cal formula Flashcards
Vd
Vd=dose/co
Vd = Volume of distribution
Co = Conc. of drug in plasma at zero time
loading dose
Loading dose = Vd x Css
Loading dose = Vd [C2 – C1]
- Loading dose .. is the dose needed to reach steady state
- Css = Concentration of the drug in blood at steady state
- C1 = Concentration of the drug in plasma
- C2 = Concentration of the drug needed to add to C1 to reach equired conc.
At steady state rate of drug input ? rate of elimination
At steady state rate of drug input=rate of elimination
Time required to reach steady state (Tss) =
4.5 or 5 t1/2
the time required for the concentration of a substance in the
body to decrease by half.
half life (T1/2)
Therapeutic index (TI)
Therapeutic index (TI) =LD50/ED50
- LD50 = Median Lethal Dose is the amount of an agent that is sufficient to kill
50 percent of a population of animals
- ED50 = Median Effective Dose is the dose that produces a quantal effect in
50% of the population
- Drugs with narrow TI = highly dangerous
bioavailability
Bioavailability =AUC/conc
Bioavailability = AUC ((oral)) /AUC ((iv)) x 100
Bioavailability =plasma conc of drug by any route/plasma conc of drug by iv
AUC = Area Under Curve
Specific gravity
Specific gravity = Wt. of substance ((Kg)) / Wt. of equal amount of water ((L))
Specific gravity = mass unit volume of sub. / mass unit volume of water
Specific gravity = Denisty of sub. / Denisty of equal amount of water
Denisty = Mass ((gm)) / Volume ((ml)) .. or Kg/L
density
Mass ((gm)) / Volume ((ml)) .. or Kg/L
mEq
mEq = Wt. ((mg)) x valency / M.wt
mEq = milliequivalent
clearance
Clearance (Cls) = 0.693 x Vd / T 1/2
Vd=dose/co
Cls=rate of elimination/drug conc
Cls =renal cls +non renal cls
Cls = Ke x Vd ………. Ke = elimination rate conistant
Creatinine clearance for male =(140 – age)x weight /72 x ser.
Creatinine
Creatinine clearance for male =
(140 – age)x weight /72 x ser.
Creatinine
Cr.cls for female
[(140 – age)x weight /72 x ser.
Creatinine]
molality
Molality ((m)) = No. of moles of solute / Kg mass of solvent
No. of moles = Wt. of solute / M.wt
Mass ((M)) = Denisty ((D)) x Volume ((V))
Molarity ((M))
Molarity ((M)) = No. of moles of solute / L volume of solution
osmolarity
Millimoles = [ wt. of sub. ((gm)) / M.wt ] x 1000
mosm = millimoles x no. of species
Examples Of no. of species:
Ex1: NaCl = 1 Na + 1 Cl = 2 ——– Ex2: CaCl2 = 1 Ca + 2 Cl = 3
— check problems No. 11 & 12
1kg= lb
2.2 pound ((lb))
1 grain = ? gm
0.065gm
1 teaspoonful ((tsp)) =? ml
5ml
1 tablespoonfull ((tbsp)) =? ml
15 mL
