Trikase is the brand name for Aciclovir, a synthetic purine nucleoside analogue, having activity against herpes viruses.

      
Composition

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Aciclovir is an effective and highly selective antiviral agent against herpes simplex virus types 1(HSV1), 2(HSV2), and varicella-zoster virus(VZV).

Aciclovir significantly reduces the duration of acute infection and duration of lesion healing of genital herpes; duration of pain and new lesion formation also decreases. In immunocompetent patients with localized cutaneous zoster infection Aciclovir given 800 mg 5 times daily for 7 to 10 days shortens the time to lesion scabbing , healing, reduction of the duration of viral shedding and duration of new lesion formation.

The highly selective inhibitory activity is due ti its affinity for the enzyme thymidine kinase encoded by HSV and VZV. This viral enzyme converts Aciclovir into Aciclovir monophosphate which is acted upon by cellular guanylate kinase and is converted into diphosphate, and finally into triphosphate by a number of cellular enzymes. Aciclovir triphosphate , in vitro , stops replication of herpes viral DNA in three ways :- (a) competitive inhibition of viral DNA polymerase , (b) incorpation into and termination of the growing viral DNA chain, and (c) inactivation of the viral DNA polymerase. Using plaque- reduction assays, the IC50 against herpes simplex virus isolates ranges from 0.02 to 13.5mcg/ml for HSV1 and from 0.01 to 9.9mcg/ml for HSV2; against most laboratory strains and clinical isolates of VZV, IC50 ranges from 0.12 to 10.8mcg/ml.

Aciclovir has protein binding ranging from 9% to 33%, plasma elimination half life ranging from 2.5 to 3.3 hours and has average oral bioavailability of 10% to 20%.

For the treatment of herpes simplex,Recurrent herpes,Labialis, genital herpes, herpes zoster infection and chicken pox, Ophthalmic zoster.

Precautions & Contradictions

Dosage adjustment is necessary for administration of Trikase to patients with renal impairment or to patients taking potentially nephrotoxic agents. Pregnant / lactating mothers wishing to receive therapy with Trikase should consult with their physician.

Adverse Reactions

Thec most frequent adverse events reported include nauses and / or vomiting, diarrhoea, myalgia, alopecia, erythema multiforme, urticaria, etc.

 Drug Interactions

With cyclosporine - increase in serum creatinine level along with high aciclovir level accompanied by reversible acute tubular necrosis may occur.

With zidovudine- severe drowsiness and lethargy may develop.

With probenecid - bioavailability and terminal plasma half life of Aciclovir is increated with decreased renal clearance.

Dosage And administration

1. HERPES SIMPLEX

a. Therapeutic : (i) For adults and children > 2 years :-- Tablets - 200 mg 5 times daily (4 hourly) for 5 to 10 days. Cream - Apply 5 times a day every 4 hourly interval (approx) for 5 to 6 days. Further for 5 -6 days, if needed.

(ii) For immunocompromised patients : -- Tablets- 400 mg 4 to 5 times daily for 5 to 10 days. Cream - Apply 5 times a day every 4 hourly a interval (approx) for 5 to 6 days.; further for 5 to 6 days , if needed.

b. Prophylactic : For adults (immunpcompromised) : Tablets 200 - 400 mg 5 times daily during the period of risk.

2. GENITAL HERPES

A. Acute therapy for adults : Tablets 200 mg 5 times daily for 10 days. Cream - Apply 5 times a day every 4 hourly interval (approx) for 5 to 6 days if needed.

B. Chronic suppressive for recurrent disease : Tablets 400 mg 2 times daily or 200 mg 5 times daily for 1 year. ( Review every 6 months / 12 months).

C. Intermittent therapy for frequent recurrent episodes : Tablets 200 mg 5 times daily for 5 days -- therapy initiated at the earliest feature of recurrence. Cream - Apply 5 times a day every 4 hourly interval (approx) for 5 to 6 days ; further for 5 to 6 days , if needed.

D. Prophylactic( immunocompromised) : Tablets 200 - 400 mg 5 times daily during the period of risk.

3. CHICKEN POX & HERPES ZOSTER

Acute therapy -----

a. Adults : Tablets 800 mg 5 times daily for 7 days.

b. Children ( between 2 to 12 years ) : Tablets 20mg/kg body weight 4 times daily for 5 days. Cream : Apply 5 times a day every 4 hourly interval (approx) for 5 to 6 days, if needed.

Packing

Tablets : Strips of 10 tablets.

Cream : Collapsible tubes 5 mg.