Background and importance Calciphylaxis is a disease characterised by fat necrosis due to hypoperfusion from calcium accumulation in the arterioles of the skin.

In the treatment of calciphylaxis, intravenous sodium thiosulphate is usually used due to its chelating of calcium ions, a vasodilator, and antioxidant. Topical use can be an effective and well-tolerated alternative, and it also allows early treatment. This active ingredient is not marketed in any of their presentations. In these cases, a concentration of 25% thiosulphate (12.5 g in 50 mL) was recommended.

Aim and objectives To develop and validate a magistral formula of topical sodium thiosulfate and establish quality controls.

Material and methods A bibliographic search was conducted to find possible topical master formulations of sodium thiosulfate.

The galenic development and validation of the formula were achieved following the procedure for elaborating gels described in the National Formulary (PN/L/FF/003/00) and through quality control.

The quality control of the formula was carried out as established in the National Formulary: control of organoleptic characteristics (smell, colour), physical, chemical (pH controls (PN/L/CP/001/00)), and a microbiological control as Procedure 5.1.4 of the Royal Spanish Pharmacopoeia. For this purpose, five samples were taken and analysed at the beginning and after 1 month.

The risk matrix for non-sterile formulae based on the ‘Guide to Good Practice in the Preparation of Medicines in Hospital Pharmacy Services’ was applied to establish the validity period.

The samples were prepared in the non-sterile preparation area in the cleanroom. They were prepared following the Standard Operating Procedure (SOP).

Results A shelf-life of 30 days was established based on the risk matrix for non-sterile preparations with medium risk.

The organoleptic (smell, colour), physical (phase separation), chemical (pH) and microbiological characteristics remained stable during the study month. At the beginning the pH values obtained were 6.45±0.09 and after 1 month were 7.34±0.1.

Conclusion and relevance The formula remained physical, chemical and microbiological stable for 30 days and met the requirements from the galenic point of view for topical application, serving as an alternative to intravenous administration of the active ingredient.

Conflict of interest No conflict of interest