The therapeutic index varies widely among substances: most forgiving among the opioid analgesics is remifentanyl, which offers a therapeutic index of 33,000:1; tetrahydrocannabinol, a sedative and analgesic of herbal origin (cannabis), has a safe therapeutic index of 1000:1, while diazepam, a benzodiazepine sedative-hypnotic and skeletal muscle relaxant has a less-forgiving index of 100:1 and morphine, a sedative, antidepressant, and analgesic also of herbal origin (genus Papaver) has an index of 70:1[3] (which, however, is still considered very safe).
Less safe are cocaine, a stimulant and local anaesthetic, and ethanol (colloquially, the "alcohol" in alcoholic beverages), a widely available sedative consumed world-wide – the therapeutic indices for these substances are 15:1 and 10:1, respectively.[4] Even less-safe are drugs such as digoxin, a cardiac glycoside; its therapeutic index is approximately 2:1.[5] Other examples of drugs with a narrow therapeutic range, which may require drug monitoring both to achieve therapeutic levels and to minimize toxicity, include: paracetamol (acetaminophen),