Dr Kerryn Phelps, Health Editor, with Tracey Grimshaw, Channel Nine, 'Today'

PHELPS: Morning, Tracey.

GRIMSHAW: Let's start with cocaine, which is still probably the party drug of choice, of lots of people. How does it work?

PHELPS: Well, it was originally developed as an anaesthetic for medical use in eye, and ear, nose and throat surgery, and still has a limited application there. And it is, to an extent when it's used locally, an anaesthetic, and that's why if somebody rubs it on their gums, or their tongue, they'll get a numb sensation. But, the way it works is that it is usually snorted into the nose, and it has an effect on the brain, and it makes people feel… it has some positive and negative effects. If you look at the positive effects of cocaine, this is the reason people take it, they feel awake, alert, exhilarated. They feel confident, they feel well, they feel that they are strong, that they have greater mental capacity, and that they are more generally aroused, and awake. But, unfortunately with the upside comes the downside. And there are negative effects of cocaine, and it's actually quiet rapidly addictive if you use enough of it over a short period of time you can become quite rapidly addicted. But, also, some people will have a reaction to it where they get very anxious, and get into a panic attack, their concentration, and their judgement goes off, rather than them having great mental capacity, it's the opposite. They can be unpredictable, or violent, very agitated. They can become paranoid, have hallucinations, and also there can be effects on the heart, which can in fact, in people who are prone to it, cause a heart attack.

GRIMSHAW: Can you overdose?

PHELPS: Yes, you can. You can take too much of it, and particularly, if they inhale the fumes of cocaine, called 'free-basing', then that can be very dangerous, and can be fatal.

GRIMSHAW: Is there a rough formula for how much is an overdose, and what's a dangerous amount to use?

PHELPS: Well, it's hard to tell, because when you buy the drug on the street you don't know how pure it is. It can be cut with other substances, and those other substances can cause problems as well.

GRIMSHAW: On the issue of purity, let's go to ecstasy now, because how does anyone know what is in that pill, that they buy?

PHELPS: Well, the simple answer is that you don't. The substances that are used to make ecstasy, the basic substance MDMA, is difficult to find, and quite often other drugs are used to cut the ecstasy or to substitute for it. And, so, it can be very difficult to know exactly what people are buying on the street, because you buy a pill and you're not going to know where it's been made, if it's been made in a backyard laboratory somewhere, imported from overseas - you've got know idea.

GRIMSHAW: Positives and negatives, on ecstasy?

PHELPS: Well, the reason that people take ecstasy is it makes them feel fabulous. Increased confidence, feelings of wellbeing, it's called a 'love' drug because they want to be sort of loving and close to everybody around them, whether they have met them or not. And a certain sort of 'floaty' sensation. But, once again, with the positive comes the negative, and the negative can be pretty ugly as well, and the come down can be nasty. People can feel very depressed, exhausted for a few days, they can even have convulsions, vomiting, irrational or bizarre behaviour. Once again difficult side effects like nausea, and anxiety, sweating, grinding of your teeth and clenching of the jaw, and it can feel very unpleasant. In fact, the interesting thing about ecstasy is that the longer you use it, the less likely you are to get the positive effects, and the more likely you are to get the negative effects.

GRIMSHAW: Okay. Which I suppose makes you use it more, doesn't it?

PHELPS: Research with ecstasy is also showing that long term, there could be some permanent damage to the brain which leads to long term depression.

GRIMSHAW: Okay let's get on to cannabis, because cannabis has been linked to schizophrenia and psychosis, hasn't it?

PHELPS: The real worry with cannabis is that it is being increasingly used by young people. It used to be more used by males than females, the girls have now caught up, and by about the age of 17 or 18 there is about 40 percent of kids, that have actually tried it. Across the board, in Australia, about 40 percent of Australians have used it, occasionally, some use it all the time.

GRIMSHAW: How do we reconcile the positives and the negatives of cannabis? Because, on the one hand, it does have these negative implications. On the other hand, it is used as a therapy drug for pain relief?

PHELPS: People can feel very confident with cannabis, they can feel euphoric, very relaxed, quite often a heightened perception of senses, that's quite often subjective, because people feel that they might have very profound insights into life, and if they were actually played back what they were saying is not actually that profound at all. There is also the negative effects of disassociation of ideas, trouble with concentration, and memory, particularly with young people, long-term. You see, this problem with being able to think clearly in the long term, and that causes problems with their intellectual development, their education. But, also, if someone is prone to psychosis it can trigger that psychosis, and that's a real worry with cannabis.

GRIMSHAW: I wanted to get onto treatment programs, but I think we'll save that for another day. Thanks, Kerryn.

PHELPS: Thanks, Tracey.

Ends