Heroin does not occur naturally. It is produced by diacetylation of morphine, which leads to a threefold increase in its potency. Its greater lipid solubility allows it to cross the blood-brain barrier more rapidly than morphine, causing a more exaggerated euphoria when the drug is injected. Heroin is converted to morphine in the body, but its effects last about half as long. It is used therapeutically in other countries for the severe pain of cancer.