Pharmacology Flashcards
What is the MOA of Dopamine?
- Has direct alpha, beta, and dopaminergic effects
- Effects likely to be dose related;
- Dopaminergic vasodilatory effects at low dosages
- Beta effects at mid-range dosages
- Alpha effects at high dosages
- Dopamine generally causes a moderate vasoconstriction and increase in BP with little change/modest increase in cardiac output
What is the MOA of Dobutamine?
- Synthetic analogue of dopamine
- Strong beta-1 agonist activity
- Mild beta-2 and alpha-1 receptor activity
- NO dopaminergic effects
- Generally causes moderate vasodilation and a marked increase in cardiac output with little change in blood pressure
What is the MOA of ephedrine?
- Acts by increasing the release of norepinephrine from sympathetic nerve endings
- Has MILD direct beta agonist effects
- Modest decrease in heart rate, increase in cardiac output, vascular resistance and arterial blood pressure
- Prolonged use can deplete norepinephrine stores, resulting in tachyphylaxis
What is the MOA of norepinephrine?
- Primarily an alpha-receptor agonist
- Minimal beta-1 receptor activity
- Generally causes vasoconstriction and increases BP with variable effects on HR.
- CO may increase, decrease, or remain unchanged
- Animals with an effective circulating volume but with vasodilation would likely have an increase in CO dt venoconstriction of capacitance vessels
- CO may increase, decrease, or remain unchanged
What is the MOA of phenylephrine?
- Strict alpha receptor agonist
- NO beta activity
- Causes vasoconstriction and an increase in arterial BP, decrease in HR
What is the MOA of vasopressin (with regards to vascular actions…)?
- Acts via vasopressin V1 receptor increasing intracellular calcium and vasomotor tone
- PURE vasoconstritor with no diret effect on heart
- Increase in systemic vascular resistance
- Baroreceptor reflex decrease in HR
No change in contractility - No change or a decrease in CO
- Baroreceptor reflex decrease in HR
What is the MOA of epinephrine?
- Potent beta-1, 2 and alpha-1,2 receptor agonist
- Positive inotrope, chronotrope, arteriolar and venular vasoconstrictor
- Can be used in critically ill patients, but therapeutic margin may be much lower due to higher incidences of sinus tachycardia, ventricular arrythmias and increased lactate levels
What is the MOA of isoproterenol?
- Potent beta agonist with NO alpha action
- Potent vasodilator and hypotensive agent
- Increases heart rate and cardiac output, decreases blood pressure
- If administered very carefully while BP is monitored and maintained, can provide potent augmentation of forward blood flow and tissue perfusion
Define breakpoint.
The highest achievable MIC that still inhibits growth of the micro-organism.
Based on achievable serum concentrations, not tissue, which are typically slightly less than serum.
Define MIC
The lowest concentration of an antimicrobial that inhibits growth of a micro-organism.
An organism is susceptible to the antimicrobial if the MIC is below the breakpoint for that antimicrobial.
What are the 3 types of bacterial resistance?
- Intrinsic resistance
- Inherent feature of a microorgnaism that results in lack of activity of an antimicrobial drug or class of drugs.
- Circumstantial resistance
- When an in vitro test predicts susceptibility, but in vivo, the antimicrobial lacks clinical efficacy
- May be due to lack of the drug to penetrate the site of infection or inability to work because of a local pH
- When an in vitro test predicts susceptibility, but in vivo, the antimicrobial lacks clinical efficacy
- Acquired resistance
- Change in the phenotypic characteristics of a micro-organism (compared to wild type) which confers decreased efficacy of an antimicrobial against that microorganism (MULTIPLE mechanisms!)
What defines an MDR infection?
Organisms that are not susceptible to at least one agent in three or more classes of drugs to which they are usually susceptible
What are the 3 primary mechanisms of acquired resistance?
- A decrease in intracellular drug entery from efflux pumps or altered membrane structure
- Enzymes that modify or destroy antimicrobials
- Modification of the target of the antimicrobials (DNA gyrase mutation)
Genes imparting resistance are shared among organisms by integrins, plasmids and transposons that facilitate rapid transfer of multidrug resistance.
What is a beta-lactamase?
An enzyme that hydrolyzes and disrupts the beta-lactam ring in the beta-lactam group of antimicrobials. This confers resistance to many penicillins.
Discuss escalation versus de-escalation protocols.
- Escalation
- Protocols that involve a single antibiotic, carefully chosen to treat what is thought to be the most likely source of infection
- After C&S results return, either to be continued or changed if it is wrong
- De-escalation
- Protocols that involve broad-spectrum antibiosis with the intent to rapidly narrow the spectrum to the most appropriate antibiotic (possibly only a single antibiotic) as soon as culture results return
