BPT Clinical Pharmacology Flashcards
How is clearance calculated?
Clearance = dose / AUC
How is bioavailability calculated?
F = AUC(PO) / AUC(IV)
How is half-life (T1/2) calculated?
T1/2 = (0.693 x Vd) / Cl Vd = volume of distribution Cl = clearance
How is volume of distribution calculated?
Vd (L) = Ab (mg) / Cp (mg/L)
Ab = amount of drug in body
Cp = plasma concentration
How is the loading dose calculated?
LD = Vd * desired Cp
LD (oral drug) = (Vd * Cp) / F
Vd = volume of distribution
Cp = blood or plasma concentration
F = bioavailability
How is the maintenance dose calculated?
MD = Cp ss * Cl MD (oral drug) = (Cp ss * Cl) / F Cp ss = plasma concentration at steady state Cl = clearance F = bioavailability
Examples are inducers
CRAP GPS and St. John’s wort induce rage in me
AEDs
Carbamazepine Rifampin Alcohol (acute) Phenytoin Gruselvin Phenobarbital Sulfonylurea St. John's wort
Examples of inhibitors
SICK FACES.COM
Antibiotics and anti fungals
Sodium valproate Isoniazid Cimetidine Ketonazole Flucoonazole Alcohol chronic Chloramphenicol Erythromycin Sulfonamide Ciprofloxacin Omeprazole Metronidazole
Most drugs increase warfarin, what
A) reduces it
B) has no interaction?
Reduces warfarin CCRiSt Carbamazepine Cholestyramine Rifampicin St. John's wort
No interaction
Benzodiazepines
ACE/ARB
Statin
What are first order kinetics
Same proportion of drug eliminated per unit time
Most drugs
Pharmacokinetics in elderly and pregnant women
(clearance, Vd, protein binding)
Elderly
- reduced clearance
- reduced Vd (body mass, water reduced)
- less PB due to less albumin
Pregnancy
- increased clearance from increased CO/ blood flow through liver and kidney/enzyme induction
- increased Vd
- low PB hence lower measured drug but free levels unchanged
Paracetamol toxicity
Normally converted to non toxic metabolites by dilate and glucuronide
When this saturates, more paracetamol is converted via CYP450 into NAPQI, which is toxic
Plasma concentration at steady state calculation
Cpss = (bioavailability * dose) / dosing interval
