Evaluate for secondary hypertension or medication non-adherence
The correct approach is to optimize once-daily dosing (up to 10 mg) and add complementary agents from different classes, not to divide amlodipine into twice-daily administration.