General Pharmacology Flashcards
Calculation for oral bioavailability
Plasma conc / dose given
Factors affecting oral bioavailability
Lipophilicity, Molecule size, First pass metabolism
Calculation for distribution
Dose given / plasma conc
Compartments the drug is in with a Vd < 0.2
Plasma
Compartments the drug is in with a Vd between 0.2 and 0.7
ECF
Compartments the drug is in with a Vd > 0.7
Whole body (Fat)
Factors affecting volume of distribution
Lipid solubility, DDIs, Protein binding, Diseases
Measure of elimination
Half-life
Calculation for half life
0.693 x Vd / Clearance
Define first order kinetics
Elimination is proportional to dose
Define zero order kinetics
Elimination constant over time
Number of half lives to reach steady state
4-5
Calculation for loading dose
Vd x Desired conc
Define selectivity
Drugs ability to bind to a receptor
Define specificity
Drugs ability to cause a response in a receptor
Define affinity
How readily a drug binds to a receptor
Measure of affinity
Kd
Define Kd
Conc at which 50% of receptors are occupied
Define efficacy
Degree of response from a receptor generated by a drug
Define potency
Dose required to generate a response
Measure of potency
EC50
Define EC50
Conc at which a 50% response is generated
Types of ADRs
On target and off target
Define on target ADRs
Greater than desired effect at target site
Define off target ADRs
Where drug works on an undesired receptor type
Common CYP450 inducers
Phenytoin, Carbamezpine, Barbituates, Rifampacin, Alcoholism, St John’s wort
Common CYP450 inhibitors
Omeprazole, Disulfaram, Erythromycin, Valproate, Isoniazid, Ciprofloxacin, Ethanol, Sulphpnylamide
Common drugs bound to plasma protein
Sulphonylureas, Phenytoin, Valproate, Carbamezepine, NSAIDs, Warafrin, Glitazones, Heparin
