Pharmacology principles and equations Flashcards Preview

Boards > Pharmacology principles and equations > Flashcards

Flashcards in Pharmacology principles and equations Deck (15):
1

Equation for volume of distribution

Vd = amount of drug given IV / concentration in plasma

2

Equation for clearance

Cl = rate of elimination / plasma concentration
Cl = 0.7 x Vd / t1/2
Cl = K x Vd
*K = elimination constant, 0.7 / t1/2

3

Equation for Loading Dose

LD = Css x Vd
*Css = concentration desired at steady state

4

Equation for Maintenance Dose

MD = Css x Cl
*concentration at steady state x clearance

5

Effects of competitive inhibitors

increase Km, no change of Vmax
can be overcome by increasing substrate
decrease potency of the drug

6

Effects of noncompetitive inhibitors

decrease Vmax, no change of Km
cannot be overcome by increasing substrate
decrease efficacy of the drug

7

# of half-lives and percent of desired plasma concentration of drug

1 - 50%
2 - 75%
3 - 87.5%
4 - 94%

8

Inducers of Cyp450

Guinness, Coronas, and PBRs Induce Chronic Alcoholism

Griseofulvin, Carbamazepine, Phenytoin, Barbituates, Rifampin, St. John's wort, Chronic Alcoholism

9

Inhibitors of Cyp450

CRACK AMIGOS

Ciprofloxacin, Ritonavir (all protease inhibitors), amiodarone, cimetidine, ketoconazole, acute alcohol, macrolides (erythromycin, clarithromycin), isoniazid, grapefruit juice, omemprazole, sulfonamides

10

Renal clearance of a substance

Urine concentration x urine flow rate / plasma concentration

11

Renal plasma flow

Urine PAH x urine flow rate / plasma PAH

12

Renal blood flow

RPF / (1 - Hct)

13

Filtration fraction

GFR / RPF

-normal is around 20%

14

Filtered load

GFP x plasma concentration

15

Excretion rate

urine flow rate x urine concentration