The full, clinically endorsed recommendation should be obtained from Lareb. 

Rationale for drug selection 

Nifedipine is a calcium channel blocker used in pregnancy for hypertension and as a tocolytic. It is known that pregnancy alters pharmacokinetics of drugs. Therefore, dose adjustments might be needed to sustain blood pressure control.

Pharmacokinetics of nifedipine in pregnancy 

Nifedipine undergoes hepatic metabolism via CYP3A4. Pregnancy increases CYP3A4 activity and hepatic blood flow, leading to higher clearance. Particularly in the second and third trimester, a decrease of maternal nifedipine concentrations is observed. Peak levels may be 50% lower compared to non‑pregnant individuals. Interindividual variability is large, therefore on an individual basis, it may be considered to increase the dosage of nifedipine. Nifedipine crosses the placenta, exposing the foetus about 78% of the maternal concentration.

Benefits and risk with proposed dose adjustments 

The expected benefits and associated risk of increasing the nifedipine dose during pregnancy.

In short 

Pregnancy increases nifedipine clearance and lowers exposure. On an individual basis, it may be considered to increase the dosage of nifedipine to maintain blood pressure control in pregnancy. Based on the weighing of benefits and risks, the working committee derived an appropriate dose adjustment. Consult Lareb for the model-informed dosing recommendations.