FDA approves acyclovir buccal tablets for recurrent herpes labialis

In April 2013, the Food and Drug Administration approved acyclovir (Sitavig, BioAlliance Pharma) mucoadhesive buccal tablets (MBT) for the treatment of recurrent herpes labialis in immunocompetent adults. Acyclovir is a synthetic purine nucleoside that is converted into a triphosphate form through enzymatic reactions. Acyclovir triphosphate inhibits replication of herpes viral DNA through insertion into the viral DNA chain and subsequent termination. Each tablet contains 50 mg of acyclovir. Acyclovir MBT is contraindicated in patients with hypersensitivity to acyclovir, milk protein concentrate, or any other components of the product.

Efficacy

In a randomized, double-blind, placebo-controlled trial, 378 patients were treated with acyclovir MBT and 397 were treated with placebo. A single dose of acyclovir MBT 50 mg was given to patients with recurrent herpes labialis, of which the majority (68.4%) had five or more episodes in the previous year. Patients’ average age was 41 years of age; most were Caucasian (94.9%) and female (68.6%). Patients were instructed to apply acyclovir MBT within one hour of appearance of prodromal symptoms, with the same instructions as for the approved dosing.

Duration of the herpes labialis episode for patients in the acyclovir MBT group was approximately one-half day less than that for patients taking placebo. Additional outcomes showed that patients randomized to acyclovir MBT experienced less time from prodromal symptoms to healing, more patients had abortive episodes that did not progress to vesicular lesions, and duration of abortive episodes was briefer. For patients who agreed to follow up at nine months, the time to recurrence of a herpes labialis episode was significantly delayed - by 37 days  - for those treated with acyclovir MBT, compared to recurrence time for those treated with placebo.

Safety

The same randomized trial evaluated patients for safety outcomes. Treatment of emergent adverse events occurring in 1% or more of the patients included headache (1% acyclovir MBT and 2% placebo) and application site pain (1% in both groups). No one discontinued drug therapy due to adverse events. In each group, one report of headache was classified as severe. Other adverse events reported by 1% or more of the patients included dizziness, lethargy, gingival pain, aphthous stomatitis, application site pain, application site irritation, erythema, and rash (all 1% in the acyclovir MBT group), and headache (3% in the acyclovir MBT group).

Although no studies of drug-interactions have been performed, they are not expected to be significant as there is minimal systemic absorption with acyclovir MBT. Acyclovir is primarily excreted unchanged in the urine through active tubular secretion. Therefore, drugs that compete for tubular secretion, theoretically, may increase acyclovir levels.

Dosing

Acyclovir MBT should be used within one hour of emergence of prodromal symptoms prior to the appearance of signs of herpes labialis. One MBT should be applied to the canine fossa, the area of the upper gum right above the incisor tooth, on the side of the mouth exhibiting symptoms. The MBT should be held in place with slight pressure over the upper lip for 30 seconds to ensure proper adhesion. The MBT has a flat side and a rounded side; the manufacturer suggests that the rounded side be applied facing the gum for comfort. Over the course of the day, the MBT will slowly dissolve. Should the MBT fall out of place or fail to adhere within the first 6 hours, the MBT should be repositioned immediately. If the patient swallows the MBT within the first 6 hours, she should drink a glass of water and apply a new MBT to the same area. If the MBT falls out of place or is swallowed after 6 hours, nothing further need be done. Patients should be instructed not to chew, crush, swallow, or suck on the MBT. While the MBT is in place, patients can eat and drink as usual. Actions such as chewing gum, touching or pressing the MBT after it is attached, wearing upper dentures or brushing teeth should be avoided. Patients with dry mouth should drink plenty of water. No dosing recommendations are available for patients with renal dysfunction.

Diana M. Sobierajis assistant professor of pharmacy practice, University of Connecticut School of Pharmacy, Storrs, Conn.