1. Introduction
According to the last European guidelines (Citation1) and Cochrane review (Citation2), 5% permethrin cream and oral ivermectin are considered the most effective therapies of scabies. However, some recent European studies suggest the appearance of resistance of Sarcoptes scabies var. hominis to permethrin (Citation3–7). This occurrence is possible; however, in our personal clinical experience, some cases of permethrin resistance are actually cases of pseudoresistance (Citation8). We present the results of a sponsor-free study about the use of a foam containing 0.165% pyrethrins and 1.65% piperonyl butoxide in a group of patients with scabies who were resistant to permethrin.
2. Patients and methods
In 348 patients the clinical diagnosis of scabies was confirmed by means of microscopical examination: it was considered positive when adults or eggs or feces of Sarcoptes scabies var. hominis were visible. All patients were treated with 1 application/day for 2 consecutive days of 5% permethrin cream. The latter was stored in refrigerator and applied as cool cream on the entire skin surface, including nails. The cream was left on the skin for 12 h. Approximately 90 g/day of cream were applied. No other topical and/or systemic drugs were allowed, except for a cleanser with 0.4% chlorhexidine digluconate (2 cleanings/day). The treatment with permethrin was repeated in all patients 7–10 days later (Citation9).
3. Results
Thirty-four patients (9.7%) [23 Caucasians and 11 non-Caucasians (25 males and 9 females, with an age ranging from 18 to 68 years)] were clinically and microscopically resistant to permethrin. They were therefore treated with a thermolabile foam containing 0.165% pyrethrins and 1.65% piperonyl butoxide (1 application/day for 2 consecutive days). The treatment was repeated in all patients 7–10 days later. Clinical and microscopical recovery was observed in 27 out of 34 patients (79.4%). Five patients (14.7%) reported a burning sensation, in particular on the glans: in one patient it was necessary to stop the treatment.
4. Discussion
Literature data about the use of the combination of pyrethrins and piperonyl butoxide in scabies are limited (Citation10–12). In a prospective, randomized, investigator-blinded trial, the foam containing pyrethrins-piperonyl butoxide was compared with 5% permethrin cream in 40 patients. The foam was at least as effective as permethrin. In comparison with permethrin, the foam induced a more rapid and complete resolution of itching (Citation10). In another study, 20 patients (12 males and 8 females, aged 1-65 years) with a diagnosis of scabies confirmed by videodermatoscopy were enrolled. The foam with permethrin and piperonyl butoxide was applied to the entire skin surface once a day for 2 consecutive days. To detect treatment response, videodermatoscopy evaluation of 2 targeted skin sites for each patient was performed at baseline and at 12, 24, 36 and 48 h. In all patients, videodermatoscopy showed active mite migration within burrows at 12 h. At 24 h, there was no evidence of active mite migration, and the majority of patients reported a significant improvement of itching. At 48 h, an amorphous material, probably resulting from mite decomposition, was detected at one end of an empty burrow in the majority of patients. Skin scrapings at 48 h showed only mite remnants in all patients. None of the 20 patients showed signs of infestation by videodermatoscopy at targeted skin sites at a 2-week post-baseline visit (Citation11). In a multicenter, randomized, comparative, parallel group, investigator-blinded trial, the efficacy and tolerability of the association pyrethrins/piperonyl butoxide foam was compared with 25% benzyl benzoate lotion. A total of 240 convicted patients, enrolled in eight Italian jails, were treated with the foam for 3 consecutive days (120 patients) or the lotion for 5 consecutive days (120 patients). At week 2, a total of 75% and 71% of patients showed a complete clinical cure rate in the foam and lotion groups, respectively. At week 4, the percentage of totally cured patients increased to 95% and 91% in the foam and lotion groups, respectively. At week 4, 5% in the foam group and 9% in the lotion group complained of itching. Burning sensation and irritant contact dermatitis were more common in the lotion group: a total of 95% of patients in the foam group had a good tolerability score in comparison with 41% in the lotion group. The authors concluded that a 3-day treatment with pyrethrins and piperonyl butoxide is at least as effective as a 5-day treatment with benzyl benzoate in convicted patients with scabies (Citation12). According to the results of our study, based on a rather small, although selected group of patients who were resistant to permethrin, the combination of 0.165% pyrethrins/1.65% piperonyl butoxide foam can be taken into consideration in the treatment of patients with permethrin-resistant scabies: as previously mentioned, we got a complete clinical and microscopical remission in 27 out of 34 patients (79.4%). The foam must be used correctly because it can be irritant. Storing the foam in the refrigerator and applying it cold, as for permethrin cream, can limit the irritation (Citation9).
