Narcotic

# Background
The term narcotic () is believed to have been coined by Galen to refer to agents that benumb or deaden, causing loss of feeling or paralysis.  The term is based on the Greek word  (narcosis), the term used by Hippocrates for the process of benumbing or the benumbed state.  Galen listed mandrake root, altercus (eclata) seeds, and poppy juice (i.e. opium) as the chief examples.
In U.S. legal context, narcotic refers to opium, opium derivatives, and their semi-synthetic or fully synthetic substitutes "as well as cocaine and coca leaves," which although classified as "narcotics" in the U.S. Controlled Substances Act (CSA), are chemically not narcotics. Contrary to popular belief, marijuana is not a narcotic. Neither are LSD and other psychedelic drugs.
Many law enforcement officials in the United States inaccurately use the word "narcotic" to refer to any illegal drug or any unlawfully possessed drug.  An example is referring to cannabis as a narcotic.  Because the term is often used broadly, inaccurately or pejoratively outside medical contexts, most medical professionals prefer the more precise term opioid, which refers to natural, semi-synthetic and synthetic substances that behave pharmacologically like morphine, the primary active constituent of natural opium poppy.

# Administration
Narcotics can be administered in a variety of ways. In a medical context, they are taken orally, transdermally (skin patches), injected, or administered as suppositories. As recreational drugs, they may be used orally, but are also commonly smoked, snorted, or self-administered by the more direct routes of subcutaneous ("skin popping") and intravenous ("mainlining") injection, depending on the precise substance in question. (Recreational use of suppositories is uncommon.)

# Effects
Drug effects depend heavily on the dose, route of administration, previous exposure to the drug, and the expectation of the user. Aside from their clinical use in the treatment of pain, cough, and acute diarrhea, narcotics produce a general sense of well-being, known as euphoria, and reduce tension, anxiety, and aggression. These effects are helpful in a therapeutic setting and contribute to their popularity as recreational drugs, as well as helping to produce dependency.
Narcotic use is associated with a variety of side effects, including drowsiness, itching, sleeplessness, inability to concentrate, apathy, lessened physical activity, constriction of the pupils, dilation of the subcutaneous blood vessels causing flushing of the face and neck, constipation, nausea, vomiting and, most significantly, respiratory depression. As the dose is increased, the subjective, analgesic, and toxic effects become more pronounced. Except in cases of acute intoxication, there is no loss of motor coordination or slurred speech, as occurs with many depressants such as alcohol or barbiturates.

# Hazards
Among the hazards of careless or excessive drug use are the increasing risk of infection, disease and overdose. Medical complications common among recreational narcotic users arise primarily from the non-sterile practices of injecting. Skin, lung and brain abscesses, endocarditis, hepatitis and HIV/AIDS are commonly found among persons with narcotic dependencies who share syringes or inhale the drug. There has been much discussion about the dangers related to the adulterants/diluents found in street drugs, such as heroin, where rumours abound about what is used to "cut" street drugs, e.g., ground glass, talcum powder, rat poison, domestic cleaning powders, and other cutting agents. Recent evidence shows that this kind of "dangerous adulteration" is largely mythical and that far less cutting of drugs than is normally assumed actually takes place. However, since there is no simple way to determine the purity of a drug that is sold on the street, the effects of using street narcotics are unpredictable. It remains the case that the greatest risk presented by most illicit drugs relates to the drugs themselves and how they are used, e.g., in conjunction with other drugs (alcohol is a particularly risky drug to use whilst also using other street drugs), in excess (most recreational and non-excessive drug use does not result in harm), and how a drug is administered (such as the sharing of needles).  HIV and hepatitis  infection rates drop among opioid injectors who have access to clean syringes and take advantage of that provision.

# Tolerance and dependence
With repeated use of narcotics, tolerance and dependence develop. The development of tolerance is characterized by a shortened duration and a decreased intensity of analgesia, euphoria and sedation, which creates the need to administer progressively larger doses to attain the desired effect. Tolerance does not develop uniformly for all actions of these drugs, giving rise to a number of toxic effects. Although the lethal dose is increased significantly in tolerant users, there is always a dose at which death can occur from respiratory depression. It is clear, however, that tolerance and dependence, both part of the conventional idea of addiction, are insufficient to explain in totality what addiction is. Addiction is a broader behavioural phenomenon that also encapsulates nonsubstance based activity (such as excessive and compulsive gambling, excessive and compulsive eating, and a range of other excessive and compulsive behaviours) that has many of the same characteristics that substance based dependency displays.  Moreover, it isn't always the case that those with a physical dependency to opiates find it too difficult to get over their "addiction," because so-called medical addicts (those that become physically dependent on opiates given for pain relief after treatment) only have to "give-up" the physical symptoms - they don't also have the all important psychological and life-style attachment to the drug which goes to make up the all-encompassing "addiction."
Physical dependence refers to an alteration of normal body functions that necessitates the continued presence of a drug in order to prevent the withdrawal or abstinence syndrome. The intensity and character of the physical symptoms experienced during withdrawal are directly related to the particular drug in use, the total daily dose, the interval between doses, the duration of use and the health and personality of the user. In general, narcotics with shorter durations of action tend to produce shorter, more intense withdrawal symptoms, while drugs that produce longer narcotic effects have prolonged symptoms that tend to be less severe.
The withdrawal symptoms experienced from opioid addiction are usually first felt shortly before the time of the next scheduled dose. Early symptoms include watery eyes, runny nose, yawning and sweating. Restlessness, irritability, loss of appetite, tremors and severe sneezing appear as the syndrome progresses. Severe depression and vomiting are not uncommon. The heart rate and blood pressure are elevated. Chills alternating with flushing and excessive sweating are also characteristic symptoms. Pains in the bones and muscles of the back and extremities occur as do muscle spasms and kicking movements, which may be the source of the expression "kicking the habit." At any point during this process, a suitable dose of any opioid can be administered that will dramatically reverse the withdrawal symptoms. Without intervention, the syndrome will run its course and most of the overt physical symptoms will disappear within 5 to 15 days, depending on the opioid used.
The psychological dependence that is associated with narcotic addiction is complex and protracted. Long after the physical need for the drug has passed, the addict may continue to think and talk about the use of drugs. There is a high probability that relapse will occur after narcotic withdrawal when neither the physical environment nor the behavioral motivators that contributed to the abuse have been altered.
There are two major patterns of narcotic dependence seen in the United States. One involves individuals whose drug use was initiated within the context of medical treatment who escalate their dose through "doctor shopping" or branch out to illicit drugs. A very small percentage of addicts are in this group.
The other more common pattern of non-medical use is initiated outside the therapeutic setting with experimental or recreational use of narcotics. The majority of individuals in this category may use narcotics sporadically for months or even years. These occasional users are called "chippers." Although they are neither tolerant of nor dependent on narcotics, the social, medical and legal consequences of their behavior can be very serious. Some experimental users will escalate their narcotic use and will eventually become dependent, both physically and psychologically. The earlier drug use begins, the more likely it is to progress to dependence. Heroin use among males in inner cities is generally initiated in adolescence, and dependence often develops in about 1 or 2 years.
Signs and symptoms of narcotic/opioid overdose include the following:  euphoria, arousable somnolence ("nodding"), nausea, pinpoint pupils (except with Pethidine/Meperidine ), hypoxia, or in combination with other types of drugs, coma, and seizures.