Background and Importance Monkeypox (MPX) is a zoonosis caused by an orthopoxvirus transmitted by droplets, direct contact or fomites. Different signs and symptoms are caused, including a variety of skin lesions.

Aim and Objectives The aim is to evaluate the response of vesiculo-pustular lesions to treatment with a topical magistral formulation (MF) of cidofovir.

Material and Methods On a second-level hospital, during September-November 2022, a MF of topical 1% cidofovir in Base Beeler was developed by the pharmacotechnical area for the treatment of papillomatous lesions in the facial region, perianal area and extremities associated to the MPX diagnosis.

The patient‘s evolution was monitored for 4 months, variables were collected, based on the electronic medical records and the centre’s prescription records.

Results A 31-year-old male was admitted in July 2022 after 7–10 days of uncontrolled pain in the perianal area and skin lesions on the face and torso of 3–4 days of evolution. Suspicion of MPX led to a request for Orthopoxvirus real-time PCR. Diagnosis was confirmed with complete serology and positive detection for HIV (stage C3) and coronavirus.

Initially, the lesions were treated with 1/1000 zinc sulfate and topical fusidic acid every 12 hours. Given the poor response, fusidic acid was modified for topical Liade® (antibiotic ointment: polymyxin B sulfate, neomycin and bacitracin). It was also added Apodrex®, sterile dressing applied to the perianal lesion for the absorption of exudate.

Due to lack of response the Pharmacy service was requested to develop a topical 1% Cidofovir MF; Zinc sulfate was discontinued and Liade® was maintained.

The regimen was one application to each lesion twice a day, as well as Liade®.

Vesiculo-pustular lesions in necrotic phase evolved to crusty phase and then to lesions with granulation tissue and some of them even to healing process.

Four months later, due to lack of response and without achieving the complete disappearance of the lesions, it was returned to the initial treatment.

Conclusion and Relevance In the absence of consensus on the treatment of lesions caused by MPX, the application of topical 1% cidofovir improves these lesions partially, some of them up to the scarring phase. It can be considered as an alternative to zinc sulfate treatment.

Conflict of Interest No conflict of interest.