A 2010 study ranking various illegal and legal drugs based on statements by drug-harm experts.<unk>  was found to be the second overall most dangerous drug.<unk>  is classified as a<unk> ard drug in terms of drug<unk> armfulness. Like most opioids, unadulterated<unk>  may lead to adverse effects. The purity of street<unk>  varies greatly, leading to overdoses when the purity is<unk> igher than they expected. Short term effects Short-term effects of usage Users report an intense rush, an acute transcendent state of euphoria, which occurs while diamorphine is being metabolized into 6-monoacetylmorphine (6-MAM) and morphine in the brain. Some believe that<unk>  produces more euphoria than other opioids; one possible explanation is the presence of 6-monoacetylmorphine, a metabolite unique to<unk>  – although a more likely explanation is the rapidity of onset. While other opioids of recreational use produce only morphine,<unk>  also leaves 6-MAM, also a psycho-active metabolite.<unk> owever, this perception is not supported by the results of clinical studies comparing the physiological and subjective effects of injected<unk>  and morphine in individuals formerly addicted to opioids; these subjects showed no preference for one drug over the other. Equipotent injected doses<unk> ad comparable action courses, with no difference in subjects' self-rated feelings of euphoria, ambition, nervousness, relaxation, drowsiness, or sleepiness. The rush is usually accompanied by a warm flushing of the skin, dry mouth, and a<unk> eavy feeling in the extremities. Nausea, vomiting, and severe itching may also occur. After the initial effects, users usually will be drowsy for several<unk> ours; mental function is clouded;<unk> eart function slows, and breathing is also severely slowed, sometimes enough to be life-threatening. Slowed breathing can also lead to coma and permanent brain damage.<unk>  use<unk> as also been associated with myocardial infarction. Long term effects Long-term effects of intravenous usage, including – and indeed primarily because of – the effects of the contaminants common in illegal<unk>  and contaminated needles. Repeated<unk>  use changes the physical structure and physiology of the brain, creating long-term imbalances in neuronal and<unk> ormonal systems that are not easily reversed. Studies<unk> ave shown some deterioration of the brain's white matter due to<unk>  use, which may affect decision-making abilities, the ability to regulate behavior, and responses to stressful situations.<unk>  also produces profound degrees of tolerance and physical dependence. Tolerance occurs when more and more of the drug is required to achieve the same effects. With physical dependence, the body adapts to the presence of the drug, and withdrawal symptoms occur if use is reduced abruptly. Injection Intravenous use of<unk>  (and any other substance) with needles and syringes or other related equipment may lead to: * Contracting blood-borne pathogens such as<unk> IV and<unk> epatitis via the sharing of needles * Contracting bacterial or fungal endocarditis and possibly venous sclerosis *Abscesses * Poisoning from contaminants added to "cut" or dilute<unk>  *Decreased kidney function (nephropathy), although it is not currently known if this is because of adulterants or infectious diseases Withdrawal The withdrawal syndrome from<unk>  may begin within as little as two<unk> ours of discontinuation of the drug;<unk> owever, this time frame can fluctuate with the degree of tolerance as well as the amount of the last consumed dose, and more typically begins within 6–24<unk> ours after cessation. Symptoms may include sweating, malaise, anxiety, depression, akathisia, priapism, extra sensitivity of the genitals in females, general feeling of<unk> eaviness, excessive yawning or sneezing, rhinorrhea, insomnia, cold sweats, chills, severe muscle and bone aches, nausea, vomiting, diarrhea, cramps, watery eyes, fever, cramp-like pains, and involuntary spasms in the limbs (thought to be an origin of the term "kicking the<unk> abit").
Heroin
Cannabis
Cannabis 
Cocaine
Cocaine 
Nicotine
Phencyclidine
Opioid