Zostiva1 gm

Zostiva 1 gm is an oral antiviral prodrug of acyclovir used in immunocompetent adults and, for some indications, children, for:

• Cold sores (herpes labialis) - treatment, most effective when started at the earliest symptom (tingling, itching, or burning)
• Genital herpes - treatment of an initial episode, treatment of recurrent episodes, and chronic suppressive therapy to reduce the frequency of outbreaks; also indicated for reduction of transmission of genital herpes to a partner
• Herpes zoster (shingles) - treatment, most effective when started within 72 hours of rash onset
• Chickenpox (varicella) - treatment in children 2 years and older with a healthy immune system, started within 24 hours of rash onset

Contains Zostiva 1 gm (as Zostiva 1 gm hydrochloride) as the active ingredient, available as oral tablets, commonly in 500 mg and 1 g strengths, and as an oral suspension prepared from tablets for pediatric use.

Zostiva 1 gm is an oral antiviral medicine that is converted in the body to acyclovir, a well-established medicine for herpes-family viral infections, including cold sores, genital herpes, shingles, and chickenpox. Because Zostiva 1 gm is absorbed more efficiently than acyclovir itself, it achieves higher acyclovir blood levels with less frequent dosing, making treatment more convenient. Timing is critical for its effectiveness - it works best when started at the very first sign of an outbreak (tingling or itching for cold sores, or within specific time windows after rash onset for shingles and chickenpox) - and its dose must be adjusted in patients with reduced kidney function, given a recognized risk of kidney and neurological effects, particularly at high doses.

Therapeutic Class: Antiviral (Herpesvirus)

Zostiva 1 gm is rapidly and almost completely converted to acyclovir and the amino acid L-valine after oral administration, through first-pass intestinal and hepatic metabolism, achieving significantly higher acyclovir blood levels than an equivalent oral dose of acyclovir itself, which allows for less frequent dosing. Acyclovir is eliminated mainly by the kidneys; dose adjustment is required in renal impairment, since drug accumulation at high doses in patients with reduced kidney function is associated with an increased risk of acute kidney injury and central nervous system effects.

• Taken orally, with or without food
• Swallow tablets whole with water
• Start treatment as early as possible after symptoms begin, per the specific condition's recommended time window
• Maintain adequate hydration throughout treatment, particularly at higher doses
• For genital herpes, continue safer sex practices and avoid contact with lesions during outbreaks, since Zostiva 1 gm does not cure the infection or eliminate all risk of transmission

The following should be assessed by a healthcare professional before combining with Zostiva 1 gm:

• Other nephrotoxic medicines (such as aminoglycosides, cyclosporine, tacrolimus, or NSAIDs): may increase the risk of kidney effects when combined with Zostiva 1 gm, particularly at high doses.
• Cimetidine and probenecid: reduce the rate of conversion of Zostiva 1 gm to acyclovir and reduce acyclovir renal clearance, increasing acyclovir blood levels, though this is not generally considered clinically significant at standard doses.
• Mycophenolate mofetil (used in transplant patients): may increase blood levels of both drugs when combined with Zostiva 1 gm/acyclovir.
• Other drugs affecting bone marrow or immune function (in immunocompromised patients receiving high-dose Zostiva 1 gm): use with caution, given theoretical additive risk.

Common side effects

• Headache
• Nausea, upset stomach
• Vomiting
• Diarrhoea or constipation

Serious side effects (require prompt medical attention)

• Thrombotic thrombocytopenic purpura/haemolytic uraemic syndrome (TTP/HUS): a rare but serious blood disorder, reported particularly in patients with advanced HIV disease and in bone marrow or kidney transplant recipients receiving high doses; can be fatal - symptoms may include unusual bruising or bleeding, severe fatigue, and reduced urination.
• Acute kidney injury: more likely in elderly patients, those with underlying kidney impairment, or those receiving higher-than-recommended doses; maintain adequate hydration and use appropriate dose adjustment.
• Central nervous system effects: agitation, hallucinations, confusion, or, rarely, encephalopathy - risk is higher in elderly patients and those with reduced kidney function, particularly at high doses.
• Serious skin reactions (rare): Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis - widespread rash, blistering, or peeling skin requires immediate medical attention.
• Signs of a severe allergic reaction: difficulty breathing or swallowing, rapid heartbeat, swelling of the face or throat.

