Nifedipine In Pregnancy: Safety, Usage, Dosage And Side Effects

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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 and is used as an antihypertensive medication, which helps in managing hypertension, vasospastic angina (spasms in the coronary heart), and chronic stable anginaⁱChest pain that frequently happens with action or under emotional stress. (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 outweigh its risks, such as to reduce maternal and fetal distress (2).

Also, the usage of this antihypertensive 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.

1. Hypertension

The overall prevalence of hypertensive disorders of pregnancy during 2017-2019 was 14.6%, as per the CDC. A descriptive study of 21 pregnant women with acute episodes of severe maternal blood pressure during pregnancy showed a significant fall when given nifedipine. Even though there were side effects such as headache and cutaneous flushing, no adverse fetal defects were seen (4).

2. Tocolysis

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 corticosteroidsⁱDrugs that are given to expectant mothers to prevent premature birth. ” (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 the short-term prolongation of pregnancy by relaxing the smooth muscles and inhibiting the 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 corticosteroidsi 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. It is usually administered under medical supervision with close monitoring, especially during the first doses, to check its effectiveness and side effects. Dosages are adjusted based on the mother’s response and fetal condition (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 membranesⁱA membrane breakage that occurs before the labour contractions and prior to 37 weeks of pregnancy.
• Chorioamnionitis (a bacterial infection before or during the labor)
• Placental abruptionⁱThe early detachment of placenta from the uterine lining before the second stage of labour ends.
• 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 hypotensionⁱTemporary or short-term drop in blood pressure.
• Maternal tachycardiaⁱIncreased heart rate during pregnancy.
• Anxiety
• Vomiting
• Palpitations and flushing
• Maternal pulmonary edema (when given orally)ⁱThe buildup of fluid in the lungs during pregnancy.
• Difficulty in breathing

Does Nifedipine Affect The Fetus?

Studies show that nifedipine does not affect fetal movements, heart rate, or blood flow, so the probability of adverse defects, such as fetal heart rate abnormalities, is low when used as a tocolytic agent (8).

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 outcomes 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).

Illustration: Nifedipine In Pregnancy: Safety Usage Dosage And Side Effects

Are you wondering about the safety of blood pressure medications for you and your baby? The following video may provide you with more information on this question.

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