The powerful painkiller pethidine is usually used when a person is giving birth, but during his six months in the OB/GYN wing of the medical center, Harold Shipman used the drug (via The Guardian). He routinely wrote prescriptions for patients that he would then fill for himself. Shipman would give some medicine to his patient, but keep the leftover pethidine, which he then injected into his arms or legs. Other times, he would take the entire pethidine dose, meant for someone who was in labor, and consume it himself. He prescribed doses large enough to raise the eyebrows of those around him.

By the end of his time on the OB/GYN ward, he was completely dependent on the substance, according to the Shipman Report. Shipman started to have blackouts, per TruTV, but he told his colleagues that epilepsy was to blame. His place of business had caught on to his habit of overprescribing drugs, and Shipman entered drug rehabilitation in 1975.

Shipman wasn’t able to stay away from pethidine, according to The Guardian. In 1976, he was convicted on forgery charges — he had been writing forged prescriptions for huge doses of the drug again. The same year, Shipman got access to a dose of morphine strong enough to kill 360 people. Although he would inject some of the pain medicines into himself, he was also killing his patients with the same chemicals, causing diamorphine overdoses.

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