From the Guidelines
To convert from Nifedipine ER 30 mg daily to regular Nifedipine, the patient should take 10 mg of regular Nifedipine three times daily, as this maintains the same total daily dose of 30 mg but accounts for the different release mechanisms 1.
Key Considerations
- The immediate-release formulation should be taken approximately 8 hours apart (e.g., 8 AM, 4 PM, and midnight) to maintain consistent blood levels throughout the day.
- Patients should be monitored for potential side effects like headache, flushing, dizziness, or rapid heart rate, which may be more pronounced with immediate-release formulations due to faster absorption and higher peak concentrations.
- The extended-release formulation provides more consistent blood levels over 24 hours, while the immediate-release version has more rapid onset but shorter duration of action (4-8 hours) 1.
Important Guidance
- Immediate-release nifedipine is not recommended for UA/NSTEMI except with concomitant beta blockade 1.
- Patients should be advised not to crush or chew the immediate-release capsules and to take them consistently with respect to meals, as food can affect absorption.
- The properties of calcium channel blockers, including nifedipine, are outlined in Table 16 of the guidelines, which provides information on usual dose, duration of action, and side effects 1.
Clinical Implications
- The conversion from extended-release to immediate-release nifedipine is necessary because the pharmacokinetic profiles differ significantly between formulations.
- Clinicians should be aware of the potential risks and benefits of using calcium channel blockers in patients with unstable angina or non-ST-elevation myocardial infarction, and should carefully consider the choice of agent and dosing regimen in individual patients 1.
From the FDA Drug Label
When nifedipine extended-release tablets are administered as multiples of 30 mg tablets over a dose range of 30 mg to 90 mg, the area under the curve (AUC) is dose proportional; however, the peak plasma concentration for the 90 mg dose given as 3 x 30 mg is 29% greater than predicted from the 30 mg and 60 mg doses Two 30 mg nifedipine extended-release tablets may be interchanged with a 60 mg nifedipine extended-release tablet. The bioavailability of nifedipine from nifedipine extended-release tablets relative to immediate release tablets is in the range of 84%-89%.
To convert Nifedipine ER 30 mg daily to regular Nifedipine, consider the following:
- The bioavailability of nifedipine from extended-release tablets is 84%-89% relative to immediate release tablets.
- The peak plasma concentration and area under the curve (AUC) may vary between extended-release and immediate release formulations.
- No direct conversion is provided in the label, but considering the bioavailability, the dose of regular Nifedipine may need to be adjusted to achieve the same therapeutic effect as Nifedipine ER 30 mg.
- It is recommended to consult the prescriber or a pharmacist to determine the appropriate dose of regular Nifedipine based on the individual patient's needs and response to the medication 2.
From the Research
Conversion of Nifedipine ER 30 mg daily to regular Nifedipine
- The conversion of Nifedipine ER 30 mg daily to regular Nifedipine is not directly addressed in the provided studies, as they focus on comparisons between different formulations of Nifedipine and other calcium channel blockers like Amlodipine 3, 4, 5, 6, 7.
- However, a study comparing the efficacy of two long-acting formulations of Nifedipine (PA tablet bid and GITS tablet once daily) found that patients whose hypertension is controlled by Nifedipine-PA 10 or 20 mg bid can be successfully converted to Nifedipine-GITS with most patients remaining normotensive on 30 mg daily 5.
- Another study evaluated the appropriate dosing of Amlodipine when converting patients from Nifedipine ER to Amlodipine, suggesting that an initial Amlodipine dose of 5 or 10 mg once daily can be used, with dosage titration required in some patients to obtain adequate control of blood pressure 4.
- A comparison between Nifedipine and Amlodipine for the treatment of essential hypertension found that Amlodipine given once daily is at least as effective as Nifedipine tablets given twice daily 6.
- A literature review comparing Amlodipine and Nifedipine GITS found that both drugs lower blood pressure effectively with minimal effects on heart rate, but with small differences in the extent to which each activates the sympathetic nervous system 7.