It has been shown in limited test studies that the nursing infant is exposed to approximately 0.3 mg/kg/day following oral administration of aciclovir to the mother. If nursing mothers have herpetic lesions near or on the breast, breast-feeding should be avoided. Adverse effects
Systemic therapy
Common adverse drug reactions (≥1% of patients) associated with systemic aciclovir therapy (oral or IV) include nausea, vomiting, diarrhea, encephalopathy (with IV use only), injection site reactions (with IV use only) and headache. In high doses, hallucinations have been reported. Infrequent adverse effects (0.1–1% of patients) include agitation, vertigo, confusion, dizziness, oedema, arthralgia, sore throat, constipation, abdominal pain, hair loss, rash and weakness. Rare adverse effects (<0.1% of patients) include coma, seizures, neutropenia, leukopenia, crystalluria, anorexia, fatigue, hepatitis, Stevens–Johnson syndrome, toxic epidermal necrolysis, thrombotic thrombocytopenic purpura and anaphylaxis.Intravenous aciclovir may cause reversible nephrotoxicity in up to 5% to 10% of patients because of precipitation of aciclovir crystals in the kidney. Aciclovir crystalline nephropathy is more common when aciclovir is given as a rapid infusion and in patients with dehydration and preexisting renal impairment. Adequate hydration, a slower rate of infusion, and dosing based on renal function may reduce this risk.The aciclovir metabolite 9-Carboxymethoxymethylguanine (9-CMMG) has been shown to play a role in neurological adverse events, particularly in older people and those with reduced renal function. Topical therapy
Aciclovir topical cream is commonly associated (≥1% of patients) with: dry or flaking skin or transient stinging/burning sensations. Infrequent adverse effects include erythema or itch.
U.S. National Library of Medicine.