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Aciclovir

DESCRIPTION
Pharmaniaga Aciclovir tablet 200 mg

Shield-shaped yellow tablet.

Pharmaniaga Aciclovir tablet 400 mg

Shield-shaped pink tablet.

COMPOSITION
Each tablet contains Aciclovir 200 mg or 400 mg.

ACTIONS
Aciclovir is converted to aciclovir monophosphate, a nucleotide, by the viral thymidine kinase of herpes simplex virus (HSV) and varicella-zoster virus (VZV). Aciclovir monophosphate is converted to the diphosphate by cellular guanylate kinase and to the triphosphate by a number of cellular enzymes. Aciclovir triphosphate interferes with HSV and VZV DNA polymerase and inhibits viral DNA replication. The triphosphate can be incorporated into growing chains of DNA by viral DNA polymerase, resulting in termination of the DNA chain.

Absorption: Bioavailability 20 % (range, 15 to 30 %). Poorly absorbed from the gastrointestinal tract. Not significantly affected by food.
 

Distribution: Widely distributed to tissues and body fluids, including brain, kidneys, lungs, liver, aqueous humor, tears, intestines, muscle, spleen, breast milk, uterus, vaginal mucosa, vaginal secretions, semen, amniotic fluid, cerebrospinal fluid (CSF) and herpetic vesicular fluid. Highest concentrations are found in kidneys, liver, and intestines. CSF concentrations are approximately 50% of plasma concentrations. Crosses the placenta, also.

Adults: Approximately 48 litres (L) per square meter of body surface (m²) (range, 37 to 57 L per m²).

Children and adolescents (1 to 18 years old): Approximately 45 L per m².

Neonates (0 to 3 month old): Approximately 28 L per m² (range, 24 to 30 L per m²).

End stage renal disease: Approximately 41 L per m².

Protein binding: Low (9 to 33%).

Biotransformation: Hepatic, only major metabolites found in urine is 9-carboxymethoxymethylguanine, which accounts for approximately 9 to 14% of the dose. This metabolite has no known antiviral activity.

Half-life: Oral - 3.3 hours.

Time to peak serum concentration: Oral - 1.7 hours.

Renal impairment (adults)

Elimination
Renal : Excreted by both glomerular filtration and tubular secretion.
Oral : Approximately 14% of total dose excreted unchanged in urine.
Faecal : Insignificant amounts (< 2%).

Lungs : Trace amounts in exhaled CO².
Dialysis : Haemodialysis : A single 6-hour period of haemodialysis reduces plasma aciclovir concentration by approximately 60%.
Peritoneal dialysis: Peritoneal dialysis does not substantially alter aciclovir clearance.

INDICATIONS
Treatment and prophylaxis of herpes genitalis, treatment of herpes zoster, herpes simplex and varicella (chicken-pox).

CONTRAINDICATIONS
Aciclovir is contraindicated in patients who have developed hypersensitivity or intolerance to the drug.

ADVERSE REACTIONS
General : fever, headache, pain, peripheral oedema, and rarely anaphylaxis.
Nervous : confusion, dizziness, hallucinations, paraesthesia, somnolence (These symptoms may be marked, particularly in older adults). Digestive : diarrhoea, elevated liver function test, gastrointestinal distress, nausea.

Haemic and Lymphatic : leucopenia, lymphadenophathy.
Musculoskeletal : myalgia.
Skin : alopecia, pruritus, rash, urticaria.

Special Senses : visual abnormalities.

Urogenital : elevated creatinine.

PRECAUTIONS
Acute renal insufficiency may occur due to precipitation of aciclovir in the renal tubules. It is most likely to occur if aciclovir is given by rapid intravenous injection, concurrently with known nephrotoxic medications, to patients who are inadequately hydrated, or to patients with renal function impairment without appropriate dosage reduction. However, acute renal failure has also been reported in patients receiving oral aciclovir.

Neuropsychiatric toxicity has been associated with high plasma aciclovir concentrations, which may occur when high doses are used, or when patients with renal function impairment are not given an appropriately lowered dose. Neuropsychiatric toxicity may also be more likely to occur in immunocompromised patients and geriatric patients.

Pregnancy / Reproduction
Fertility - Impairment of spermatogenesis, sperm motility, or morphology has not been documented in humans. However, high doses of parenteral aciclovir have caused testicular atrophy in rats and dogs. Some evidence of sperm production recovery was evident 30 days post-dose. Studies in mice given oral doses up to 450 mg/kg per day have shown that aciclovir does not impair fertility or reproduction. Studies in female rabbits given aciclovir subcutaneously subsequent to mating have shown a significant decrease in implantation efficiency, but no decrease in litter size at doses of 50 mg/kg per day.

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