Acyclovir
Drug Class
Therapeutic class: Antiviral agent
Pharmacologic class: Synthetic nucleoside (guanine) analogue.
Mechanism of Action
Acyclovir is selectively activated in virus-infected cells by viral thymidine kinase to acyclovir monophosphate, then converted to the active triphosphate form by host enzymes. Acyclovir triphosphate inhibits viral DNA polymerase and causes chain termination, preventing viral DNA synthesis.
Allied Formulations
Oral: Tablets (200 mg,400 mg,800 mg)
Capsule: 200 mg
Suspension: 200 mg/5ml
IV: 250 mg/5ml,500 mg/10ml,1g/20ml
Indications
| Labelled Indications and Dose | Off-labelled Indications and Dose | ||
|---|---|---|---|
| Indications | Dose | Indications | Dose |
| Genital Herpes | IV:5-10mg/kg/dose TDS for 2-7 days | Oral: 200mg 5 times a day For 7-10 days | Bell’s Palsy | Oral: 400mg 5 times a day For 7 days |
| Recurrent Genital Herpes | IV Dose as genital herpes f/b Oral: 400mg 3 times a day For 5 days | Varicella | IV: 10-15mg/kg every 8 hrs for 7-10 days |
| HSV Encephalitis | IV: 10mg/kg every 8 hrs For 14-21 days | CMV Infection | Adults ≥40kg-IV: 500mg/m²/dose TDS Oral: 800mg 4 times a day |
| Varicella | Oral (>40 Kg): 800mg 4 times a day for 5 days | - | - |
| Herpes Zoster | IV: 10mg/kg/dose TDS for 7 days | Oral : 800mg 5 times daily for 7-10 days | - | - |
Dose Adjustment
Dose adjustment is required in patients with renal impairment. The dose should be reduced or the dosing interval extended based on creatinine clearance. Dose adjustment is recommended when CrCl is <25 mL/min for oral therapy and <50 mL/min for IV. Adequate hydration is essential during IV therapy.
Clinical Pharmacy Considerations
- Assess baseline renal function before initiation of therapy
- Adjust dose according to creatinine clearance to prevent accumulation
- Ensure adequate hydration, particularly during IV administration
- Administer IV acyclovir as a slow infusion over at least 1 hour
- Monitor for signs of neurotoxicity (confusion, hallucinations, tremors), especially in renal impairment
- Counsel patients on adherence to therapy and adequate fluid intake
