Interim Guidelines for Smallpox Response and Management in Scotland in the Post-Eradication era

Cidofovir is a nucleoside analogue active against virtually all DNA viruses, including herpes group viruses, adenoviruses and poxviruses.
There is no data on the effectiveness of cidofovir against vaccinia or variola in humans. It is active against variola in vitro, and can prevent or attenuate vaccinia in mice and monkeypox in non-human primates. It has been used successfully to treat molluscum contagiosum and orf in humans.
Cidofovir is in short supply and should be reserved for those with definite indications and prioritised to those who will derive the most benefit:

To treat vaccine complications.
To attenuate smallpox disease in contacts who have not been adequately protected by vaccination.

Treatment of vaccine complications should be initiated at the first sign of adverse effects. Complications may be treated by cidofovir or VaIG (see Appendix 13) depending on supplies.
Cidofovir may be used to treat all complications of vaccination.
Cidofovir may be given, supplies permitting, to attenuate smallpox disease in primary contacts who are vaccinated more than 8 days after their first exposure to infection. This includes primary contacts in whom the first vaccination shows no sign of a "take" on the third day. Cidofovir should be given concurrently with (re) vaccination.
Supplies permitting, it may also be considered for the treatment of established smallpox disease.
The dose of cidofovir is 5mg/kg body weight. It should be infused in at least 100ml normal saline over at least one hour. Further doses should be repeated if necessary after an interval of not less than seven days.
Cidofovir is toxic, particularly to the kidneys. To minimise nephrotoxicity, the patient should be well hydrated, and probencid should be administered orally: 2g prior to the infusion, 1g one hour after the infusion has finished and 1g eight hours after the infusion has finished.
Other adverse effects of cidofovir include asthenia, nausea, headache, alopecia and reversible neutropaenia.

The Scottish Government