Psychostimulants include a broad range of illicit (or illegal) drugs such as amphetamines, methamphetamines, crystal, base and speed.

'Speed' is also a name given to a variety of illicit 'street drugs' that, in chemical terms, are related to amphetamines. These are classed as stimulants (or psycho-stimulants) because they increase central nervous system activity.

They basically speed up the way your brain does things, including making you breathe faster, making your heart beat faster and giving you more energy. They can also boost your confidence or make you feel like you can deal with any situations, including feats of endurance and long periods without sleep.

From the mid 1980s to early 1990s, amphetamine sulphate was made and available locally. This was replaced by methamphetamine (meth) and crystalline methamphetamine (crystal meth) which, in its purest form, is many times more potent (and therefore, potentially more dangerous) than before.

Since the mid 1990s, locally manufactured meth (like speed, goey and whiz) has been based on pseudoephedrine, similar to amphetamine but with an extra methyl molecule - making it more potent.

More recently crystalline methamphetamine (crystal meth) is a high purity meth mostly imported from Southeast Asia. It's also referred to as ice, shabu, crystal or crystal meth. There is some evidence that it's now being made locally.

Base or paste meth is a result of an incomplete (or stuffed up) manufacturing process. Because amphetamines are made illegally, there is no quality control and there is no way you can tell how strong a particular batch is going to be. Likewise, there is no way to tell what has been used to cut the drugs - always a danger.

As with all illicitly manufactured drugs, there is no way of knowing the level of purity (or strength) of the drugs you're going to use and no guarantee that the amount you use is safe. If you do use it's always best to try a small dose first and to be around your mates to look after each other just in case.