Respiratory Drug (Bronchodilator)
PREGNANCY RECOMMENDATION: No Human Data—Probably Compatible
BREASTFEEDING RECOMMENDATION: No Human Data—Probably Compatible
PREGNANCY SUMMARY
No reports describing the use of pirbuterol in human pregnancy have been located. The animal reproduction data suggest low risk. Other agents in this class (see below) are considered low risk or compatible. Because of its β-2 adrenergic activity, the drug probably inhibits uterine contractions. However, this effect is not seen clinically because the drug has not been detected in blood after inhalation. Nevertheless, pirbuterol inhalers should only be used during labor if clearly indicated. If pirbuterol is used in pregnancy for the treatment of asthma, health care professionals are encouraged to call the toll-free number 877-311-8972 for information about patient enrollment in an Organization of Teratology Information Specialists (OTIS) study.
FETAL RISK SUMMARY
Pirbuterol is an inhaled sympathomimetic amine that has a preferential effect on β-2 adrenergic receptors (1). Other agents in this class are albuterol, metaproterenol, salmeterol, and terbutaline. Pirbuterol is indicated for the prevention and reversal of bronchospasm in patients ≥12 years of age with reversible bronchospasm including asthma. It may be used with or without concurrent theophylline and/or corticosteroid therapy. Each activation delivers a total dose of 453 mcg of pirbuterol acetate. Systemic blood concentrations of pirbuterol following inhalation of doses up to 800 mcg were below the level of detection (2–5 ng/mL). When the drug was given orally, the plasma elimination half-life was about 2 hours (1).
Reproduction studies have been conducted in rats and rabbits. In rats, no teratogenicity was observed with oral doses up to 1000 times the maximum recommended daily inhalation dose in adults based on BSA (MRDID). Pirbuterol was not teratogenic in rabbits given oral doses up to 680 times the MRDID. At 2000 times the MRDID, abortions and fetal death were observed in rabbits (1).
In long-term studies with rats and mice, no evidence of carcinogenicity was seen with dietary doses up to 35 and 15 times the MRDID, respectively. Assays for mutagenicity and cytogenicity were negative. There also was no evidence of impaired fertility in rats given oral doses up to 35 times the MRDID (1).
It is not known if pirbuterol crosses the human placenta. Although the molecular weight (about 300) is low enough, the drug has not been detected in blood when administered by inhalation.
BREASTFEEDING SUMMARY
No reports describing the use of pirbuterol inhalers during human lactation have been located. Although the molecular weight (about 300) is low enough, the drug has not been detected in blood when administered by inhalation. Consequently, there should be no drug in breast milk.
Reference
1.Product information. Maxair. Graceway Pharmaceuticals, 2009.