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Basic Pharmacology


Pharmacology is the study of drugs and their effects on the body, as well as how they are metabolized in the body.

Drugs can be metabolized in two different areas of the body, the kidneys and the liver.  Drugs can be removed from the body in the urine, feces, and breath.

The two most important thing for the average person to consider are absorption and half-life.

Absorption

This is how a drug is brought into the blood stream.  Typical routes of absorption are through the stomach, skin, lungs, intravenous, subcutaneously, and intramuscularly.  All of these routes have different rates of absorption.  The most consistent routes are IV and IM.  Why is this?  IV is easy.  The drugs are injected directly into the blood supply.  IM is next best, as the muscle has very defined blood supply.  SubQ is more variable, as the SubQ space has less predictable blood supply, especially if the person is old and/or obese.  The stomach is not completely reliable, as many people are on drugs that change the acid level in their stomach or have stomach issues such as gluten allergies or irritable bowel syndrome.

All of these areas take different amounts of time for the drug to absorb and take effect.  Even the IV route can be somewhat variable depending on the person’s age.  IV drugs act faster in younger patients.  But, an IV drug will usually produce an effect in less than 2 minutes.  An IM injection should start producing an effect within 5 to 10 minutes.  SubQ and GI routes can take 30 to 40 minutes, sometimes longer, with a peak usually at an hour.  The respiratory route can be fast as well, usually 3 to 5 minutes depending on the drug.

So, if a person injects one drug and takes another drug by mouth, they will see an immediate result from the IV drug, but the pill they took may not do anything for an hour.

Half-Life

This is how long a drug has an effect.  This happens all the time when different narcotics are given to patients for pain control.  One narcotic is fentanyl.  Its effect lasts about one hour.  Morphine lasts about four hours.  They both produce the same effect, pain control, but the duration is much different.  One pain pill, oxycodone lasts for about 3 to 4 hours, while the long acting form of it, oxycontin, lasts for 10 to 12 hours.   Sedatives such as Xanax and Valium have different half-lives as well, even though they are in the same class of drugs.  Xanax lasts for about 4 hours, while Valium can last for 6 to 8 hours.

Stimulants such as Adderal and Ritalin have different versions.  The basic version lasts about 4 to 6 hours, while the extended release can last 12 hours.  How do you know which one the guy behind the gas station sold you?  You really don’t.  It is somewhat like the story in the Hangover movie, where Zach thought he was buying Ecstasy, but actually bought Rufi’s.

Why is all this important?  If somebody takes a bunch of sedatives or narcotics and gets sleepy, then they take Adderal to pick themselves up, then they drink alcohol.  If the narcotics had a long half-life, such as oxycontin and the adderal was the basic version, the adderal will wear off before the narcotics.  The addition of the alcohol at the end, to help get them to sleep because they are jittery from the tail end of the adderal, could be enough to make them stop breathing once the adderal wears off.

Pharmacology is very complex and recreational polypharmacy can have disastrous results in the hands of amateurs.  Conrad Murray was an amateur anesthesiologist and it did not work out so well for Michael Jackson.  When dealing with young, healthy people, it is possible to skate by a number of times, but eventually bad things can happen.