Define and describe the Pharmacodynamic Phase of drug action; including onset, peak and duration of action; receptors; therapeutic index and range; and peak and trough levels.
the effects of the drug on cellular physiology, biochemistry and the drugs mechanism of action. it can have a primary and secondary physiologic effect, or both. the primary effect is desirable; the secondary effect may be desirable or undesirable.
Onset-the time it takes to reach the minimum effective concentration (MEC) after the drug is administered
Peak-occurs when the drug reaches its highest blood plasma concentration
Duration of action- the length of time the drug has a pharmacologic effect
Receptors- are found on the glycocalyx of cell membranes; there are 4 types: 1. cell membrane w embedded enzymes; 2. ligand gated ion channels; 3. G protein-coupled receptor systems; 4. transcription factors
Therapeutic index- (TI) estimates the margin of safety of a drug using a ratio that measures the effective dose and the legal dose to attain a range of safe doses.
Therapeutic Range- a drug concentration in plasma should be b/t the MEC in the plasma for obtaining desired drug action and the minimum toxic concentration (MTC), the toxic effect.
Peak Drug Level- the highest plasma concentration of a drug at a specific time. normally 30 mins after it is administered
Trough Drug Level- the lowest plasma concentration of a drug and measures the rate at which a drug is eliminated. tested 0-15 minutes prior to the next dose.