CLONIDINE

Fetal Risk Summary

No reports linking the use of clonidine with congenital defects have been located. The drug has been used during all trimesters, but experience during the 1st trimester is very limited. Adverse fetal effects attributable to clonidine have not been observed (1,2,3,4,5,6,7 and 8).

Reproduction studies in rats at doses as low as 1/3 the oral maximum recommended daily human dose [MRDHD] on a weight basis (1/15 times the MRDHD on a mg/m2 basis), started before gestation, resulted in increased resorptions (9). Decreased embryo/fetal survival was not observed when these doses were used on gestation days 6–15, but did occur in both mice and rats at doses 40 times the MRDHD based on weight or 4 to 8 times the MRDHD based on surface area. No embryo or fetal toxicity or teratogenicity was observed in rabbits given doses up to 3 times the MRDHD (weight basis) (9).

In a surveillance study of Michigan Medicaid recipients involving 229,101 completed pregnancies conducted between 1985 and 1992, 59 newborns had been exposed to clonidine during the 1st trimester (F. Rosa, personal communication, FDA, 1993). Three (5.1%) major birth defects were observed (three expected), two of which were cardiovascular defects (0.6 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. The number of exposures is too small to draw any conclusions.

The pharmacokinetics of clonidine during pregnancy have been reported (10). The mean maternal and cord serum concentrations in 10 women were 0.46 and 0.41 ng/mL, respectively, corresponding to a cord:maternal ratio of 0.89. The mean amniotic fluid concentration was 1.50 ng/mL. The mean maternal dose was 330 µg/day. Results of neurologic examinations and limited blood chemistry tests in the exposed infants were similar to those in untreated controls. No neonatal hypotension was observed.

Breast Feeding Summary

Clonidine is secreted into breast milk (8,10). Following a 150-µg oral dose, milk concentrations of 1.5 ng/mL may be achieved (milk:plasma ratio 1.5) (P.A. Bowers, personal communication, Boehringer Ingelheim, Ltd., 1981). In a study of nine nursing women taking mean daily doses of 391.7 µg (postpartum days 1–5), 309.4 µg (postpartum days 10–14), and 241.7 µg (postpartum days 45–60), milk concentrations were approximately twice those in maternal serum (10). Mean milk levels were close to 2 ng/mL or higher during the three sampling periods. Hypotension was not observed in the nursing infants, although clonidine was found in the serum of the infants (mean levels less than maternal). The long-term significance of this exposure is not known.

References

1. Turnbull AC, Ahmed S. Catapres in the treatment of hypertension in pregnancy, a preliminary study. In Catapres in Hypertension. Symposium of the Royal College of Surgeons. London, 1970:237–45.
2. Johnston CI, Aickin DR. The control of high blood pressure during labour with clonidine. Med J Aust 1971;2:132.
3. Raftos J, Bauer GE, Lewis RG, Stokes GS, Mitchell AS, Young AA, Maclachlan I. Clonidine in the treatment of severe hypertension. Med J Aust 1973;1:786–93.
4. Horvath JS, Phippard A, Korda A, Henderson-Smart DJ, Child A, Tiller DJ. Clonidine hydrochloride a safe and effective antihypertensive agent in pregnancy. Obstet Gynecol 1985;66:634–8.
5. Horvath JS, Korda A, Child A, Henderson-Smart D, Phippard A, Duggin GC, Hall BM, Tiller DJ. Hypertension in pregnancy: a study of 142 women presenting before 32 weeks' gestation. Med J Aust 1985;143:19–21.
6. NG Wingtin L, Frelon JH, Beaute Y, Pellerin M, Guillaumin JP. Clonidine et traitement de l'hypertension arterielle de la femme enceinte. Cah Anesthesiol 1986;34:389–93.
7. Ng-Wing Tin L, Frelon JH, Beaute Y, Pellerin M, Guillaumin JP, Bazin C. Clonidine et traitement de l'hypertension arterielle de la femme enceinte. Rev Franc Gynecol Obstet 1986;81:563–6.
8. Wing-Tin LNG, Frelon JH, Hardy F, Bazin C. Clonidine et traitement des urgences hypertensives de la femme enceinte. Rev Franc Gynecol Obstet 1987;82:519–22.
9. Product information. Catapres. Boehringer Ingelheim Pharmaceuticals, 2000.
10. Hartikainen-Sorri A-L, Heikkinen JE, Koivisto M. Pharmacokinetics of clonidine during pregnancy and nursing. Obstet Gynecol 1987;69:598–600.