converted Flashcards Preview

Pharmacology > converted > Flashcards

Flashcards in converted Deck (500)
Loading flashcards...

What is pharmacokinetics?

Deals with what the body does to the drug: absorption, distribution, sites of action, tissue storage, metabolism and excretion.


What factors are involved in drug permeation/absorption?

Solubility, concentration gradient, surface area, vascularity, ionization.


In what form can drugs cross cell membranes?

Non-ionized form (lipid soluble).


In what form are drugs excreted?

Ionized form (water soluble) are better renally excreted


What factors affect renal clearance of drugs?

The drug must be in free form, ionized or nonionized. Only nonionized drug can be actively secreted or reabsorbed.


What effect does acidification of urine have on drugs?

Increases ionized fraction of weak bases and increases their renal elimination. NH4Cl, vitamin C, cranberry juice.


What effect does alkalinization of urine have on drugs?

Increases ionized fraction of weak acids and increases their renal elimination. NaHCO3, acetazolamide.


Urine alkalinization agents

NaHCO3, acetazolamide


Urine acidification agents

NH4Cl, vitamin C, cranberry juice


What is Cmax?

Maximal drug level obtained with the dose


What is Tmax?

Time at which Cmax occurs


What is the lag time?

Time from administration to appearance in blood


What is onset of activity?

Time from administration to blood level reaching minimal effective concentraion


What is duration of action?

Time that the plasma concentration remains above minimial effective concentration


What is time to peak?

Time from administration to Cmax.


What is bioavailability?

Is the fraction of a dose that reaches the systemic circulation after 1st pass metabolism


What is the first-pass effect?

Is the decrease in bioavailability of an oral drug after passing through intestines or from the portal blood through the liver. Portal blood will always have a higher concentration of the drug before passing for the first time through the liver.


What is bioequivalence and what factors are involved?

Bioequivalence is the similarity between two formulations of the same drug. To be bioequivalent they must have the same bioavailability and the same rate of absorption.


How are rate of absorption, Tmax and Cmax related?

The faster the rate of absorption the smaller Tmax and larger Cmax. Tmax and Cmax are rate dependant.


What is distribution?

Is the process by which a drug reaches the target tissues from systemic circulation.


What factors affect distribution of a drug?

Protein-binding capacity and competition between drugs for protein-binding sites, barriers such as placenta or brain.


What is volume of distribution?

Correlates dose given with the plasma level at time X. Vd=Dose/C0. C0=[plasma] at zero time.


What is the significance of the volume of distribution?

It's needed to calculate a loading dose; when Vd is low, a high fraction of the drug is bound to proteins; when Vd is high, a big fraction of the drug is being sequestered in tissues.


Relationship between plasma concentration and volume of distribution

Inversely proportional. The higher the plasma concetration, the lower the volume of distribution


Relationship between dose and plasma concentration

Directly proportional.


What is redistribution?

Is when a lipid-soluble drug gets temporarily stored in fat tissue before being eliminated.


What is the significance of the redistribution rate?

A second dose of a CNS drug redistributes to fat in lesser amount because fat is saturated" therefore allowing more drug to enter the CNS and increasing the duration of action."


What is biotransformation?

Is the conversion of a drug to a more water-soluble form to be excreted. A metabolite may or may not have pharmacologic action.


What is phase I biotransformation?

Modification of the drug via oxidation, reduction or hydrolysis.


What is microsomal metabolism?

Cytochrome P450 isoenzymes in the SER require NADPH for oxidation and reduction of drugs.