Medically assisted treatment and drug-free treatment are the two main modalities of treatment related to illegal drug use. Medically assisted treatment is almost exclusively provided in an outpatient setting, whereas drug-free treatment can be given in residential or outpatient settings. In the EU, in practice, only agonists (e.g. methadone) or combined antagonists/agonists (e.g. buprenorphine) are used for long-term treatment, whereas antagonists (e.g. naloxone) may be used in withdrawal treatment.