Risk Factor: C
Class: Central nervous system drugs/ Tranquilizers
Fetal Risk Summary
Thioridazine is a piperidyl phenothiazine. The drug is not teratogenic in animals (species not specified) (1).
The phenothiazines readily cross the placenta (2). Extrapyramidal symptoms were seen in a newborn exposed to thioridazine in utero, but the reaction was probably caused by chlorpromazine (3).
In a surveillance study of Michigan Medicaid recipients involving 229,101 completed pregnancies conducted between 1985 and 1992, 63 newborns had been exposed to thioridazine during the 1st trimester (F. Rosa, personal communication, FDA, 1993). Two (3.2%) major birth defects were observed (three expected), one of which was a cardiovascular defect (one expected). No anomalies were observed in five other categories of defects (oral clefts, spina bifida, polydactyly, limb-reduction defects, and hypospadias) for which specific data were available.
A case of a congenital heart defect was described in 1969 (4). However, one investigator found no anomalies in the offspring of 23 patients exposed throughout gestation to thioridazine (5). Twenty of the infants were evaluated for up to 13 years. Although occasional reports have attempted to link various phenothiazine compounds with congenital malformations, the bulk of the evidence indicates that these drugs are safe for the mother and fetus (see Chlorpromazine).
Breast Feeding Summary
No data are available.
- Product information. Mellaril. Sandoz Pharmaceutical Corporation, 1993.
- Moya F, Thorndike V. Passage of drugs across the placenta. Am J Obstet Gynecol 1962;84:177898.
- Hill RM, Desmond MM, Kay JL. Extrapyramidal dysfunction in an infant of a schizophrenic mother. J Pediatr 1966;69:58995.
- Vince DJ. Congenital malformations following phenothiazine administration during pregnancy. Can Med Assoc J 1969;100:223.
- Scanlan FJ. The use of thioridazine (Mellaril) during the first trimester. Med J Aust 1972;1:12712.