Terbutaline (Brethine) is one of the most frequently used drugs in the treatment of preterm labor. A new form of giving terbutaline, the continuous subcutaneous infusion pump, allows terbutaline to be easily given around the clock without the need for an IV. There are, however, disadvantages: the pump is expensive and is more invasive than the oral or subcutaneous route. Now even more seriously, the FDA has warned that terbutaline administered by injection or through such a pump should not be used in pregnant women for prevention or prolonged treatment of preterm labor due to the potential for serious maternal heart problems and death.
Terbutaline is derived from a hormone called epinephrine, which is released when a woman is under stress, a response that’s commonly called the “fight or flight” response. Stress causes many of the muscles in a woman’s body to contract, so that she is ready to respond quickly. One type of muscle in the body (smooth muscle) however, relaxes when a woman is under stress. Since most of the uterus is made up of smooth muscle, the uterus will relax in response to a drug that contains substances like epinephrine.
Terbutaline is a bronchodilator, a medication that dilates (expands) air passages in the lungs. It attaches to beta adrenergic receptors on muscles surrounding the air passages, causing the muscles to relax and dilate the air passages. Wider air passages allow more air to flow in and out of the lungs. Increased airflow reduces shortness of breath, wheezing, and cough.
The drug is currently on the World Anti-Doping Agency’s list of prohibited drugs for Olympic athletes, except when administered by inhalation and a Therapeutic Use Exemption (TUE) has been obtained in advance.
Women respond differently to terbutaline, so its effects and how long they last vary from woman to woman. When a woman has a good response, terbutaline reduces the number and frequency of contractions. And yet, like all tocolytic drugs, terbutaline has not been shown to consistently prevent or delay preterm delivery for a significant period of time.
Even so, studies have shown that terbutaline can usually delay delivery for at least several days (depending on how much a woman’s cervix is dilated before beginning medication). This isn’t a lot of time, but it can make a big difference for the fetus if the mother is given steroids along with terbutaline. After 48 hours, steroids improve a baby’s lung function and reduce his or her risk of dying by 40%.
The FDA is now stating that oral terbutaline tablets should not be used for prevention or treatment of preterm labor. The FDA is requiring the addition of a Boxed Warning and Contraindication to the drug prescribing information (labeling) to warn against these uses.
Scott Monroe, M.D., director of FDA’s Division of Reproductive and Urologic Products states:
“Women should be aware that serious and sometimes fatal side effects have been reported after prolonged use of terbutaline in pregnant women. It is important for patients and health care professionals to consider all the potential risks and known benefits of any drug before deciding on its use.”
FDA warning relates to safety concerns about the prolonged use of terbutaline injection beyond 48-72 hours, and against any use of oral terbutaline in pregnant women for prevention or treatment of preterm labor.
The FDA’s reviewed cases of heart problems and even death associated with terbutaline use for obstetric indications, as well as data from medical literature documenting the lack of safety and effectiveness of terbutaline for preventing preterm labor. It has been concluded that the risk of serious adverse events outweighs any potential benefit to pregnant patients for either prolonged use of terbutaline injection beyond 48-72 hours or use of oral terbutaline for prevention or treatment of preterm labor.
Written by Sy Kraft, B.A.