General Pharm Flashcards
Km
1/2 V max
x intercept in lineweaver burke plot
effected by competitive antagonists
potency
Vmax
Y intercept on lineweaver burke plot
Efficacy
Effected by noncompetetive antagonists
Vd
Ammount of drug in system/Plasma drug concentration
Low Vd
- Large Charged substances that are confined to the blood
- May be protein bound
Medium Vd
- Generally accumulates in ECF
- Small charge substances
High Vd
-Lipophilic substances that accumulate in tissues or are very highly protein bound.
Half Life Calculation using Vd
t1/2 = vd*.7/clearance
-ln(2)=.7
Clearance
Cl = Elimination rate/plasma concentraion Cl = Vd*Ke (where Ke is elimination constant)
Loading Dose
Ld=Cp*Vd/F
Cp is desired plasma concentration, Vd is volume of distribution, and F is correction for bioavailability
Maintenance Dose
=Cp*Cl/F
Replace what is being cleared(Cp*Cl) and correct for bioavailability (F)
Number of half lives to achieve steady state
4 1/2
To calculate time, multiply half life times 4 1/2
Urine Elimination of Phenobarbitol, Aspirin, Methotrexate, TCAs
-Give NaHCO3 to alkalanize urine and trap weak acids in urine
Urine Elimination of Amphetamines
-Give NH3Cl to acidify the urine and trap weak bases in urine
Phase I elimination and population at risk
- Cyp 450’s
- Geriatric patients may lose this
Phase 2 Elimination and population at risk
- Glucuronidation, acetylation, sulfation
- Genetically slow acetylators will show increased half lives of drugs in this class
