Amlodipine Should Be Dosed Once Daily, Not Twice Daily
Amlodipine should be administered once daily, not twice daily, due to its long half-life of 40-60 hours which provides complete 24-hour blood pressure control with a single dose. 1, 2, 3
Pharmacokinetic Properties Supporting Once-Daily Dosing
- Amlodipine has a prolonged elimination half-life (40-60 hours) that allows for consistent blood pressure control over a full 24-hour period 3
- The drug reaches steady state within 1-1.5 weeks of daily administration 1
- Plasma concentration fluctuation between doses is minimal (20-25%) with once-daily dosing 3
- High oral bioavailability (60-80%) contributes to reliable drug levels 1
Official Dosing Recommendations
The FDA-approved dosing for amlodipine is explicitly stated as once daily:
- Initial dose for adults: 5 mg once daily 2
- Maximum dose for adults: 10 mg once daily 2
- For elderly, fragile patients or those with hepatic insufficiency: 2.5 mg once daily 2
- For children 6-17 years: 2.5-5 mg once daily 2
Clinical Evidence Supporting Once-Daily Dosing
Research confirms that once-daily dosing provides effective 24-hour blood pressure control:
- 24-hour intra-arterial blood pressure monitoring demonstrates that once-daily amlodipine effectively reduces blood pressure throughout the entire day without altering normal circadian patterns 4
- Mean daytime blood pressure reductions from 165/103 to 147/89 mmHg and nighttime reductions from 137/79 to 121/69 mmHg have been documented with once-daily dosing 4
- Studies show significant reductions in blood pressure (23/13 mmHg supine, 24/12 mmHg standing) 24 hours after the last dose 1
Patient Compliance Considerations
- Patient compliance is significantly better with once-daily dosing compared to multiple daily doses 5
- Once-daily dosing provides superior therapeutic coverage compared to twice-daily regimens 5
Potential Pitfalls of Twice-Daily Dosing
- Splitting the dose could potentially lead to:
- Unnecessary fluctuations in drug levels
- Reduced patient adherence
- Increased risk of adverse effects due to higher peak concentrations
- No additional therapeutic benefit
Dose Titration Approach
When adjusting amlodipine dosage:
- Wait 7-14 days between titration steps to assess full effect 2
- Consider that maximum effect may not be seen until 6 weeks of treatment 6
- If blood pressure control is inadequate after appropriate waiting period, increase to maximum dose of 10 mg once daily rather than splitting the dose 2
In conclusion, based on amlodipine's pharmacokinetic profile, FDA labeling, and clinical evidence, there is no therapeutic advantage to dividing the dose into twice-daily administration. The drug's long half-life specifically enables effective once-daily dosing, which also promotes better patient adherence.