Disclosure statement
The authors do not have any conflict of interest. This research did not receive any specific grant.
Additional information
Funding
References
- Salavastru CM, Chosidow O, Boffa MJ, et al. European guideline for the management of scabies. J Eur Acad Dermatol Venereol. 2017;31(8):1–2. doi: 10.1111/jdv.14351.
- Rosumeck S, Nast A, Dressler C. Evaluation of ivermectin vs permethrin for treating scabies-summary of a cochrane review. JAMA Dermatol. 2019;155(6):730–732. doi: 10.1001/jamadermatol.2019.0279.
- Sunderkötter C, Aebischer A, Neufeld M, et al. Increase of scabies in Germany and development of resistant mites? Evidence and consequences. J Dtsch Dermatol Ges. 2019;17(1):15–23. doi: 10.1111/ddg.13706.
- Mang R, Kremer A, Lehmann P, et al. Skabies – klinische Therapieresistenz auf Permethrin: Fallbeschreibungen und eine kritische Auseinandersetzung mit den aktuellen Therapieempfehlungen. Hautarzt. 2021;72(7):595–599. doi: 10.1007/s00105-021-04783-8.
- Meyersburg D, Kaiser A, Bauer JW. Loss of efficacy of topical 5% permethrin for treating scabies: an Austrian single-center study. J Dermatolog Treat. 2022;33(2):774–777. doi: 10.1080/09546634.2020.1774489.
- Yürekli A. Is there a really resistance to scabies treatment with permethrin? In vitro killing activity of permethrin on sarcoptes scabiei from patients with resistant scabies. Dermatol Ther. 2022;35:e15260.
- Mayer KE, Biedermann T, Posch C. European scabies challenge: what about permethrin-resistant mites? J Eur Acad Dermatol Venereol. 2022;36(9):e712–e713. doi: 10.1111/jdv.18181.
- Veraldi S, Schianchi R, Silvio M, et al. Pseudoresistance to permethrin in scabies. J Infect Dev Ctries. 2023;17(5):713–715. (in press). doi: 10.3855/jidc.17750.
- Veraldi S, De Micheli P, Schianchi R, et al. A new treatment regimen with per- methrin in scabies. G Ital Dermatol Venereol. 2018;153:491–493.
- Amerio P, Capizzi R, Milani M. Efficacy and tolerability of natural synergised pyrethrins in a new thermo labile foam formulation in topical treatment of scabies: a prospective, randomised, investigator-blinded, comparative trial vs. Permethrin Cream. Eur J Dermatol. 2003;13:69–71.
- Micali G, Lacarrubba F, Tedeschi A. Videodermatoscopy enhances the ability to monitor efficacy of scabies treatment and allows optimal timing of drug application. J Eur Acad Dermatol Venereol. 2004;18(2):153–154. doi: 10.1111/j.1468-3083.2004.00858.x.
- Biele M, Campori G, Colombo R, et al. Efficacy and tolerability of a new syner- gized pyrethrins thermofobic foam in comparison with benzyl benzoate in the treatment of scabies in convicts: the ISAC study (Studio Della Scabbia in Ambiente Carcerario). J Eur Acad Dermatol Venereol. 2006;20(6):717–720. doi: 10.1111/j.1468-3083.2006.01623.x.