There are very few drugs which cannot be injected. Heroin is the best known but all the opioids and opiates can be injected as can the stimulants amphetamines and cocaine and almost any drug which comes in tablet or capsule form. Cannabis is very difficult to inject.
Some drugs come in ampoule form ready for injection either as a liquid or sometimes as a powder to which sterile water can be added.
Other drugs come as tablets or capsules which are then crushed or broken open and the contents mixed with water to make a solution ready for injection. One of the tranquilliser drugs, Temazepam is produced in a gel filled capsule which is sometimes heated by drug injectors prior to injecting the warmed up liquid.
Other drugs, particularly heroin, amphetamine and cocaine are usually supplied as powders of varying consistencies and purities which need to be prepared for injection.
Powders and crushed up tablets need to be prepared by first of all mixing with water. 'Brown' street heroin will also need citric or ascorbic acid to be added in order to help it dissolve. Unless the drug concerned is very pure it will also be necessary to filter out the impurities, chalk and other dust which may be mixed in with the drug.
Injection can be intramuscular (into a muscle), subcutaneous (under the skin), or intravenous (directly into a vein), but the last of these is the preferred route for the majority of drug users. This is because the rapid onset of the drug effect produces an intense rush of exhilaration.
Overdose is an ever constant risk whenever street drugs are being injected. This is due to the variable purity and consequent unknown dosage of illicit street drugs.
The tolerance level will vary from person to person. It will also vary over time. Tolerance rises with repeated exposure to the drug so periods of abstinence will be followed by dramatic reductions in tolerance levels. This is why former drug injectors coming out of prison are at particular risks of overdose the first time they inject after a period of enforced abstinence.
Overdose is also more likely if the user takes more than one depressant drug - alcohol, heroin, methadone, tranquillisers or sleeping tablets - at a time. Mixing depressants and stimulants, such as a combination of heroin and cocaine known as a 'speedball', is also extremely dangerous as the effect is unpredictable and has caused death.
Injection of crushed or dissolved tablets carries its own set of risks. Tablets must be crushed to a very fine powder before they can be mixed with water and injected. Even though the drug held within the tablet may partially dissolve, the tablet itself will not liquefy completely. If tablets are used continually in this way, particles will eventually build up in the bloodstream leading to blocked veins, kidney problems and other complications, such as thrombosis.
Injecting temazepam is particularly dangerous. The gel which holds the drug has to be heated to enable injection of a thinner fluid. Unfortunately it will re-solidify at body temperature and has caused severe blockages in veins, amputations and even deaths amongst injectors. There is no safe way to inject temazepam.
Repeated injection in the same sites can cause damage to skin and veins, leading to ulceration, abscesses and collapsed veins. As finding a vein becomes more difficult injectors may resort to even more dangerous sites such as the fine blood vessels in fingers or toes, or the femoral vein in the groin.
The groin is a particularly dangerous site because of the risk of hitting the femoral artery or femoral nerve the consequences of both being very serious. The search for ever more inaccessible sites increases the possibility of hitting nerves or arteries.
Professionals working with drug injectors advise them that to avoid physical damage their clients should always clean the site with a sterile swab, use the smallest needle possible, and regularly rotate injection sites. This means using a different site on the arm or leg each time. This will allow scar tissue to heal fully.
The risk of infections by blood borne viruses such as hepatitis and HIV is high when using shared and non sterile injection equipment. It is not just the syringe itself which poses dangers but also the spoons, filters, water and other paraphernalia used to make up a drug for injection.
During the year 2000 a batch of heroin which had been contaminated with bacteria caused about 40 deaths in the UK and Ireland. This was a previously unknown danger from street drugs which highlights the risks of infections from drugs produced in uncontrolled illegal 'laboratories'.
A network of needle exchange schemes are available across the UK. These provide drug users with new, sterile equipment. Drug workers also advise those of their clients who cannot get to a needle exchange scheme to make sure that their injection equipment is boiled or cleaned with bleach. For bleach cleaning the needle and syringe are flushed through with concentrated bleach, then cold water, and the process repeated several times.