People who
intravenously inject black tar heroin are at higher risk of venous
sclerosis than those injecting powder heroin. In this condition, the
veins narrow and harden which makes repeated injection there nearly impossible. The presence of
6-monoacetylcodeine found in tar heroin has not been tested in humans but has been shown to be toxic alone and more toxic when mixed with mono- or di- acetyl morphine, potentially making tar more toxic than refined diamorphine. Black tar heroin injectors can be at increased risk of life-threatening bacterial infections, in particular
necrotizing soft tissue infection. The practice of "skin-popping" or subcutaneous injection predisposes to
necrotizing fasciitis or necrotizing
cellulitis from
Clostridium perfringens, while deep intramuscular injection predisposes to necrotizing
myositis. Tar heroin injection can also be associated with
Clostridium botulinum infection, causing
botulism. Since the final stage of black tar heroin production would kill any spores (a combination of high temperature and strong acid), contamination is likely due to choice of cutting agent. Almost all cases occur in users who inject intramuscularly or subcutaneously, rather than injecting intravenously. Black tar heroin users can also be at increased risk of bone and joint infections that stem from
hematogenous seeding or local extension of the skin and soft tissue infections. Any joint can be infected, though previous studies have shown that the knee and hip are most commonly affected in heroin injectors. Associated bone infections can include septic
bursitis, septic
tenosynovitis, and
osteomyelitis.
Septic arthritis and skin and soft tissue infections often present visible and/or systematic symptoms, while
osteomyelitis usually presents localized pain. ==Alternative routes of administration==