Pharmacology Flashcards
Xenobiotic
Foreign to body
Phase I Metabolism - 3 jobs
To render lipophilic molecules more polar/hydrophilic, provide functional groups, and enzymatic oxidation, reduction, hydrolysis
Cyp 450s
principally responsible for phase I; most expressed in liver; Cyp1A2, Cyp2C9, Cyp2C19, Cyp2D6, Cyp3A4; most abundant is Cyp3A4; increased activity induced by many drug and chemicals; previous exposures to chemicals can dramatically later drug metabolism; acute or chronic use of one drug can alter metabolism of other drugs in a patient
Induction of Cyp 450
induced by nuclear receptors - examples include Aryl Hydrocarbon Receptor with ligands PAHs, caffeine; constitutive Androstanol Receptor with ligands rifampicin, warfarin; prengenolone X Receptor with ligand simvastatin
Phase II metabolism - job
involves conjugation of Phase I metabolites to large polar molecules
Glucuronidation
Most common phase II conjugation reaction; occurs in liver by UDP-GT enzyme - low activity at birth, rises linearly, and plateaus in adulthood, declines in old age
Clinical Manifestations of low Glucuronidation (3)
Neonatal hyperbilirubinemia - inability of newborn (esp. premature) to metabolize ilirubin - CNS damage due to buildup of bilirubin
Chloramphenicol (antibiotic) - deficiency in UDP-GT, excessive free drug in blood and tissues and drug associated toxcities
Crigler-Naijar Syndrome - almost total genetic deficiency in hepatic UDP-T babies are highly jaundiced, death occurs in early childhood
Beta Glucuronidate
present in mucosa of SI; hydrolyzes glucuronate conjugates, releasing free drug reabsorbed by GI - hepatic circulation of drug which prolongs retention time and biological effects
Phase II Conjugation Reaction
Sulfate conjugation; glutathione S-transferases; Methyl Conjugation; amino acid conjugation; N-acetylation conjugation (some are slow acetylators and some are fast
Factors influencing Drug Metabolism
Genetic factors; sex differences (not much in humans); Disease states; drugs and duration (EtOH - acute intake inhibits drug metabolism while chronic intake increases it); developmental age; nutrition
Nutritional Effects on Drug metabolism (3 of them)
Brussel sprouts, cabbage, cauliflower, dark green inducers of P450 - have potent inducers of P450
Grapefruit Juice - inhibits Cyp3A4 metabolism and increase bioavailability and toxicity of meds
Charcoal broiled beef diet induces AHR
Drug Transporters
ABC (ATP BInding Cassette):
P-Glycoprotein (Pgp) - primarily transport parent molecules out of cells; MRP and related - transport Phase II conjugates of drugs and/or conjugated drug metabolites
Generic vs. Brand drugs
same active ingredient, identical dose; comparable kinetics - 10% of AUC and Tmax of brand name ones
Pharmacokinetics
what the patient does to the drug - Absorption, Distribution, Metabolism, and Excretion
Pharmacodynamics
What the drug does to the patient - intended, unintended, and socio-economic
Ibuprofen (e.g. Motrin; related Naproxen)
Pharmacologic class - NSAID
Therapeutic - analgesic, antipyretic, anti-inflammatory, anti-gout, anti-dysmennorhea
Pharmacodynamics - inhibition of prostaglandin synthesis via COX1 and COX2
pharmacokinetics - extensive metabolism in liver
avoid in pts. allergic to ASA
caution in renal failure, geriatric pts
drug interactions - warfarin, ASA, diuretics, antiHTN
OTC - 200-400mg po q4h prn
Dose -response
degree of response is a function of the amount of drug administered to the organism
Quantal Dose-Response Data
all or none effect; drug given to many animals at different doses and response is scored; information about the population; will have hyper-respondent and hyper-resistant individuals
Graded or continual dose-response
individual’s incremental response to increasing doses of drug
Drugs have 3 effects
1) primary effect - desired effect which is of therapeutic value
2) side effect or undesirable effect - not target effects, but not necessarily bad, and may be primary in other settings
3) toxic effects - bad!, loss of function, necrosis, organ failure, death
Important components of dose (5)
Amount, duration and frequency, chemical form, physical form, and route of exposure
Therapeutic Index
LD50/ED50 - should be greater than 1 and the bigger, the better; ideally want more than 10; based on population response, but importance is separatin of therapeutic benefit and toxic doses in individuals
Margin of Safety Index
LD1/ED99; more conservative; should be greater than 1 and bigger is better
Protective Index
ED50(desirable)/ED50(undesirable); should be greater than 1 and bigger is better