Pharmacodynamics - what the drug does to the body
Variation in drug resposne is explained by envirobmental factors and genetic factors
Studies the relationship between the drug concentration and the pt's response to the drug
Involves receptor binding, postreceptor effects, and chemical interactions
Pharmacokinetics - What the body does to the drug (ADME)
Receptor theory requires two properties - Affinity (attraction between a drug and its receptor)
Instrinsic activity (efficacy - ability of the drug to activate a receptor and produce an effect)
Efficacy - maximum effect of a drug regardless of dose
Potency - amount of drug needed to produce an effect
Describes the diff in concentration or dosage of diff drugs required to produce similar effect
More potent = lower dosage required
graded drug response - illustrate the degree of response to the dose. Dose modification will adjust the
physiological response (e.g., B/P, HR, Pain, etc.)
Quantal drug response - all or none (seizures, pregnancy, sleep)
,However we may see a graded response until we achieve the quantal respinse (reducing amount of
seizures until seizure free)
Drug selectivity - The ratio of the dose or concentration producing the undesired effect to the dose
producing the desired effect
Bad/good
Therapeutic index or range - A special ratio describing drug selectivity is the ratio of the lethal
dose/minimum toxic concentration to a therapeutic dose of a drug/minimum effective concentration
Agonist - Binds to the receptor and cause a change in cellular activity
It has both affinity and efficacy
Antagonist - Binds to the receptor and cause no change in cellular activity and blocks the ability of
endogenous substances or other drugs to bind to the receptor. It lack efficacy
Antagonist should never be stopped abruptly why - Exaggerated reponse due to increase number of
receptors
Absorption - the movement of a drug from its site of administration into the bloodstream or systemic
circulation
Distribution - The reversible transfer of a drug from one location to another within the body.
Metabolism - The process by which the body breaks down and converts the drug into active chemical
substances
,Excretion - Processes by which a drug is eliminated from the body
Variables that influence absorption - Nature of the cell membrane
Blood flow at site of administration
Solubility of drug
pH
Molecular weight
Drug concentration
Dosage form
Bioavailability - The percentage of drug that is absorbed and available to reach the target tissue or the
Fraction of unchanged drug reaching the systemic circulation following administration by any route
Onset of action - time between administration and first sign of drug effect
Peak of action - Maximum concentration of drug.
Point at which amount of drug being absorbed and distributed is equal to amount being metabolized
and excreted.
Duration of action - Continued entry of drug into body with levels above minimum effective
concentration
Does speed affect drugs absorption? - Yes - the speed at which drugs enter the bloodstream affects the
max blood levels that is achieved following drug administration
Rapid absorption - quicker response - higher toxicity hence why we dont push dome drugs in IV
, Bioavailability in IV meds - 100%
Bioavailability decreases in which route? - Oral due to incomplete absorption and first-pass metabolism
If bioavailability is low what should the dose be? - High
Ex - ciprofloxacin has 80% bioavailability. thus 400 mg IV dose is equivalent to 500mg PO
Order of bioavailability of oral drugs from high to low? - Solution > suspension > capsule > tablet >
coated tablet
Bioequivalent - Equivalent systemic release of the same drug substance from 2 or more drug products of
formulations
Distribution depends on - adequacy of blood circulation
Molecular size/weight
Balance of lipid to water solubility
Environment - acidity and proteins
In order for drugs to be filtered in kidney - Drugs have to be unbound
pKa - The percentage calculation of charged and uncharged molecules for a drug
Nonionized drugs are - Lipid soluble and readily cross plasma membranes