Pregnancy

Zostiva 1 gm (via its active form, acyclovir) has been used during pregnancy for genital herpes and other indications when clinically necessary, with a substantial body of clinical experience; use should be guided by the treating physician, weighing the benefit of treatment against the specific clinical situation.

Breastfeeding

Acyclovir (the active form of Zostiva 1 gm) passes into breast milk; use during breastfeeding is generally considered acceptable at standard doses, but should be discussed with a healthcare professional, particularly for high-dose or prolonged use.

• Start treatment early: effectiveness depends heavily on beginning treatment promptly - at the first symptom for cold sores, within 72 hours of rash for shingles, and within 24 hours of rash for chickenpox; delayed treatment is less effective.
• TTP/HUS risk: a rare but serious risk, mainly reported at high doses in immunocompromised patients (advanced HIV, transplant recipients); monitor for symptoms in these higher-risk groups.
• Acute kidney injury and CNS effects: use caution and ensure adequate hydration, particularly in elderly patients or those with underlying renal impairment receiving higher doses.
• Zostiva 1 gm does not cure herpes infections and does not eliminate the risk of transmission to others; continue safer sex practices for genital herpes.
• Dose reduction is required in renal impairment for all indications, particularly the higher doses used for cold sores and shingles.

Overdose, particularly in patients with renal impairment or when normal doses are given without adjusting for reduced kidney function, can cause acute kidney injury, and, in more severe cases, neurological symptoms such as confusion, agitation, or coma; a case of Zostiva 1 gm toxicity with unintentional overdose leading to neurotoxicity has been described in the medical literature. Suspected significant overdose is a medical emergency requiring prompt evaluation; treatment is generally supportive, with adequate hydration, and haemodialysis can help remove acyclovir from the blood in patients with significant renal impairment and overdose.

Store tablets at room temperature, protected from moisture, in the original container. Oral suspension prepared from tablets should be stored as directed by the pharmacy, generally refrigerated, and used within the specified in-use period (commonly up to 28 days).

• Elderly: Use caution when prescribing Zostiva 1 gm for cold sores or other high-dose regimens in this population, given increased likelihood of underlying renal impairment and increased risk of CNS adverse effects; dose adjustment based on renal function is important.
• Renal impairment: Requires dose reduction across all indications, based on creatinine clearance.
• Immunocompromised patients (such as advanced HIV or transplant recipients): Higher-dose regimens used in these populations carry an increased, though still rare, risk of TTP/HUS; use requires specialist guidance and monitoring.

Treatment duration is short and specific to each condition - 1 day for cold sores, 3-10 days for genital herpes depending on whether it is an initial or recurrent episode, 7 days for shingles, and 5 days for chickenpox in children. Suppressive therapy for recurrent genital herpes, when used, is an ongoing, ideally reviewed periodically, course determined by the treating physician.

Oral suspension for pediatric use is prepared extemporaneously from Zostiva 1 gm tablets by a pharmacist, following specific compounding instructions; the prepared suspension should be used within the specified stability period (commonly up to 28 days when refrigerated), per the manufacturer's guidance.

Drug Class: Nucleoside analogue antiviral (L-valyl ester prodrug of acyclovir)

After conversion to acyclovir, the active drug is taken up preferentially by cells infected with a herpes-family virus, where a viral enzyme converts it into its active triphosphate form. This active form is incorporated into the growing viral DNA chain in place of a normal building block, causing the chain to terminate and blocking further viral DNA synthesis. Because this process depends on a viral enzyme found mainly in infected cells, acyclovir (and therefore Zostiva 1 gm) is selectively toxic to virus-infected cells while largely sparing normal, uninfected cells.

Zostiva 1 gm is used in children 2 years and older for chickenpox (varicella), with weight-based dosing (20 mg/kg three times daily, up to a maximum of 1 g three times daily) for 5 days, started within 24 hours of rash onset. It is also used in children 12 years and older for cold sores, at the same dose as adults. Use for genital herpes in children has not been established.