Does clofazimine (B663) reach Mycobacterium leprae persisting in Schwann cells and endothelial cells of endoneurial blood vessels in peripheral nerves?

Peripheral nerve biopsies from 10 Lepromatous leprosy (LL) patients who were on multidrug treatment (MDT) were investigated by light and electron microscopy. Clofazimine (CLF) has been included as an essential component of MDT, which is the standard WHO regimen for treatment of leprosy. The patients receiving continuous MDT for a long period had viable bacilli in Schwann cells (SCs) of peripheral nerves whereas they had disappeared from the skin. Our ultrastructural observations clearly indicated the presence of CLF crystals in SCs. The crystals were in the form of osmiophilic rods of various shapes and sizes. On the other hand, the blood nerve barrier was clearly noticed in endoneurial blood vessels (EBV), and the barrier seems to play an important role for penetration of antileprosy drugs especially CLF.