Quinacrine is an old drug, originally used to treat malaria in the Second World War.
A pair of US doctors discovered that it also caused scarring of tissue, and thought of using it as for sterilization. The technique consists of inserting several small pills into the top of the uterus. There they dissolve, creating scar tissue in the upper womb and nearby fallopian tubes which should block the fallopian tubes and thus prevent conception. It can be performed by paramedical staff. No two women respond identically to the drug, making it hard to design a 'good' dosage.