HOW OPIATES MOVE THROUGH THE BODY
The rate at which opiates enter the brain depends
mainly on how the user takes them. The
fastest way to get high is to inject the drug directly into the bloodstream. The second fastest is to smoke it.
When opiates are smoked or injected,
peak levels in the brain occur within minutes. Fentanyl is the most
fat-soluble and achieves maximum brain concentrations in seconds. Heroin is a
little slower; it takes a couple of minutes. Morphine is slower still, but not by much (five minutes). The faster the
buzz, the greater the danger of death
by overdose, because drug levels in the brain can rise so quickly. Snorting heroin causes slower absorption because the drug must travel through the mucous
membranes of the nose to the blood
vessels beneath.
After taking a pill, the high is much slower
because the drug must be absorbed from
the small intestine into the bloodstream, then pass through the liver, which can metabolize much of a
dose, before it ever gets into the
circulation. This process takes about thirty minutes, so there's no rush after oral administration. This lack of a
"rush" is why methadone is so
useful in treating addicts, and as a pain medication. Sometimes users figure out how to circumvent opiate preparations
that are designed to have a slow
onset—the formulation of OxyContin provides a now-notorious example. OxyContin is a delayed-release form of
oxycodone that is designed to release
drug gradually, providing pain relief over hours. However, users discovered that crushing the pills
causes a quick release of drug and gives a "high" that the
manufacturer did not intend. Following its
introduction in 1996, OxyContin rapidly gained a reputation as the hot
"new" drug of abuse. It has since been reformulated to make abuse
more difficult.
The duration of action depends upon how quickly
the drug-metabolizing enzymes in the
liver degrade the particular drug. Most of the drugs mentioned last for four to six hours. The exact time can vary from two
hours (morphine) to up to six or so (propoxyphene), but all opiates are pretty similar. There are two important
exceptions. Methadone lasts for twelve
to twenty-four hours, so it can be given as a single daily dose. Fentanyl goes to the other extreme: the effects are
over within an hour.
