pharm principles Flashcards
Pharmacokinetics
-absorption
-distribution
-metabolism
-excretion
-absorption: movement of drug from site of entry into the systemic circulation
a. bioavailability
b. affected by cell membranes, blood flow, drug solubility, GI tract variability, drug concentration, dosage form, route of administration
-distribution: movement of drug into body fluids and body tissues
a. affected by: permeability of capillaries and tissues, size of drug molecule, affinity for lipid, protein binding
b. plasma protein binding: attach to proteins (mainly albumin), in the blood
c. BBB affects drug distribution: passive transport is limited; drug must be highly LIPOPHILIC to pass into brain
d. half life: time it takes for plasma concentration to be reduced by 50%; determines steady state, dosage interval
-metabolism: chemical inactivation of drug by conversion to a more water-soluble compound (metabolite)
a. hepatic first-pass effect: orally administered drug goes from GI tract through portal system to liver before general circulation; can decrease bioavailability
b. variations in drug METABOLISM can be impacted by genetics, age, pregnancy, liver, disease, diet
c. Prodrugs: drug that must be metabolized to become effective (active metabolites: ex. valcyclovir’s active metabolite is acyclovir); developed to increase absorption, or prolong duration of drug activity
-excretion
a. removal of drug from body via kidneys, intestines, sweat, salivary glands, lungs
pharmacokinetic changes during pregnancy
1. absorption- not significantly affected; A+
- distribution
-plasma volume, plasma proteins - metabolism
-hepatic enzyme systems - excretion
-GFR
- distribution
-increased plasma volume may result in lower serum levels of drug
-reduction in plasma proteins (albumin) may result in higher levels of free drug - metabolism
-hepatic enzyme systems are affected by increasing E + P, may results in faster or slower metabolism of some drug
-NO CHANGE IN FIRST PASS - excretion
-GFR increases which may result in faster elimination of drugs excreted primarily through the kidneys
drug receptors
-agonist
-antagonist
agonist: drug combines with receptor to stimulate a response
antagonist: drug INTERFERES with receptor action or with other drug agonists present
therapeutic index
-the higher the TI…
the safer the drug!
poor vs rapid metabolizer
POOR: may have elevated plasma concentration and are at greater risk of toxicity; may not be able to convert prodrug into active metabolite
RAPID: may have difficulty maintaining therapeutic drug levels; may have increased conversion of prodrug to active metabolite with increased risk of toxicity
pharmacodynamic processes affected by genetics may occur at the drug receptor level affecting…
drug response
-independent from genetic variations in drug metabolism
adverse reactions are…
unintended, undesired effects of drug
predictable vs unpredictable (drug allergy, tolerance)
T/F age-related decreases in METABOLISM and EXCReTION of drugs may result in increased plasma concentration
TRUE
increased risk for ADRS
drugs to avoid when possible with elderly patients includes…
- long acting NSAIDs: increased GI upset
- benzodiazepines: increased risk for falls and confusion; long half life
- drug with anticholinergic effects (amitriptyline, dicylomine, oxybutynin)
- muscle relaxants
- certain diabetes medications like sulfonylureas
Metronidazole
-use
USE: trich, BV, PID
most often given PO (90% bioavailable)
bactericidal
SE: metallic taste, N/V/GI
Disulfiram reaction: acute psychosis and confusion if -metro taken within 2 weeks of disulfiram
-alcohol: may cause N/V
-Cimetidine: can decrease hepatic metabolism of metronidazole and increase serum levels
-can potentiate action of Warfarin
EDU: take with food to decrease GI irritation, avoid alcohol for 48 hours after last dose, may darken urine
Fluconazole
-use
USE: yeast infections
-rapidly absorbed and widely distributed in body tissues and fluids; vaginal, saliva, sputum concentrations about 10x that of plasma; half life: 30 hours
-do not use in pregnancy, instead a topical azole for 7 days is recommended
acyclovir
-use
USE: herpes!
-poorly absorbed, widely distributed; 90% in urine as unchanged drug; only effective against rapidly replicating herpes virus; does NOT eliminate latent virus
-may use to treat first episode of genital herpes in pregnancy or for suppression
EDU: take with water
(NOTE: valacyclovir is prodrug that is converted to acyclovir; better bioavailability and less frequent dosing)
alendronate
-bisphosphonate
-use
-used for prevention and treatment of osteoporosis in postmenopausal women
-low bioavailability especially when taken with food
SE: upper GI irritation, esophagitis
antacids reduce absorption
EDU: must sit uprigth 30 minutes following dose, take in morning with 8 ounces of water, do not eat food, drink fluids or take other meds for at least 30-60 minutes
oxybutynin
-anticholinergic, antimuscarinic
-treats overactive bladder
-rapid absorption and distribution
-SE: dry mouth, blurred vision, constipation, tachycardia, urinary retention
EDU: take wit full glass of water, w or w/o food
Atorvostatin
HMG-CoA reductase inhibitor
-first line in treatment of reducing LDL levels
-extensive first pass effect, low bioavailability
-SE: muscle pain and soreness, Rhabdo (RARE: check creatine kinase levels if significant muscle pain), GI effects
DO NOT USE IN PREGNANCY OR BF
EDU: report unexplained muscle pain
