In an effort to stall head lice infestations annually among the children and adult population along with the drug resistance to lindane and pyrethroids, most commonly used treatments across developed and developing markets, US FDA has issued a guidance for developing drugs for topical treatment.

Head lice infestation is widespread, affecting both children and adults. In the US, it is estimated that between 6 and 12 million infestations occur annually among children 3 to 11 years. There are many FDA-approved drugs including prescription and non-prescription for the treatment of head lice infestation but genetic resistance of lice to lindane and to the most commonly used treatments, pyrethroids, is not uncommon in the US. Because of this development of additional drugs for this indication is encouraged, stated the regulator.

According to skin specialist from both the government and private clinics, head lice infestations are a concern and there is a need for new drugs because those affected are forced to change formulations to control the condition.

The purpose of this guidance is to assist sponsors in the clinical development of drugs to treat head lice infestation. It is characterized by infestation of the scalp and scalp hair. The wingless parasitic insect lives on the hair and feeds on the scalp by consuming a blood meal. There are many FDA-approved prescription and non-prescription drugs to treat head lice infestation, but genetic resistance call for development of additional drugs for this indication, noted the regulatory authority in its guidance.
 
In early phase clinical development the components of the investigational drug need to be defined. If two or more active components are identified, it should demonstrate that each should make a contribution to the claimed effects. The combination should be safe and effective for the intended patient population. If the drug contains more than one active ingredient, the sponsor can consider in vitro studies to assess the contribution to efficacy of each of the active ingredients. This issue should be discussed with the Agency early in clinical development, according to the guidance note.
 
Clinical trials to identify an appropriate safe and effective dose are an important component of phase 2 development for topical treatment. A dose-response trial conducted during early phase clinical development to assess safety and efficacy can help ensure that the most appropriate dose regimen is selected for phase 3 development.
 
As per the guidance, during the drug development, the  trial population should be representative of the age, race, and sex with head lice infestation. Paediatric subjects should be evenly distributed across age groups in the US. Inclusion of younger age groups would be dependent upon safety findings for the investigational drug. Geographical diversity is also important for the treatment of head lice infestation because resistance patterns to some drugs vary by location.

If the sponsor plans to conduct trials outside of the US, it should consider factors that may affect the acceptability of such data for drug approval by the regulator. Both local and systemic safety information should be collected during clinical trials. All subjects should be evaluated for safety at the time of each trial visit, regardless of whether the investigational drug has been discontinued for safety. Generally, all adverse events should be followed, even if time on clinical trial would otherwise have been completed, stated the regulator.