Uses and safety of acyclovir in pregnancy

Journal of Family Practice, Feb, 1994 by John G. Spangler, Julienne K. Kirk, Mark P. Knudson

Problematic Uses

Other uses of acyclovir in pregnancy remain problematic. Ciraru-Vigneron and colleagues[41] reported treating 9 women with acyclovir after 36 weeks' gestation to suppress symptomatic recurrences of genital herpes in an attempt to avoid cesarean section because of its associated maternal morbidity. While this approach seems reasonable, it is not known if acyclovir suppresses genital viral shedding during pregnancy or simply causes symptomatic lesions to become asymptomatic and undetectable.[6]

It is also unclear whether acyclovir should be used in mild or early cases of primary genital HSV infections.[6] Since patients with first-episode genital HSV infections (ie, those who previously have had HSV-1 or HSV-2 infections at another bodily site) are at no greater risk for dissemination than are women with recurrent genital herpes, they need not be treated with acyclovir.[20]

Although the use of acyclovir in ophthalmic zoster has not been specifically addressed, considering the guidelines reported for severe maternal varicella-zoster disease, "it would seem reasonable to make decisions about therapy [for ophthalmic zoster] on a case-by-case basis, evaluating such factors as the severity of the disease and the initial ophthalmologic findings."[42]

Conclusions

In this paper, we reported a case of first-trimester exposure to the antiviral drug acyclovir, highlighting the emotional impact of the exposure on the mother. We also have reviewed reports of its use during pregnancy and in situations where its gestational use appears justified. Limited data from clinical, laboratory, and animal studies show no consistent pattern of excessive maternal or fetal morbidity when acyclovir is used during pregnancy. However, since there have been relatively few reports of its use during all stages of pregnancy, it is difficult to draw firm conclusions regarding the effects on mother or fetus. The Acyclovir in Pregnancy Registry enables physicians to offer their patients more informed counsel about gestational exposure to the drug, which helps patients make rational decisions regarding their pregnancies.

Despite the potential risks, there are several circumstances in which the benefits of acyclovir therapy in pregnancy appear to outweigh possible fetal harm. These include severe, late-onset (eg, second or third trimester), or disseminated primary HSV infections and severe varicella-zoster infections, especially varicella pneumonia.

For severe HSV infections, one suggested regimen is intraveous acyclovir 7.5 mg/kg every 8 hours for a number of days, followed by oral acyclovir 200 mg every 4 hours to complete a 14-day course of antiviral therapy based on the rate of maternal improvement.[3] For severe varicella infections, 10 to 15 mg/kg intravenously every 8 hours for 7 days appears adequate.[28] Whenever acyclovir is used intravenously, the patient should be well hydrated with urine output maintained above 500 mL/h and serum BUN and creatinine levels closely monitored to avoid renal toxicity.[10,11]