Pharma General Principles Flashcards
(37 cards)
permeation depends on
- solubility (ionized are water soluble, unionized are lipid soluble)
- conc gradient (only FREE and UNionized contribute)
- SA and vascularity
some weak acid drugs
- aspirin (ASA, acetyl salisylic acid)
- penicillin
- cephalosporins
- loop & thiazide diuretics
some weak base drugs
- morphine
- local anesthetics
- amphetamines
- PCP (angel dust)
in which environment is a weak acid lipid soluble?
a weak acid is lipid soluble in an acidic environment (AH)
in which environment is a weak base lipid soluble?
a weak base is lipid soluble in a basic environment (B)
What forms of drug are filtered through the kidney?
- both ionized and nonionized forms filtered but the drug MUST be FREE and UNBOUND
- also note than ionized form is trapped in the filtrate b/c it’s NOT lipid soluble (whereas unionized can be reabsorbed or secreted b/c it is lipid soluble)
if overdose on weakly basic drug (ex: amphetamine, PCP), what should do?
- acidify the urine to incr renal elimination (in an acid environ, a weak base is ionized and therefore water soluble and lipid insoluble)
- can give vitamin C, cranberry juice, or the fav NH4Cl (ammonium chloride)
if overdose on weakly acidic drug (ex: aspirin), what should do?
alkalinize the urine (with NaHCO3 or acetazolamide) to incr renal elimin
NH4+ is
ammmonium
NH3 is
ammonia
fastest route of absorption
inhalation
bioavailability of IV admin drug
100%
bioavailability calculation
f = AUCpo/AUCiv (AUC = area under curve, f = bioavailability, po = per oral)
which a stronger barrier to distribution - placenta or blood-brain barrier?
BBB
BBB is only permeable to . . .
- lipid soluble drugs
* very low mw drugs (ex: Li+, EtOH)
what kinds of drugs are safer during pregnancy?
- water-soluble (b/c can’t cross membranes)
- large
- protein-bound
(ex: choose PTU over methimazole b/c PTU more highly protein-bound; Phenobarbital safer anticonvulsant b/c highly protein-bound)
volume distribution
Vd = Dose/Co (Co = plasma conc at time=0)
note L vs. L/kg . . . don’t forget to multiple by pt wt
interpreting low v high volume distribution
- low - lots of drug bound to plasma protein
* high - lots of drug sequestered in tissues
effect of P450 inducers v. inhibitors
- inducer –> incr P450 enzymes –> decr drug level in plasma (for certain drugs) therefore may need to give more drug
- inhibitor –> decr P450 enzymes –> less metab –> risk of drug toxicity b/c incr drug level in plasma
some classic P450 inducers?
- phenobarbital
- phenytoin
- carbamazepine
- rifampin
- chronic alcohol
some classic P450 inhibitors?
- cimetidine (OTC med)
- marcrolides (esp erythro-) . . .(note azythromycin is not a P450 inhibitor)
- ketonconazole
- “avirs” - antivirals, proteases for HIV
- ACUTE alcohol
- grapefruit juice
Phase I Rxns
hydrolysis, oxidation (monoamine oxidase, CYP450), alcohol metabolism, reduction
Phase II Rxns
- conjugation rxns (endogenous compound is conjugated to a drug by a transferase)
- includes glucuronidation, acetylation, GSH conjugation
zero order kinetics
constant AMOUNT eliminated per unit time
* thus t1/2 is variable
ex: zero “peas” for me: phenytoin, EtOH, aspirin
