converted Flashcards
(500 cards)
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