What is the recommended treatment for extensive scabies if topical treatment fails?

When topical treatment for extensive scabies fails, the recommended treatment is oral ivermectin. Oral ivermectin is effective in treating scabies, particularly in cases involving crusted (Norwegian) scabies or widespread infestations that are not adequately addressed by topical therapies. It works by disrupting the nerve and muscle function of the scabies mite, leading to its death.

In cases where patients present with extensive scabies, especially those that may involve large areas of the body or in immunocompromised individuals, oral ivermectin provides a systemic approach that can be more effective than topical agents. It also allows for easier application and better compliance, as it involves a single oral dose followed by another dose one to two weeks later, rather than requiring frequent applications of topical agents.

Topical treatments like permethrin and sulfur ointments are effective for standard scabies infestations but may not be sufficient for extensive cases where the infestation has persisted despite adequate application. Thus, oral ivermectin becomes the preferred choice in such situations.