Pharmacology 9/2/05
Terms
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- Most drugs in solution are either _____ or ________, or ________ or _________
-
weak acids or weak bases,
nonionized, ionized - the ___form of drug is more lipid soluble
- nonionized
- The ______ at a site determines the degree of ionization
- pH
- HH Equation for an acid:
- pKa=pH + log [HA]/[A-]
- HH Equation for a base:
- pKa=pH + log i/n
- The degree of ionization is important where great changes in pH such as:
- stomach, and in urine
- What is ion-trapping?
- at equilibrium, the total drug (n+i) is greater where conditions favor ionization (weak acids)
- What are some well perfused organs?
- Brain, lungs, liver
- What are some poorly perfused organs?
- bone and adipose tissue
- What is the effect on glomerular filtration of protein binding?
- Less filtered-only free drug is filtered (not important if in kidney/liver)
- _____binds acidic drugs such as acetylcholine, barbiturates, penicillin, salicylates, sulfonamides, streptomycin, tetracyclines, warfarin
- Albumin
- _____ binds basic drugs such as Vit. B12, thyroxine, glucocorticoids
- a1-acid glycoprotein
- ____ fluctuates rapidly and varies among patients with age, stress, inflammation
- a1-acid glycoprotein
- Name three drugs that bind to the a1-acid glycoproteins:
- Vit B12, thyroxine, glucocorticoids
- 2 other glycoproteins:
- CBG, TBG coticosteroid and thyroxine binding globulin
- 2 major factors inhibit CNS drug distribution:
- BBB, CSF production carries it right out of cells
- Transplacental distribution affected by:
- lipid solubility, simple diffusion
- 3 other drug distribution barriers:
- prostate, testicles, eye globe
- Area of trapezoid:
- time*(h1+h2)/2
-
What is bioavailability?
F - fraction of drug that enters systemic circulation
- Formula for Amount of drug reaching systemic circulation:
- A= F*S*Dose
- Equation for equivalent dose:
- Dose of new=Amount absorbed old/S*F of new form
- Volume of distribution formula:
- Vd=(dose*F*S)/drug concentration initially achieved
- Loading dose equation:
- Loading Dose= [Vd*patients weight in kg*Cpdesired]/S*F
- Loading dose if want to ramp up loading dose:
- Ld=[Vd*pts weight kg*(Cpdesired-Cpinitial)]/S*F*