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Lecture 1 - Pharmacokinetics.docx

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PSYC 3403
Tarry Ahuja

Lecture 1 - Pharmacokinetics Pharmacokinetics: How Drugs Are Handled By The Body Chapter 1 Lecture 1 – Jan 8, 2014 Assignment: 2-3 recent journal articles for info (2010 or newer). Must have th a clear take home message including support groups. March 7 due Focus on a drugs specifically, not food, steroids, sex or gambling. Done as an abstract style not a brochure. Simply summarizes all of the info in the article in one little paragraph. - Understand broad concepts and principles Overview • drug distribution • termination of drug action • time course of drug distribution (half-life) • drug tolerance and dependence • drug absorption/administration Pharmacokinetics in Greek: "pharmacon" means drug and "kinetikos" means putting in motion, the study of time dependency Pharmacokinetics: is the time course of a particular drug’s actions - We need to know when something was consumed and how long it lasts in order to know when to take another dose - Could be based on the molecular structure or human intervention that dictates how long it lasts - • absorption - • distribution - • metabolism: how long it takes for you to break it down - • elimination: how long it takes to be expelled from the body Prescription drugs are the most abused drug currently this year. Pharmacokinetics (cont’d) Lecture 1 - Pharmacokinetics Therapeutic Range Minimally effective concentration Chemotherapy plasma concentration Cmax = Maximum concentration Cmin = Minimum concentration Minimally Effective Concentration = The point that is therapeutic, but doesn’t deal with all of the symptoms (or all of the way) ie. Only took 1 advil for a headache and it helps allieve the symptoms enough to start your day, but you can still feel the headache when someone yells or if you bend over. nd Then you take a 2 one that puts you in the therapeutic range. Toxicity Level: Point that pushes you over the edge and makes you violently ill or kills you “overdose” Pharmacokinetics (cont’d) Lecture 1 - Pharmacokinetics • lorazepam (24 hrs) vs. triazolam (8 hrs) - Triazolam is the better choice for sleeping as it doesn’t last all day/night. But you want lorazepam for something like anxiety because it covers you for 24 hours instead of taking multiple doses. Administration Enteral (anything going through your mouth or to your stomach) • oral administration (mouth) • rectal administration (suppository) Parenteral (inhaled or absorbed) • administration by inhalation (lungs) • administration through mucous membranes (nose/mouth) • administration through the skin (patch) • administration by injection (i.v., muscle, skin) Administration (oral) • must be G.I. resistant (G.I. = GastroIntestronal) - Very acidic, If it is not resistant it is just destroyed by the acids and nothing is gained by taking the pill - Not all 100mg of advil actually gets absorbed into the bloodstream, part of it is destroyed by the acid. How much is absorbed depends on the person hence the difference in needing only 1 vs 2 pills Lecture 1 - Pharmacokinetics • liquid vs. tablet/capsule - Liquid is faster. Why? Because your body is mostly liquid so it absorbs liquids faster than needing to break down - In reality it’s a matter of 10-15 minutes - Generic over Name brand? Buy generic as it is the same molecular structure and undergoes the same testing as name brand. You only get a certain percentage of a drug in each pill in a generic. So you may get 80-120% of the drug, you save money on generic and get potentially less drug (or maybe more). In the case of serious medications (ie heart, mood), for this reason you want name brand as the percentage of drug is monitored. • passive diffusion - Think of when a kid pees in the pool and the colour spreads from the dye. Passive means it does not doing anything actively. • lipid solubility - Lipid refers to fat. It is the barrier between the drug getting from the stomach to theblood. If it is lipid soluble it can easily go through the lipid membrane. Disadvantages • vomiting, stomach discomfort (minor side effects) - Why? Because its not natural and is going through your GI system • variable levels of absorption - Comes back to lipid solubility. The rate of how fast/slow a drug gets into your bloodstream is based on the layers of fat the drug has to go through - If you have high levels of enzymes dedicated to a certain drug you will have a harder time with a drug because it destroys the drug faster than it can go through the lipid and be effective (again explaining the difference between needing 1, 2 or 3 pills) • insult from stomach acids Administration (rectal) • delivered in suppository • used in restricted conditions - Ie. Easier to administer to a seizure victim Disadvantages • poor absorption parameters Lecture 1 - Pharmacokinetics - Not made to absorb things! - But it still works as there is a lot of blood supply in that area • rectal membrane irritation Administration (inhalation) • rapid exchange between lung and blood - Ie. Consider smoking. First puff and you almost instantly feel the head rush. - It diffuses through your lungs into your bloodstream and up to your brain. All faster than you can read how it happens. • rapid delivery to brain • used for anesthetic gases Administration (mucous membrane) • administered through nose/Mouth • absorbed through mucosal membrane directly into bloodstream - Wet surface • sublingual administration - Below the tongue • includes: cocaine, nitroglycerine, nicotine gum - When you snort cocaine, it sticks to the lining of your nose and gets diffused into the blood. This is how you get the cocaine to
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