From the FDA Drug Label
DOSAGE AND ADMINISTRATION Dosage must be adjusted according to each patient's needs. Therapy for either hypertension or angina should be initiated with 30 or 60 mg once daily. Angina patients controlled on nifedipine immediate-release capsules alone or in combination with other antianginal medications may be safely switched to nifedipine extended release tablets at the nearest equivalent total daily dose (e.g., 30 mg t.i. d. of nifedipine immediate-release capsules may be changed to 90 mg once daily of nifedipine extended release tablets).
The dosage of nifedipine long-acting 30mg three times a day (tid) is not recommended as the initial therapy, since the drug label recommends initiating therapy with 30 or 60 mg once daily. However, it is mentioned that angina patients controlled on nifedipine immediate-release capsules alone or in combination with other antianginal medications may be safely switched to nifedipine extended release tablets at the nearest equivalent total daily dose.
- The recommended equivalent total daily dose for 30mg tid of nifedipine immediate-release capsules is 90 mg once daily of nifedipine extended release tablets.
- Titration to doses above 120 mg are not recommended.
- Doses greater than 90 mg should be used with caution and only when clinically warranted 1.
From the Research
Nifedipine 30mg three times daily is not a safe or appropriate dosage for the long-acting formulation. Long-acting (extended-release) nifedipine is designed to be taken once daily, typically at doses of 30,60, or 90mg per day. Taking long-acting nifedipine three times daily would lead to drug accumulation and potentially dangerous hypotension, reflex tachycardia, dizziness, and other adverse effects. If this is indeed long-acting nifedipine (such as Procardia XL or Adalat CC), the correct dosing would be once daily, as supported by a study published in 2. The confusion may stem from immediate-release nifedipine, which is sometimes dosed multiple times per day, though 30mg three times daily would still be unusually high. Immediate-release nifedipine is now rarely used for hypertension due to concerns about rapid blood pressure drops, as noted in studies such as 3 and 4. If you're currently taking long-acting nifedipine three times daily, you should contact your healthcare provider immediately for dosage adjustment. Calcium channel blockers like nifedipine work by blocking calcium entry into vascular smooth muscle and cardiac cells, causing vasodilation and reducing blood pressure, but improper dosing can disrupt this mechanism and lead to serious side effects, as discussed in 5.
Some key points to consider:
- Long-acting nifedipine is designed for once-daily dosing
- Taking it three times daily can lead to adverse effects
- Immediate-release nifedipine has different dosing considerations
- Consult a healthcare provider for proper dosage adjustment
- Calcium channel blockers require careful dosing to avoid side effects
It's essential to follow the recommended dosing for long-acting nifedipine to minimize the risk of adverse effects and ensure the medication's efficacy in managing hypertension, as supported by the study in 2.