Pharmacology
Mechanism of Action
Acyclovir is converted to acyclovir monophosphate by virus-specific thymidine kinase then further converted to acyclovir triphosphate by other cellular enzymes. Acyclovir triphosphate inhibits DNA synthesis and viral replication by competing with deoxyguanosine triphosphate for viral DNA polymerase and being incorporated into viral DNA.
Pharmacokinetics/Pharmacodynamics
Absorption
Not detected in blood by existing bioanalytical methods
Excretion
Trace quantities are detectable in the urine but are not therapeutically relevant
Use: Labeled Indications
Herpetic keratitis: Treatment of acute herpetic keratitis (dendritic ulcers) in patients with herpes simplex (HSV-1 and HSV-2) virus
Contraindications
Hypersensitivity to acyclovir, valacyclovir, or any component of the formulation
Dosage and Administration
Dosing: Adult
Herpetic keratitis: Ophthalmic: Apply a ½-inch ribbon of ointment in the lower cul-de-sac of the affected eye(s) 5 times daily (approximately every 3 hours while awake) until the corneal ulcer heals, then apply a ½-inch ribbon 3 times daily for 7 days.
Dosing: Geriatric
Refer to adult dosing.
Dosing: Pediatric
Herpes simplex keratitis: Children ≥2 years and Adolescents: Ophthalmic: Apply a 1 cm ribbon in the lower eyelid of affected eye(s) 5 times a day (~every 3 hours while awake) until corneal ulcer heals, then apply a 1 cm ribbon 3 times daily for 7 more days
Administration
Ophthalmic: For topical ophthalmic use only; avoid touching tip of applicator to eye(s) or other surfaces. After application close the eye(s) for 1 to 2 minutes; excess ointment may be wiped away.
Storage
Store at 20°C to 25°C (68°F to 77°F).
Drug Interactions
There are no known significant interactions.
Adverse Reactions
1% to 10%: Ophthalmic: Eye pain, follicular conjunctivitis, punctate keratitis, stinging of eyes
<1%, postmarketing, and/or case reports: Angioedema, blepharitis, type I hypersensitivity reaction, urticaria
Warnings/Precautions
There are no warnings listed in the manufacturer’s labeling.
Pregnancy
Pregnancy Considerations
Acyclovir has not been detected in the blood following ophthalmic administration; limited systemic absorption would limit potential exposure to the fetus. Results from a pregnancy registry, established in 1984 and closed in 1999, did not find an increase in the number of birth defects with exposure to systemic acyclovir when compared to those expected in the general population.
Patient Education
- Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
- Patient may experience stinging. Have patient report immediately to prescriber vision changes, eye pain, or severe eye irritation (HCAHPS).
- Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.
