TBL 4 - Pharmacokinetics Flashcards
What treatment should be given for an overdose of a weak acid (aspirin, phenobarbitone) and what is the effect?
NaHCo3 alkalinizes the urine.
What treatment should be given for an overdose of a weak base (amphetamine) and what is the effect?
NH4Cl acidifies the urine.
Where are weak acids absorbed?
Stomach
Where are weak bases absorbed?
Intestines
What is the equation for volume of distribution (Vd)?
Vd = Dose/Concentration
What does a high Vd mean?
Drugs with a high Vd will bind tightly in tissues and will have a higher concentration in tissues compared to the vascular compartment.
What does a low Vd mean?
Drugs with a low Vd will be retained within the vascular compartment.
What is the volume of the different compartments of the body (plasma, EC fluid, and IC fluid)?
Plasma: 4L
EC fluid: 14L
IC fluid: 28L
Total: 42L
What is P-glycoprotein and what does it do?
Is an efflux pump that opposes the distribution of drugs to tissues, leading to drug resistance.
What is the equation for loading dose?
LD = (Volume of Distribution)(Steady state Concentration)/Bioavailability
LD= (Vd)(Css)/F
What is included in Phase I of Metabolism of Drugs?
Oxidation, Reduction, and Hydrolysis
What are some examples of CYP450 Inducers?
Carbamazepine, Phenobarbitone, Phenytoin, Primidone, Rifampin, Chronic Alc, Glucocorticoids, St. John’s Wort, Nevirapine, and Griseofulvin
What are some examples of CYP450 Inhibitors?
Macrolides, Doxycycline, Sulfonamides, Cimetidine, Disulfiram, Grapefruit Juice, Itraconazole and Ketoconazole, Ritonavir, Ciproflaxcin, Amiodarone, Sulfonamide, Omeprazole, and Valproate.
What is included in Phase II of Metabolism of Drugs?
Conjugation with acetate, glucuronate, sulfate, or glycine.
Occurs in the cytosol
What is the equation for clearance?
CL=volume of distribution/k
CL=Vd/k
k = 0.7/t1/2
What is the equation for maintenance dose?
MD = (Clearance)(Steady state Concentration)(time interval)/bioavailability
MD = (CL)(Css)(t)/F
What is the equation for infusion rate?
Ko = (Steady state concentration)(clearance)
Ko = (Css)(CL)
What is the equation for the half life of a drug?
t1/2 = (0.7)(volume of distribution)/clearance
t1/2 = (0.7)(Vd)/(CL)
What is the equation for loading dose?
LD=(volume of distribution)(concentration in plasma)/bioavailability
LD=(Vd)(Cp)/F
Describe first order elimination.
The rate of drug elimination is proportional to plasma drug concentration at any given time.
A constant fraction of drug is eliminated per time.
Describe zero order elimination.
Constant or fixed amount of drug is eliminated per time, regardless of concentration.
Saturable.
Role of elimination is not affected by the serum concentration of the drug.
Ex: phenytoin, ethanol, aspirin
