Drug injection taking drugs, injection is favoured by some people as the full effects of the drug are experienced very quickly, typically in five to ten seconds. It also bypasses first-pass metabolism in the liver, resulting in higher bioavailability and efficiency for many drugs (such as morphine or diacetylmorphine/heroin; roughly two-thirds of which is destroyed in the liver when consumed orally) than oral ingestion would. The effect is that the person gets a stronger (yet shorter-acting) effect from the same amount of the drug. Drug injection is therefore often related to substance dependence. In a recreational context, the shorter, more intense "high"
Center for Drug Evaluation and Research new drugs on healthy volunteers in small groups to determine the maximum safe dosage. Phase II trials involve patients with the condition the drug is intended to treat to test for safety and minimal efficacy in a somewhat larger group of people. Phase III trials involve one to five thousand patients to determine whether the drug is effective in treating the condition it is intended to be used for. After this stage, a new drug application is submitted. If the drug is approved, stage IV trials are conducted after marketing to ensure there are no adverse effects or long term