If rate of elimination is directly proportion to plasma concentration the order of kinetics is –
Correct Answer: First
Description: Ans. is 'c' i.e., First o The rate at which elimination take place is subjected to important influences that are referred to as order of kineticso There are two orders of such elimination.1. First order kinetic (Linear kinetics)2. Second order kinetic (Non-linear kinetics)o Order of kinetic depends on the following formula.Rate of elimination a (Plasma concentration)ordero So, in zero order kineticRate of elimination a (Plasma Cone)0, i.e. 1.# That means rate of elimination is constant. Constant amount of drug is eliminated per unit time. Elimination is independent of plasma concentration.# As plasma cone, increases clearance decrease because elimination is constant (CL = Rate of elimination / Plasma Cone.).# Half life increase - As the concentration increases, clearance decreases so time required to reduce the plasma concentration to half will increase.o In first order kineticRate of elimination a (Plasma Cone)# That means rate of elimination is proportional to plasma concentration. Constant fraction of drug is eliminated per unit time.# Clearance remains constant because, as the plasma concentration increases, rate of elimination increases proportionately (CL = rate of elimination / Plasma Cone).# Half life remains constant because time required to reduce the plasma concentration to half, is same (rate of elimination changes proportionately with plasma concentration).o The drugs whose kinetics changes from first order to zero order at therapeutic concentration are said to follow pseudo - zero order kinetics or mixed order kinetics or saturation kinetics.o Drugs showing zero/pseudo-zero order kinetics:# Phenytoin# Tolbutamide# Theophylline# Warfarin# Alcohol# Salicylates (Aspirin)
Category:
Pharmacology
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