Week 1 Flashcards
The WHO model for rational drug prescribing
- Define the patients problem
- Specify the therapeutic objective
- Choose the treatment (determine if it’s right based on evidence based guidelines and individualize for the patient)
- Start the treatment
- Educate the patient
- Monitor the effectiveness (passive- patient calls based on their education. Active- blood levels, adjust dosage, decide whether to continue)
- Define the patients problem
- Specify the therapeutic objective
- Choose the treatment (determine if it’s right based on evidence based guidelines and individualize for the patient)
- Start the treatment
- Educate the patient
- Monitor the effectiveness (passive- patient calls based on their education. Active- blood levels, adjust dosage, decide whether to continue)
The WHO model for rational drug prescribing
Half-life
The time it takes to eliminate 50% of the drug from your body/ plasma.
Ultimately determines how often a drug is administered. Usually not dose-dependent. A patient with renal or hepatic dz may have increased 1/2 life. Takes 4-5 half lives to reach steady state during continuous dosing.
Onset of action
The time it takes from administration to first therapeutic effect
Peak action
The time it takes from administration to maximum therapeutic effect
Duration of action
How long a drug works before it’s out of your system
First-pass metabolism
Metabolism by the liver following PO administration.
Metabolism is the process of changing one chemical into another. Occurs mostly in the smooth ER of the liver. First organ to encounter drugs after they are absorbed by the GI tract, so has a high level of drug metabolizing enzymes.
Steady state
Steady state concentration. If the drug is given regularly, the rate of administration will eventually equal the rate of elimination. Can be predicted by half-life. We want a concentration high enough to be effective but not to high to be toxic. The goal is to reach a steady state concentration within therapeutic range.
Isoenzymes of the P450 system
Cytochrome P450 Isoenzyme
The cytochrome P450 isoenzymes represent a family of more than 30 related heme-containing enzymes, largely located in the endoplasmic reticulum of hepatocytes (but also present elsewhere, including the gut and brain), which mediate oxidative metabolism of a wide variety of drugs, as well as endogenous substances (including prostaglandins, fatty acids, and steroids).
Drug metabolism is when the drug is chemically altered by enzymes into new molecules called metabolites. It can increase or decrease onset, duration of action, and toxicity of a med. Cytochrome (CYP) 450 is a mixed-drug oxidase reaction, which is a type of drug metabolism reaction. It catalyzes the metabolism of a large number of drugs and chemicals that are highly lipid soluble. The different types have different functions in metabolizing drugs. Happens in the metabolism phase. Enzyme induction and enzyme inhibition.
Potency
The concentration needs for the same effect.
Efficacy
The effect of a drug.
The time it takes to eliminate 50% of the drug from your body/ plasma.
Ultimately determines how often a drug is administered. Usually not dose-dependent. A patient with renal or hepatic dz may have increased 1/2 life. Takes 4-5 half lives to reach steady state during continuous dosing.
Half-life
The time it takes from administration to first therapeutic effect
Onset of action
The time it takes from administration to maximum therapeutic effect
Peak action
How long a drug works before it’s out of your system
Duration of action
