Background and importance Recurrent respiratory papillomatosis (RRP) is a rare disease that predominantly affects the larynx and trachea, but it can spread to any other part of the respiratory tract. The aetiological agent of RRP is human papilloma virus types 6 and 11. Treatment options in RRP include surgical excision and adjuvant antiviral drug administration.

Aim and objectives To describe the preparation of intralesional cidofovir as a magistral formula and its clinical effect in a patient with RRP.

Material and methods We performed a descriptive study of RRP in a 3-year-old child with dysphonia since birth. Papillomatous lesions were located on the vocal folds and the laryngeal surface of the epiglottis. The patient underwent a surgical intervention in September and November 2018. In January 2019, due to new recurrence, physicians decided to start treatment with 5 mg/mL intralesional cidofovir, one injection of 10 mg every 2 weeks.

Results The preparation was prepared taking 0.2 mL (15 mg) from the commercial presentation and filling it with physiological saline solution to obtain a final volume of 3 mL, resulting in a 5 mg/mL concentration. The mixture was prepared in a vertical laminar flow hood and aseptically filled into luer lock syringes, each one containing 1 mL, and the rest of the mixture was thrown out. The preparation was kept in cold storage (2–8°C). The shelf life of the prefilled syringes for intralesional administration was limited to 24 hours in order to minimise the risk of microbial contamination.

The patient received six injections of cidofovir from February to May 2019. The child presented good tolerance without reduction of lesions and symptoms, despite a slight dose increase in the last injection. After failure of intralesional cidofovir, the patient started adjuvant treatment with alpha-2b-interferon and indole-3-carbinol in order to decrease the frequency of papilloma recurrence and reduce the number of surgeries required.

Conclusion and relevance The formulation was simple, and it did not take a long time to prepare. However, in our case, intralesional cidofovir administration did not seem to be an effective treatment of RRP, although there is evidence available suggesting otherwise.

References and/or acknowledgements No conflict of interest.