Pharmacology Flashcards
What is a graded dose response curve?
Looks at effect on individuals, looks at magnitude of response (plots intensity vs. dose)
What is a quantal dose response curve?
Looks at effect on populations, looking for absence or presence or particular phenomenon (plots population % vs. dose)
What is LD50?
lethal dose for 50% of the population
What is ED50?
effective dose for 50% of the population
What is TI (therapeutic index)?
LD50/ED50
What is margin of safety and what are its implications?
LD1/ED99 Larger number = safer drug
What is TLV?
threshold limit value (part of occupational toxicology)
What is TLV-TWA?
Time weighted average values, safety of compound a worker is exposed to over an 8 hr day over a 40 hr week (person can be exposed to compound at that limit as long as there is an equal amount of time below that limit)
What is TLV-C?
Ceiling value, concentrations you cannot exceed, even instantaneously
What is PEL?
permissible exposure limits, federal regulations, not changed unless the law is changed
What is bioaccumulation?
Increasing concentration of a persistent environmental chemical in the tissues of an organism as a result of the chemical physiochemical properties (part of environmental toxicology)
What is biomagnification?
Increasing concentration of chemical w/ each progressive link of food chain (part of environmental toxicology)
What are 4 ways a toxicological response can be modified?
- Potentiation or supra-additive effects
- Physical and chemical characteristics (eg. sensitivity to pH, stability, solid vs. liquid vs. gas forms)
- Routes of administration (IV, oral, skin, inhalation)
- Metabolism
How can pharmacokinetic drug interactions affect toxicity during absorption (3 ways + examples)?
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Direct interaction
- tetracyclines (antibiotic) precipitate sulfonamides (antibiotic) –> less sulfonamide will be available for absorption
- carbenicillin (antibiotic) reacts w/ aminoglycosides (gentamicin) to form amides –> inactivation of aminoglycosides
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GI absorption
- Altering tract function:
- laxatives increase motility –> decrease absorption - antibiotics decrease gut flora –> decrease vit K synthesis –> affects clotting –> increases response to oral anticoagulants
- Altering contents
- tetracyclines chelate Ca2+ (eg. Antacids) –> tetracycline is unabsorbable - H2 blockers increase pH/decrease acid secretion –> changes dissolution properties
- Resins (cholestyramine) binds vitamins and digoxin (fat soluble)
- Altering tract function:
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Dermatomucosal absorption
- DMSO solvent allows permeation of skin by drugs - Patches (fentanyl, nicotine) absorbed by potential oils in skin
How can pharmacokinetic drug interactions affect toxicity during distribution (2 ways + examples)?
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Plasma protein binding (acid drugs bind to albumin)
- Salicylates displace warfarin and phenytoin –> more free drug –> toxicity
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Displacement from tissue binding sites
- Quinidine (anti-arrhythmic) displaces digoxin –> available toxicity elsewhere
How can pharmacokinetic drug interactions affect toxicity during metabolism (2 ways + examples)?
- Induction- slowly induces/increases metabolism of a drug - Phenobarbital (anti-epileptic, tranquilizer) - Rifampin (antibiotic) - Pollutants (polycyclic aromatic hydrocarbons PAH) - Chronic ethanol 2. Inhibition- high enough concentration rapidly inhibits activity of drug, covalent binding can be irreversible - Chloramphenicol - Ketoconazole- inhibits CYP3A4, anti-fungal - Cimetidine (Tagamet)- inhibits propranolol and theophylline metabolism, beta-blocker
How can pharmacokinetic drug interactions affect toxicity during excretion (3 ways + examples)?
- Block transport mechanism: weak acids transport in proximal tubules - Probenicid blocks penicillin –> increases half life (blocks availability of transport mechanism of penicillin out of body, so keeps it in body longer) –> don’t have to dose as often 2. Alter pH of urine (through ion traffic) - Bicarb increases pH –> increases elimination of weak acids (important for OD of phenobarbital) - Ammonium chloride and ascorbic acid decrease pH –> increases elimination of weak bases 3. Diuretics - Cisplatin: decreases tubular concentration of toxic compounds –> decreases renal toxicity - Thiazides: decrease K+ (essential for normal cardiac function) –> toxicity w/ digoxin
What is potentiation?
A compound that has little/no activity yields an order of magnitude response when added to another compound
What is synergy?
2 drugs added together produce a greater response than expected
What are some examples of agonists and antagonists?
- Naloxone- antagonist to opiates - Tamoxifen: antagonist to estrogen positive receptors in breast tumors, but acts like estrogen (agonist) for bone - Cimetidine, Ranitidine- H2 blockers
How can pharmacodynamic drug interactions cause physiologic alterations?
- Hydralazine decreases peripheral resistance (decreases BP) –> causes reflex tachycardia (affects heart) –> give propranolol (beta-blocker) to decrease response on heart - Ethanol increases fluidity of plasma membrane –> increases Cl- influx (chloride channels) –> affects GABA (inhibitory NT)