Background and importance Norwegian scabies is a severe type of scabies affecting immunocompromised patients caused by Sarcoptes scabiei var. hominis, a highly contagious variant unresponsive to the first-line scabies drugs, permethrin and ivermectine.
Aim and objectives The aim of this study was to formulate a 25% benzyl benzoate lotion for the treatment of Norwegian scabies in an oncology patient who had previously received first-line treatments without result, and to evaluate its efficacy and tolerability.
Material and methods A search of the available literature on the use of benzyl benzoate in Norwegian scabies and its physicochemical characteristics was performed. A Standard Operating Procedure was created following the guidelines of the Good Manufacturing Practice Guide.
The patient’s evolution in terms of the lesions was monitored.
Results We found literature supporting the efficacy of benzyl benzoate in Norwegian scabies. However, there is no commercially available lotion containing this active ingredient at the required concentration.
Benzyl benzoate is a lipophilic liquid, insoluble in water and miscible in fatty oils, which makes it necessary to formulate it in oily vehicles; in our case we used the ones we had available in the laboratory to make other formulations.
The formula designed was: benzyl benzoate 25 g, coconut oil 37.5 g and liquid petroleum jelly 37.5 g.
Modus operandi: weigh the components separately in a beaker. Mix the coconut oil, previously tempered in a water bath at 25°C, with the liquid petroleum jelly. Gradually add the above mixture to the benzyl benzoate and homogenise. Package in a polypropylene bottle.
A shelf life of 30 days at room temperature was assigned according to the ‘Spanish Guide to Good Practice in the Preparation of Medicines in Hospital Pharmacy Services’.
It was administered alternately with permethrin and after 2 weeks of treatment the patient’s lesions improved and the itching disappeared.
Conclusion and relevance The preparation was effective, safe and well tolerated. However, a comparison between patients treated with this formulation and a control group with the oily vehicles alone would be necessary to ascertain whether the efficacy is due to the benzoate or to the occlusive effect of the oils on the S. scabiei. Similarly, patients treated with permethrin monotherapy should be compared with those treated with permethrin alternating with benzoate.
Conflict of interest No conflict of interest