Opiates are a class of drugs that are derivatives in the broadest sense of the word of opium. These include two groups of alkaloids, namely phenanthrenes and papaverines. Opiates in the narrower sense of the word are only the phenanthrenes. Opioids are synthetic drugs that are chemically unrelated to the opiates, but act on the same receptors in the central nervous system and have similar clinical effects.
Examples of Phenanthrenes naturally occurring in opium are Morphine and Codeine. Examples of Phenanthrenes from semisynthetic derivatives are Heroin, Hydromorphone, Oxymorphone, Hydrocodone and Oxycodone.
Phenanthrenes which are fully synthetic can be divided again into two groups, namely Phenylheptylamines and Phenylpiperidines. Examples of Phenylheptylamines include Methadone and levomethadyl acetate hydrochloride (LAAM). Examples of Phenylpiperidines include Meperidine, Fentanyl, Alfentanil, Sufentanil, Remifentanil.
Examples of Phenanthrenes from semisynthetic derivatives that are specifically manufactures for veterinary uses include Etorphine and Carfentanyl. In view of the fact that the constitutions of the larger animals, like the elephants, are generally much stronger than that of the human beings, the Phenanthrenes that are used are generally much stronger than those which are not designed for veterinary uses. For example, although Etorphine is semisynthetic derivative of morphine, it has the potency of 10 000 times that of morphine itself.
Opiates generally belong to the group of medicines called narcotic analgesics. Narcotic analgesics are used to relieve pain. Opiates generally act in the central nervous system to relieve pain. Some of its side effects are also caused by actions in the central nervous system.
When a narcotic is used for a long time, it may become habit-forming, causing mental or physical dependence. A high number of opiates are considered to be highly addictive. One exception is loperamide, which cannot cross the blood-brain barrier. However, people who have continuing pain should not let the fear of dependence keep them from using narcotics to relieve their pain. Mental dependence or addiction is not likely to occur when narcotics are used for this purpose.
Physical dependence may lead to withdrawal side effects if treatment is stopped suddenly. However, severe withdrawal side effects can usually be prevented by reducing the dose gradually over a period of time before treatment is stopped completely.
N.B. Cisapride is a medicine that increases the movements or contractions of the stomach and intestines. It is generally used to treat symptoms such as heartburn caused by a backward flow of stomach acid into the esophagus. This medicine could be used in conjunction with opiates to prevent the natural gagging reflexes of the body to purge the opiates, even if taken to an excessive level, to achieve whatever ends there is to achieve.