Clinical Trial
In the development of Skabi-Rid, the following clinical trial was performed: a single centre randomised investigator blind, parallel group study to determine the safety and efficacy of a single application of permethrin 5% lotion versus two applications of a benzyl benzoate 25% emulsion in the treatment of scabies. The study was performed by SACT (South African Clinical Trials) and led by Prof. Otto Müller.
Primary Objective
To evaluate the efficacy of a single application of permethrin 5% lotion as compared to a benzyl benzoate 25% emulsion applied as two separate applications 12 hours apart in the treatment of scabies as determined by the treatment response at day 29 or early discontinuation visit.
Secondary objectives
- To evaluate the safety and tolerability of a single application of permethrin 5% lotion as compared to two separate applications of a benzyl benzoate 25% emulsion, 12 hours apart, as determined by reported and observed adverse events and changes in clinical laboratory values.
- To evaluate the efficacy of a single application of permethrin 5% lotion as compared to two separate applications of benzyl benzoate 25% emulsion at day 15.
- To evaluate the difference between the two treatment groups in the changes in the severity of pruritis from baseline to Day 29 on the modified pruritis score scale.
- To evaluate the differences between the two treatment groups in the changes in severity of infestation from baseline to Day 29 on a 5-point scale.
Methodology
Single centre investigator-blind, randomised, parallel group, active-controlled study in patients with scabies.
Number of patients
A total of 120 volunteers (36.7% male and 63.3% female) were randomised — 60 volunteers to permethrin 5% lotion and 60 volunteers to benzyl benzoate 25% emulsion. All volunteers randomised received the relevant investigational products.
Diagnosis and main criteria for inclusion
Volunteers with clinical and/or parasitological signs and symptoms compatible with scabies defined as:
- demonstration by light microscopy of eggs, larvae, mites or faecal pellets in skin scrapings, or
- presence of at least three of the following clinical criteria: demonstration of a burrow; presence of scabetic lesions at the classical sites; nocturnal pruritis; family history of similar illness.
To prevent re-infection by untreated individuals, all infected household members were invited to participate in the study. Those who did not participate had to agree to be treated with benzyl benzoate 25% emulsion for the primary candidate to be eligible.
Products
Test product: Permethrin 5% lotion — TomarMed (Pty) Ltd. Topical application. Batch number TT031.
Reference product: Benzyl benzoate 25% emulsion (Ascabiol) — Pharmacare Ltd. Topical application. Batch No: 226686. Permethrin 5% matching placebo lotion — TomarMed (Pty) Ltd, batch number TT030.
Treatment and duration
Volunteers were randomised in a 1:1 ratio, investigator-blind design to one of the following treatments:
- Treatment A: benzyl benzoate 25% emulsion (two applications 12 ± 2 hours apart)
- Treatment B: permethrin 5% lotion (single application of active followed by a single application of placebo 12 ± 2 hours later)
Willing household contacts were treated with benzyl benzoate 25% emulsion according to the South African Department of Health Standard Treatment Guidelines (1998) for Primary Health Care.
Primary efficacy endpoint
Treatment response on Day 29 or early discontinuation visit, defined as:
- Cure: No pruritis, no skin lesions, absence of mites or their products on microscopy.
- Moderate improvement: Improvement in pruritis, > 50% reduction in skin lesions, no new lesions, absence of mites or their products on microscopy.
- Mild improvement: Improvement in pruritis, ≤ 50% reduction in skin lesions, no new lesions, absence of mites or their products on microscopy.
- Treatment failure: No improvement in pruritis and no reduction in the number of skin lesions, or appearance of skin lesions, or presence of mites or their products on microscopy.
Summary of Results
Efficacy: Treatment with a single application of permethrin 5% lotion was associated with a 70.7% cure rate on Day 29, compared to a 67.8% cure rate in volunteers treated with two applications of benzyl benzoate 25% emulsion (p ≥ 0.5). A greater proportion of volunteers in the permethrin treated group had no residual skin lesions at Day 29 (86.2%), compared to those treated with benzyl benzoate (76.3%).
Safety: Permethrin lotion 5% and benzyl benzoate 25% emulsion were both well tolerated. Most adverse events were mild in intensity and were considered unrelated to the investigational products. The most common adverse event that appeared to be drug related was a transient burning sensation of the skin starting soon after the first application of scabicide. This is a known side effect of benzyl benzoate and to a lesser extent, permethrin. No significant changes were seen in any of the laboratory parameters during the study.
Conclusion
Permethrin 5% lotion and benzyl benzoate 25% emulsion demonstrated similar efficacy with regard to the parameters measured. Permethrin 5% lotion offers an advantage for compliance of treatment over benzyl benzoate because of its superior safety profile and the fact that it involves just a single application.
The study outcome justified the recommendation of the South African Standard Treatment Guidelines and Essential Drugs List for Primary Health Care, that permethrin 5% formulation be used as first line treatment for scabies.