Acyclovir (Topical)
Indications
Acyclovir cream is a herpes simplex virus
(HSV) nucleoside analogue DNA polymerase inhibitor indicated for the
treatment of recurrent herpes labialis (cold sores) in immunocompetent
adults and adolescents 12 years of age and older.
Pharmacology
Acyclovir is an antiviral drug active
against herpes simplex virus. Acyclovir is a synthetic purine nucleoside
analogue with cell culture and in vivo inhibitory activity against HSV
types 1 (HSV-1) and 2 (HSV-2). The inhibitory activity of acyclovir is
highly selective due to its affinity for the enzyme thymidine kinase
(TK) encoded by HSV. This viral enzyme converts acyclovir into acyclovir
monophosphate, a nucleotide analogue. The monophosphate is further
converted into diphosphate by cellular guanylate kinase and into
triphosphate by a number of cellular enzymes. In cell culture, acyclovir
triphosphate stops replication of herpes viral DNA. This inhibition is
accomplished in 3 ways: 1) competitive inhibition of viral DNA
polymerase, 2) incorporation into and termination of the growing viral
DNA chain, and 3) inactivation of the viral DNA polymerase.
Dosage & Administration
Acyclovir cream should be applied five
times per day for four days. Therapy should be initiated as early as
possible following the onset of signs or symptoms of herpes labialis
i.e., during the prodrome or when lesions appear. For adolescents 12
years of age and older, the dosage is the same as in adults.
Interaction
Clinical experience has identified no
interactions resulting from topical or systemic administration of other
drugs concomitantly with Acyclovir cream. Due to minimal systemic
absorption of Acyclovir cream, systemic drug interactions are unlikely.
Contraindications
Acyclovir cream is contraindicated in
patients with known hypersensitivity to acyclovir, valacyclovir, or any
component of the formulation.
Side Effects
The most common adverse reactions at the
site of topical application were dry lips, desquamation, dryness of
skin, cracked lips, burning skin, pruritus, flakiness of skin, and
stinging on skin; each adverse reaction occurred in less than 1% of
patients receiving Acyclovir cream and placebo. Three patients on
Acyclovir cream and one patient on placebo discontinued treatment due to
an adverse event.
Pregnancy & Lactation
Pregnancy Category B. There are no adequate
and well-controlled studies of acyclovir cream in pregnant women.
Acyclovir cream should be used during pregnancy only if the potential
benefit justifies the potential risk to the fetus. It is not known
whether topically applied acyclovir is excreted in breast milk. Systemic
exposure following topical administration is minimal.
Precautions & Warnings
Acyclovir cream should only be applied on
the affected external aspects of the lips and face in patients with
herpes labialis. Because no data are available, application to human
mucous membranes is not recommended. Acyclovir cream is intended for
cutaneous use only and should not be used in the eye or inside the mouth
or nose. Cream has a potential for irritation and contact. The effect
of Acyclovir cream has not been established in immunocompromised
patients.
Use in Special Populations
Pediatric Use: An
open-label, uncontrolled trial with Acyclovir cream 5% was conducted in
113 patients aged 12 to 17 years with recurrent herpes labialis. In this
trial, therapy was applied using the same dosing regimen as in adults
and subjects were followed for adverse events. The safety profile was
similar to that observed in adults. Safety and effectiveness in
pediatric patients less than 12 years of age have not been established.
Geriatric Use: Clinical studies of acyclovir cream did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. Systemic absorption of acyclovir after topical administration is minimal.
Geriatric Use: Clinical studies of acyclovir cream did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. Systemic absorption of acyclovir after topical administration is minimal.
Therapeutic Class
Topical Antiviral preparations
Storage Conditions
Store Acyclovir cream at room temperature between 20°C to 25°C
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