What is the best treatment for a patient presenting with worsening pruritic rash and evidence of scabies?

The best treatment for a patient presenting with worsening pruritic rash and evidence of scabies is permethrin. Permethrin, a topical scabicide, is highly effective in eliminating scabies mites and their eggs. It works by disrupting the nervous system of the parasites, leading to their death. For a patient diagnosed with scabies, using permethrin is crucial as it directly addresses the underlying cause of the pruritic rash, providing relief from symptoms and resolving the infestation.

On the other hand, prednisone is a corticosteroid that may help reduce inflammation and itching but does not treat the scabies infestation itself. Montelukast is a leukotriene receptor antagonist primarily used for asthma and allergic rhinitis, and it would not have any effect on scabies. Pimecrolimus is a topical calcineurin inhibitor used for atopic dermatitis, and while it may alleviate itching, it does not target the scabies mites or resolve the underlying infestation. Therefore, permethrin is the most appropriate choice for treating scabies effectively.