Zervira

Indications

Amenamevir is an antiviral tablet used in adults to treat shingles (herpes zoster), the painful blistering rash caused by reactivation of the chickenpox virus. It works best when started as early as possible, ideally within 5 days of the rash appearing.

How It Works

Amenamevir blocks the helicase-primase enzyme complex that the varicella-zoster virus needs to unwind and copy its genetic material. This stops the virus from multiplying, which helps the rash heal faster and reduces the period of new blister formation. Unlike some other antivirals, it does not need dose changes for kidney function.

Dosage and Administration

The usual adult dose is 400 mg (for example two 200 mg tablets) taken once a day after a meal for 7 days, or as prescribed. Take it with food, because it is absorbed poorly on an empty stomach. Complete the full course even if the rash improves.

Interactions

• Rifampicin greatly lowers Amenamevir levels and should not be used together with it.
• Other strong enzyme inducers such as Carbamazepine, Phenytoin or St John's Wort may make it less effective.
• Strong CYP3A inhibitors such as Ketoconazole, Clarithromycin or Ritonavir, and Grapefruit juice, may raise its levels.
• Amenamevir can lower the levels of some medicines broken down by CYP3A, such as Midazolam, Nifedipine or Cyclosporine; your doctor may need to adjust them.

Contraindications

• Allergy to Amenamevir or any ingredient of the tablet.
• Taking Rifampicin.

Side Effects

It is usually well tolerated. Side effects may include headache, nausea, stomach discomfort, diarrhoea, rash, and changes in liver tests or blood counts on blood tests.

Get urgent medical help if you develop swelling of the face or throat, difficulty breathing, a severe skin reaction with blisters or peeling, rash spreading to the eye with pain or vision changes, or confusion, severe headache or weakness.

Pregnancy and Lactation

Safety in pregnancy has not been established, and animal studies have shown possible effects. Use only if your doctor considers it essential. It is not known whether it passes into breast milk; avoid breastfeeding during treatment unless your doctor advises otherwise.

Precautions and Warnings

• Shingles near the eye, or in people with weak immunity, needs prompt specialist care.
• Keep blisters covered and avoid contact with pregnant women, newborns and people who have not had chickenpox until the blisters crust over.
• Not studied in children.

Overdose

There is little experience of overdose. Seek medical advice if more than the prescribed amount has been taken.

Therapeutic Class

Antiviral (helicase-primase inhibitor)

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.