Therapeutic drug monitoring on the use of transplacental digoxin in fetal tachyarrhythmia: a case report

Abstract

Fetal tachycardia (FT) is a rare disorder and is associated with significant mortality of fetus. Digoxin is one of the antiarrhythmic agents used to treat FT via transplacental therapy. In this report, we describe a therapeutic drug monitoring (TDM) case of digoxin during the treatment of FT. A 40-year-old woman, gravida 2 para 1, hospitalized to control FT as the fetal heart rate (FHR) showed over 200 bpm on ultrasonography at 29 weeks of gestation. She did not have any medical or medication history and showed normal electrolytes level on clinical laboratory test results. For the treatment of FT loading and maintenance dose of intravenous digoxin (loading dose: 0.6 mg; maintenance dose: 0.3 mg every 8 hours) were administered. To monitor the efficacy and safety of the treatment, TDM was conducted with a target maternal serum trough digoxin concentration of 1.0 to 2.0 ng/mL, as well as ultrasonography and maternal electrocardiogram. The observed digoxin serum concentrations were 0.67, 0.83, and 1.05 ng/mL after 1, 2, and 5 days after the initiation of digoxin therapy, respectively. Although the serum digoxin concentrations reached the target range, the FHR did not improve. Therefore, digoxin was discontinued, and oral flecainide therapy was started. The FHR adjusted to the normal range within 2 days from changing treatment and remained stable. TDM of digoxin along with the monitoring of clinical responses can give valuable information for decision-making during the treatment FT.

Supraventricular Tachycardia Associated With Repeat Cesarean Section Under Spinal Anesthesia

“…Tight monitoring of serum digoxin levels is required due to the narrow therapeutic window. Vomiting should be considered an early sign of toxicity, but other possible side effects may include nausea, diarrhea, blurry vision, and fetal complications such as fetal arrhythmias [10,11]. In patients where no pharmacologic agents are useful in the termination of the SVT and if they start to become unstable, synchronized cardioversion has been shown to be safe and efficacious throughout pregnancy.…”