METHOTRIMEPRAZINE

Fetal Risk Summary

Methotrimeprazine, a propylamino phenothiazine in the same class as chlorpromazine, is used primarily as a sedative and analgesic. Although specific data are not available, other phenothiazines readily cross the placenta, and methotrimeprazine should be expected to enter the fetus.

Methotrimeprazine has been used for obstetric analgesia (1,2). The drug does not affect the force, duration, and frequency of uterine contractions, nor does it affect fetal heart tones (1,2). The manufacturer, however, has unsubstantiated data on file that methotrimeprazine may increase the rate of cervical dilation (2). No adverse effects were observed in more than 800 newborns exposed to the drug during labor (2).

In a prospective study that compared 315 women consuming phenothiazines during the 1st trimester with 11,099 nonexposed controls, malformations were observed in 11 exposed infants (3.5%) vs. 178 controls (1.6%) (p<0.01) (3). In the phenothiazine group, methotrimeprazine was taken by 18 women, 2 of whom delivered children with defects, 1 with hydrocephalus and 1 with a cardiac malformation (type not specified).

A cause-and-effect relationship between methotrimeprazine and the defects cannot be determined from this study. However, other phenothiazines are generally considered safe for both mother and fetus if used occasionally in low doses (e.g., see Chlorpromazine), and methotrimeprazine can probably be classified similarly. Other reviewers have also concluded that the phenothiazines are not teratogenic (4,5).

Breast Feeding Summary

No data are available.

References

1. DeKornfeld TJ, Pearson JW, Lasagna L. Methotrimeprazine in the treatment of labor pain. N Engl J Med 1964;270:391–4.
2. Levoprome: methotrimeprazine parenteral. Lederle Laboratories, December 1966:15.
3. Rumeau-Rouquette C, Goujard J, Huel G. Possible teratogenic effect of phenothiazines in human beings. Teratology 1976;15:57–64.
4. Ayd FJ Jr. Children born of mothers treated with chlorpromazine during pregnancy. Clin Med 1964;71:1758–63.
5. Ananth J. Congenital malformations with psychopharmacologic agents. Compr Psychiatry 1975;16:437–45.