Maternal use of cyclobenzaprine (Flexeril) may induce ductal closure and persistent pulmonary hypertension in neonates

A full-term male infant presented shortly after birth with respiratory distress. An echocardiogram done within the first hour of life showed an elevated pulmonary artery pressure, an associated right ventricular hypertrophy without a patent ductus arteriosus. The patient was treated for persistent pulmonary hypertension with favorable response. Maternal history was unremarkable except for chronic low back pain treated with cyclobenzaprine (Flexeril®). A proposed mechanism for cyclobenzaprine includes inhibition of norepinephrine and serotonin reuptake, factors known to inhibit prostaglandin and nitric oxide. These two factors are the leading causes of in-utero ductal closure. This report is the first to indicate that cyclobenzaprine use during late pregnancy should be considered a potential cause of early ductal closure.