What medication should the nurse obtain a prescription for a client in labor who is HIV positive?

Zidovudine is the appropriate medication to obtain a prescription for a client in labor who is HIV positive. This antiretroviral medication is used to manage HIV infection and is critical during labor to reduce the risk of mother-to-child transmission of the virus. When administered intravenously during labor and continued postpartum for the newborn, Zidovudine has been shown to effectively decrease the viral load in the mother, thereby significantly reducing the likelihood of the infant acquiring HIV during delivery.

For a mother who is HIV positive, timely administration of Zidovudine is crucial as it plays a vital role in ensuring the health of both the mother and the newborn. It is a standard protocol in obstetric care for HIV-positive clients to minimize transmission risks.

The other medications listed serve different purposes: Valacyclovir is an antiviral used primarily for herpes viruses, Amphotericin B is an antifungal, and Metronidazole is an antibiotic that treats various infections. None of these would effectively manage HIV during labor or protect the infant from potential exposure to the virus in the same manner as Zidovudine.