Pharmacology Workshop - Part 2

I didn't include any of his questions, please refer to Gabe's anki question deck for that, xoxo GossipGirl

Elimination

How much of a drug is removed from the body. The effect of the drug is reduced both by metabolism and by excretion (the LIVER metabolizes, the KIDNEY excretes)

breath, sweat, stool, urine

routes of elimination (most from the kidneys)

clearance

a measurement of the volume of plasma from which a substance is completely removed per unit time

glomerular filtration rate

insulin is a drug that is freely filtered, is not absorbed by the nephron, and is not secreted by the nephron. That means that is we were to measure insulin’s clearance, we would have a direct measurement of the filtration rate at the glomerulus, the……

clearance equation

clearance = filtered + excreted - absorbed

theoretical clearance

= %freely filtered x GFR

actual clearance

= Drug concentration/time

secreted

if actual clearance > theoretical clearance, the drug will be…

absorbed

if actual clearance < theoretical clearance, the drug will be…

elimination concentration

= 0.7/half life

CL

= Vd x K ~OR~ =(Vd x 0.7)/half life

half life

how much time it takes to remove half of the drug from the body. It is a value of time, can be calculated using a formula (=0.7/K)

Zero-order kinetics

Has a constant slope on a regular graph, and a concave curve on a log graph. Alcohol elimination follows this

First-order kinetics

Has a constant slope on a log graph, and convex curve on a regular graph. Most drugs follow this

Loading dose

an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose; 4-7 half-lives more time within the range faster

pharmacodynamics

term used to describe the effects of a drug on the body. These effects are typically described in quantitative terms

potency

The affinity of the drug to bind to receptor, the minimum amount of drug that binds to drug to elicit 50% of the maximum response. EC50

efficacy

The effect of the drug on the receptor, the amount of drug required to elicit the maximum response of 100%. Emax

Therapeutic index

TI = (TD50 or LD50)/ED50

ED50

median effective dose that produces therapeutic effect in 50% of a population

TD50

median toxic dose that produces toxic effect in 50% of a population

LD50

median lethal dose that produces lethal effect in 50% of a population

Summation

Two drugs with different mechanisms that elicit the same (and together, stronger) response

additive

Two drugs with the same mechanism that elicit the same (and together, stronger) response

synergism

One drug alters pharmacokinetic of the other drug to create a stronger response than just the sum of the parts

chemical antagonism

a phenomenon wherein two or more agents in combination have an overall effect that is less than the sum of their individual effects, A chemical antidote; ex. gastric acid and antacids, or heavy metal and a chelating agent, or heparin and protamine

physiological antagonism

non-competitive type of antagonism that occurs when a substance produces an effect that counteracts another substance's effect, without binding to the same receptor. The antagonist binds to a different receptor and produces an opposite physiological response. 

pharmacological antagonism

A drug that binds without activating its receptor and thereby prevents activation by an agonist

competitive antagonism

Both agonist and antagonist bind to the same site

reversible antagonism

a kind of competitive antagonism where adding agonist dose can reverse the effect

irreversible antagonism

a kind of competitive antagonism that occurs when the antagonist binds to the same spot on the receptor as the agonist but dissociates from the receptors very slowly or not. As a result, when the agonist is delivered, there is no change in the antagonist occupancy

non-competitive antagonism

interfere with agonist by either binding at an allosteric site or interfering at a downstream site to prevent expression

sequential block synergism

a situation where two or more drugs, each acting on a different step in the same metabolic pathway, combine to produce a significantly greater effect than the sum of their individual effects, essentially "blocking" the pathway more effectively by targeting consecutive steps in the sequence; this is considered a type of synergistic interaction where the combined effect is much stronger than either drug alone. 

alter pharmacokinetic synergism

This happens when one drug alters the way another drug is absorbed, distributed, or eliminated within the body, thereby enhancing its overall effect