Capstone - Ex 1 Flashcards
Pharmacodynamics
Mech of action
Pharmacokinetics
Distribution and metabolism
Potency vs Efficacy
Potency: amount of the drug req’d to produce a desired effect
Efficacy: measure of maximal effect
Dissociation constant (Kd)
LOW Kd means a HIGH affinity –> more potent
HIGH Kd means a LOW affinity –> less potent
Which is more important? Efficacy or potency
Efficacy!
A less potent drug with high efficacy will produce better results than a less efficacious drug with high potency
Which is more potent and efficacious… morphine vs buprenorphine
Buprenorphine is more potent, but less efficacious (partial agonist)
Morphine is less potent, but more efficacious (full agonist)
Agonists vs Antagonists
Agonists have an effect
Antagonists bind tot he receptor but have no effect (block effect of the agonist)
Competitive vs Non-competitive Antagonists
Competitive: compete with agonists for the active site (shift DR curve to the right)
Noncompetitive: binds to active or allosteric site; decreases the maximal response of the agonist (shifts DR curve to the right and DOWN)
Therapeutic Window
Range of doses that produce therapeutic response w/out causing any significant adverse effect in patients
Therapeutic index
TI is a comparison of the amount of a drug that causes the therapeutic effect to the amount that causes toxicity
High TI - good!
Low TI - bad! only req small increase in dose to produce toxic effects
Which drugs are best absorbed from stomach?
Lipid soluble drugs (alcohol!)
Weak acids (uncharged - aspirin)
Effects of pH on drug absorption
Weak acids are absorbed from acidic environments (stomach, acidic urine)
Weak bases are absorbed from basic environments (small intestine, basic urine)
1st Pass Effect
Drugs given orally are absorbed by the stomach & intestines –> portal circulation passes through the liver where these drugs may be metabolized and/or secreted before reaching systemic circulation
Bioavailability
Fraction of drug that is absorbed and escapes first-pass elimination - drug that is able to have an active effect
Central vs Peripheral Compartments
Central: well-perfused organs/tissue
Peripheral: poorly perfused (skin, mm, fat)
What are the two main routes of drug elimination?
Metabolism - Liver
- Phase 1 (oxidation by cytochrome p450s)
- Phase 3 (conjugation)
Excretion - kidney & liver
- Kidney –> urine
- filtration: glomerulus
- secretion: proximal tubules, transporters
- Liver –> bile
- transporters
- may be reabsorbed from the gut
What is drug clearance?
Volume of blood cleared by an organ per unit time
Steady state for CRI (IV(
Increases in dosing rate lead to proportional increase in steady state plasma concentration
Steady state for repeated doses
Approaches steady state after 4 half lives, but with fluctuations
- reached after about 4 half lives
- proportional to dosage and inversely proportional to dose interval
Concentration-dependent Abx
Brief periods of high drug levels are preferred
Time-dependent Abx
Long periods above a minimum level are preferred
What is a loading dose?
Dose you give at start of treatment to quickly reach a steady-state concentrations
What is ‘minimum inhibitory concentration (MIC)’ in regards to Abx?
MIC is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation
Receptor vs Non-receptor mediated Toxicity
Receptor-mediated: “overstimulation” of ‘normal’ receptors
Non-receptor mediated:
bind to many proteins, DNA
How much liver damage is needed to overwhelm the liver’s metabolism of drugs?
> 80%
No routine test available to test liver metabolism of drugs
What is the chemical restraint used for fish?
Tricaine methanesulfonate (MS-222)
Local anesthetic that blocks VG Na channels in both PNS and CNS
Chemical restraints for amphibians?
Topical gel applied to skin
In many birds and some reptiles, the ____ jugular v is larger than the other and is used preferentially
RIGHT
What common anti-parasitic drug can kill Chelonians?
Ivermectin!
