Opioids are narcotic painkiller drugs that work by blocking the transmission of pain signal to the brain. Opioids are prescribed by doctors due to their analgesic and pain relieving properties. But opioids have strong potential to cause addiction. When abused, it causes a sense of euphoria as it affects the part of brain which causes pleasure. Medications which fall under opioids are morphine, codeine etc. Opioids are broadly classified into four types: Natural, Semi-synthetic, fully synthetic, and endogenous.

Classification:
Natural:
Natural opioids are opiate alkaloids obtained from the resin of the poppy plant. Morphine and codeine are derived from opiate alkaloids. The latex containing opiate alkaloids is obtained from immature opium seeds capsules by making incisions on the walls of green seed pods. This latex is then collected and dried. Drugs like morphine, codeine, thebaine, noscapine, and papaverine are extracted from the dried latex. Opium and opioids are used for medicinal purpose as narcotic analgesics, hypnotics, and sedatives. Although the latex from poppy plant is used to produce morphine, codeine etc but the poppy oil and seeds are not narcotic and put to variety of uses.

Semi-Synthetic:
Semi-synthetic opioids do not occur naturally and are created from natural opiates and share similar chemical structure. Drugs like hydrocodone, oxycodone, oxymorphone, hydromorphone, and diacetylmorphine (heroine) are semi-synthetic opioids derived from natural opiates. The semi-synthetic opioids drugs are used in variety of medicinal purpose for their analgesic properties. Semi-synthetic opioids are also widely abused. However, drug tests testing for presence of ‘opioids’ can not detect semi-synthetic opioids except diacetylmorphine (heroine) as it easily transforms into morphine.

Fully Synthetic:
The fully synthetic opioids are artificially manufactured and are not related to opiates. Some of the drugs that are fully synthetic are methadone, fentanyl, pethidine, tramodol, dextropropoxyphene etc. These drugs are used as analgesic and used to treat chronic pain. Drug like fentanyl is also used to give anesthesia before surgeries and is 100 times stronger than morphine. Apart from its analgesic properties, Methadone is used to treat opioid addiction. Methadone can block the effects of other drugs like heroin, morphine and help to tackle the withdrawal symptoms.

Endogenous:
Endogenous opioids are naturally produced in the body and used as neurotransmitters. The endogenous opioids produced in body include endorphins, enkephalins, dynorphines, and endomorphines. These endogenous opioids regulate the bodily functions like hunger, thirst, mood control, immune response, and reactions to painful stimuli etc. Drugs like morphine and heroine produce strong feeling as they also bind to same receptors to which endogenous opioids also bind.

Opioids are most commonly abused prescription drugs. Opioids should not be used with substances like alcohol, antihistamines, barbiturates, benzodiazepines etc that causes depression of Central Nervous System. A specific test needs to be performed to detect many fully synthetic and semi-synthetic opioids as these drugs will not show up in normal testing.