Pharmacokinetics of Illicit Drugs

Pharmacokinetics is a branch of pharmacology that studies the movement of drugs through the system. The acronym ADME is often used in pharmacokinetics to describe the four parts of a drugs journey through the body: Absorption, Distribution, Metabolism, and Excretion. The principles of pharmacokinetics are often applied to make sure the appropriate formulation of a drug is prescribed for the appropriate route of administration. For example, a drug that needs to be broken down by the liver should never be prescribed as an injection drug because injection bypasses the liver breakdown process.

Pharmacokinetics: Why would drug addicts care?

As a pharmacy student, I was forced to study and understand the pharmacokinetic properties of many, many drugs. It was mind-numbing. If I didn’t also happen to be a drug addict, I probably wouldn’t understand why anyone would want to study pharmacokinetics on their own.

However, in my addiction I found I WAS interested in the pharmacokinetics of certain drugs, mostly prescription narcotics. Drug users are want to know, for example, which routes of administration (swallowing, snorting, injecting, smoking) will result in a better high. For some drugs-like Suboxone, Codeine, and Hydrocodone, snorting or injecting the drug will cause the drug to lose some or all of its potency.

Pharmacokinetics: What properties do addictive drugs share?

In general, highly addictive drugs have the following pharmacokinetic properties: rapid absorption, rapid entry into the central nervous system, high bioavailability, short half-life, small volume of distribution and high free drug clearance. It is this process that allows a high concentration of the active drug in your blood stream in a short amount of time. Experts agree that drugs with this kind of pharmacokinetics have the highest risk of dependency. The user gets a fast, intense high, followed by a “come-down” that leaves the brain craving more.

In general, smoking and intravenous routes tend to show similar onset and bioavailability, and these two routes of administration have the fastest onset and the highest bioavailability (amount of active drug in the blood stream).However, this is not always the case, particularly when the drug must undergo first-pass metabolism in the liver to become active, or when the drug is compounded with other medications. For example, Suboxone is a formulation of buprenorphine (an opiate) that contains naloxone (an opiate blocker). When the drug is taken appropriately (sublingually) the naloxone is deactivated by the liver, and the user gets the full effect of the opiate. If the drug is injected, the naloxone will block the effect of the naloxone. It is also not advisable to inject or snort formulations containing non-narcotic painkillers (Like Percocet).

Snorting can sometimes cause a more rapid onset of the drug (depending on the drugs absorption through nasal membranes) and sometimes (but not always) has a higher bioavailability than swallowing. Swallowing generally has the slowest onset and the lowest bioavailability, but again, it all depends on the pharmacokinetics of the drug. Shooting, snorting, or smoking Vicoden is not effective; the drug can only be taken orally.

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*This is an informational based article and is not intended to replace the advice or knowledge of a medical professional.*