Premature labor and preterm birth may have considerable negative health impacts on the baby and the mother. Tocolytics are a category of medications used to suppress uterine contractions and deter labor onset. The use of tocolytics such as Nifedipine in pregnancy is one of the ten recommendations of the World Health Organization (WHO) to prevent preterm birth and support the premature baby’s survival (1). Read this post to know about the safety of using Nifedipine during pregnancy, when and how to use it, and its potential side effects.
What Is Nifedipine?
Nifedipine (sold under the brand names Procardia, Adalat,) is a calcium ion influx inhibitor which helps in managing hypertension, vasospastic angina (spasms in the coronary heart), and chronic stable angina (2). This drug is also used to suppress preterm labor and delay delivery (3).
Is It Safe To Use Nifedipine During Pregnancy?
It is both yes and no, read on to find out more.
The US Food and Drug Administration (FDA) categorized nifedipine as “pregnancy category C” drug, which means animal studies have shown some adverse effects, and there are no well-controlled studies in humans. It recommends the use of nifedipine only if the potential benefits outweighs its risks (2).
Also, the usage of this drug depends on why it is considered in the first place during pregnancy. Next, we take a look at such scenarios.
What Is Nifedipine Used For During Pregnancy?
There are two cases during pregnancy where your doctor could prescribe nifedipine. Do not take this medicine without consulting a doctor.
A descriptive study of 21 pregnant women with acute episodes of severe hypertension during pregnancy when given nifedipine showed a significant fall of blood pressure. Even though there were side effects such as headache and cutaneous flushing, no adverse fetal defects were seen (4).
The WHO guideline development group agreed that “in women at risk of imminent preterm birth, who have an otherwise uncomplicated pregnancy, the acute use of a tocolytic drug to prolong the pregnancy to up to 48 hours can be considered as a window for administration of antenatal corticosteroids” (1).
Nifedipine is considered the preferred tocolytic agent to others. Your doctor might prescribe this medication for prolonging the pregnancy for as long as it is safe to do, if it helps in improving the neonatal outcome.
How Does Nifedipine Work During Pregnancy?
Nifedipine helps in short-term prolongation of pregnancy by relaxing the smooth muscles and inhibiting contraction of the uterine wall. The main advantage of this drug is to prolong the delivery by 48 hours such that it gives time for the corticosteroids to accelerate the lung formation of the baby. Nifedipine is given between 24 and 34 weeks of gestation with intact membranes in an otherwise uncomplicated pregnancy (5).
When Is Nifedipine Not Used As A Tocolytic Agent?
While nifedipine is considered safer than other tocolytic agents, doctors do not prescribe this drug in certain cases. The WHO contraindicates the usage of nifedipine for tocolysis if the mother has the following conditions (1).
- Preterm pre-labor rupture of membranes
- Chorioamnionitis (a bacterial infection before or during the labor)
- Placental abruption
- Cardiac disease
What Is The Recommended Dosage Of Nifedipine During Pregnancy?
Once there is confirmation of preterm labor, a stat dose of 20mg is usually given. If the contractions do not settle, your doctor might give a second dose of 20mg 30 minutes after the first dose. No further medicine is given until three hours after the second dose (6).
If the contractions continue even after that, then another 20mg of nifedipine is given every three to six hours for 48 hours until the contractions stop.
The doctors usually do not give more than 160mg within 24 hours.
What Are The Side Effects Of Nifedipine During Pregnancy?
A study on 70 consecutive women with clinical features of preterm labor concluded that nifedipine was more successful in prolongation of the pregnancy with fewer side effects and better tolerability (7).
Although calcium channel blockers such as nifedipine are generally well tolerated, they are associated with a few side effects such as (8).
- Headache associated with transient hypotension
- Maternal tachycardia
- Palpitations and flushing
- Maternal pulmonary edema (when given orally)
- Difficulty in breathing
Does Nifedipine Affect The Fetus?
A retrospective analytical study of 4,478 uncomplicated pregnancies, which were treated with nifedipine for preterm delivery, resulted in an overall success rate of 84.92% with no major maternal and fetal side effects (9).
How Long Does Nifedipine Work For Preterm Labor?
A tocolytic agent such as nifedipine can delay the labor for over 48 hours (1). In a randomized study with 206 threatened preterm labor patients, after 90 minutes of administration of nifedipine, 88.3% women of the nifedipine group had no uterine contractions (10).
There is a chance that drugs like nifedipine can help in better neonatal outcome in risky pregnancies. The doctors prescribe such medications only when the need outweighs the risks.
Precaution: Consumption of grapefruit as a whole or its juice must be avoided while taking nifedipine, because the chemicals in the fruit bind with the medicine and reduce its absorption through the gut. Thus, high concentrations of the medicine can enter directly into your bloodstream, causing an overdose (11).
Due to its categorization as a “pregnancy category C” drug, Nifedipine in pregnancy can be taken if its benefits outweigh its risks. Your doctor may prescribe this drug either as a tocolytic agent to avoid preterm delivery and maintain the premature baby’s survival or to maintain optimal blood pressure in the case of severe hypertension in expectant mothers. While the risk of serious fetal abnormalities from Nifedipine is low, it can produce side effects such as maternal tachycardia, anxiety, and maternal pulmonary edema. So, only take Nifedipine if your doctor has recommended it, and avoid eating grapefruit while taking it.
2. Procardia XL; The US Food and Drug Administration
3. Patricia Smith, John Anthony, Richard Johanson; Nifedipine in pregnancy; British Journal of Obstetrics and Gynaecology
4. Walters and Redman; Treatment of severe pregnancy‐associated hypertension with the calcium antagonist nifedipine; BJOG
5. Protocol: Tocolysis with Nifedipine; Cree Health
6. Nifrdipine for preterm labour; South Australian Perinatal Practice Guideline; Department for Health and Agening, Government of South Australia
7. Maitra Nandita, Christian Vincent, Verma RN, Desai VA; Maternal and fetal cardiovascular side effects of nifedipine and ritodrine used as tocolytics; The Journal of Obstetrics and Gynecology of India
8. Robert Gaspar; and Judit Hajagos; Calcium Channel Blockers as Tocolytics: Principles of Their Actions, Adverse Effects and Therapeutic Combinations; NCBI (2013)
9. Parag Hangekar, Anand Karale, and Neelesh Risbud; Our experience of nifedipine as a tocolytic agent in preterm labor (24 weeks to 36 weeks 6 days); International Journal of Reproduction, Contraception, Obstetrics and Gynecology
10. Srisuda Songthamwat, Chatchanawadee Na Nan, and Metha Songthamwat; Effectiveness of nifedipine in threatened preterm labor: a randomized trial; NCBI(2018)
11. Grapefruit and medication: A cautionary note; Harvard Health Publishing