Side-effect and vital sign profile of nifedipine as a tocolytic for preterm labour

LW Chan, DS Sahota, SY Yeung, TY Leung, TY Fung, TK Lau, TN Leung
Fetal Medicine Unit, Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong

OBJECTIVE. To examine the side-effect and vital sign profile of nifedipine used as a tocolytic.

DESIGN. Retrospective audit.

SETTING. Tertiary care university hospital, Hong Kong.

PATIENTS. Women presenting with preterm labour (before 34 weeks of gestation) between March 2001 and September 2004.

MAIN OUTCOME MEASURES. Maternal heart rate, blood pressure, and foetal heart rate were monitored regularly. A four-point Likert scale multiple-choice questionnaire was used to assess the perceived degree of flushing, headache, nausea, dizziness, and shortness of breath. All assessments were performed at predefined intervals from the onset of treatment. Repeated measures analysis of variance was performed to identify any time-dependent association with nifedipine treatment.

RESULTS. In all, 212 episodes of preterm labour were treated with nifedipine in 203 women. In 120 episodes, preterm labour was suppressed for more than 48 hours. Treatment was discontinued in three women because of profound hypotension (<90/60 mm Hg), and in one because of severe flushing. Only one patient developed maternal tachycardia (≥140 beats per minute), and in two foetal tachycardia (≥180 beats per minute) was encountered. Moderate headache was experienced in nine women, flushing in nine, dizziness in four, nausea in three, and shortness of breath in one. Repeated measures analysis of variance with time of measurement revealed a significant reduction in maternal blood pressure and increase in maternal heart rate that plateaued after 1 hour of therapy. The foetal heart rate returned to baseline values 3 hours after commencing therapy.

CONCLUSION. In general, use of nifedipine as the first-line tocolytic was safe. However, severe maternal hypotension can occur and close monitoring of vital signs is warranted.

Hong Kong Med J 2008;14:267-72

Key words: Nifedipine; Obstetric labor, Premature; Tocolysis