SITAVIG
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SITAVIG (SITAVIG).
Sitavig (acyclovir) is a synthetic nucleoside analogue that inhibits viral DNA replication. It is phosphorylated to acyclovir triphosphate, which competitively inhibits viral DNA polymerase and incorporation into viral DNA, leading to chain termination.
| Metabolism | Acyclovir is metabolized to a small extent by aldehyde oxidase and alcohol dehydrogenase. The major metabolite is 9-carboxymethoxymethylguanine (CMMG). It is primarily excreted renally via glomerular filtration and tubular secretion. |
| Excretion | Primarily renal; approximately 80% of the dose is excreted unchanged in urine within 24 hours. Minor fecal excretion (less than 10%). |
| Half-life | Terminal elimination half-life is approximately 20 hours in adults with normal renal function. In patients with renal impairment (CrCl <30 mL/min), half-life increases to up to 40 hours, necessitating dose adjustment. |
| Protein binding | Approximately 15% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is about 0.7 ± 0.2 L/kg, indicating distribution into total body water and some tissue binding. |
| Bioavailability | Bioavailability of the buccal tablet is approximately 70% relative to oral acyclovir, with sustained absorption across the buccal mucosa. |
| Onset of Action | Mucoadhesive buccal tablet: Clinical antiviral effect (reduction of viral shedding and lesion healing) begins within 30 minutes to 1 hour after application, with maximum plasma concentrations achieved at 1.5 to 2 hours. |
| Duration of Action | Duration of antiviral effect is approximately 12 hours, supporting twice-daily dosing. Lesion healing and symptom resolution typically occur within 4 to 6 days; therapy should be continued for 7 days. |
Topical: Apply one 50 mg buccal tablet to the upper gum above the incisor region once daily for 14 days.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Safety and effectiveness in pediatric patients below 16 years have not been established. |
| Geriatric use | No specific dose adjustment recommended; monitor for adverse effects due to potential age-related decline in organ function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SITAVIG (SITAVIG).
| Breastfeeding | Unknown if distributed in human milk. Due to potential adverse effects in nursing infants (e.g., growth suppression from ribavirin), discontinue breastfeeding or discontinue drug. M/P ratio not available. |
| Teratogenic Risk | Pregnancy Category X: Contraindicated due to risk of fatal fetal toxicity from ribavirin component (teratogenic in all animal species) and peginterferon alfa-2a (associated with increased fetal loss in primates). Avoid pregnancy during therapy and for 6 months after completion in female patients and female partners of male patients. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to acyclovir, valacyclovir, or any component of the formulation"]
| Precautions | ["Renal impairment: Use with caution in patients with renal impairment; dose adjustment recommended.","Dehydration: Ensure adequate hydration to prevent crystalluria.","Neurologic effects: Use with caution in patients with neurological conditions; may cause agitation, seizures, or encephalopathy.","Immunocompromised patients: Safety and efficacy not established for HIV patients with CD4 count < 100 cells/mm³."] |
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| Fetal Monitoring |
| Negative pregnancy test required immediately before initiation, monthly during therapy, and 6 months post-therapy. Monitor for fetal exposure via ultrasound if pregnancy occurs. |
| Fertility Effects | Reversible oligospermia reported with ribavirin; may impair male fertility during treatment. No specific data on female fertility. Contraceptive counseling mandatory for both sexes during and 6 months after treatment. |