A semilog graph paper is a graph paper in which the x-axis is a normal linear scale, but the y-axis is a logarithmic scale. Semilog graph paper allows plotting the data at logarithmic intervals Without the need for logarithmic transformation.
The y-axis is divided into cycles, each represents 10-fold increase in values (a single log10 unit).
The first-order elimination rate constant is the rate constant for the elimination of the drug from the body. The elimination rate constant and the half life are dependent on the total body clearance and the volume of distribution of the drug.
CLT
Vd = k =0.693
t 1/2This rate constant represents drug elimination through all routes of drug elimination such as metabolism, renal excretion, and other routes.
The first-order elimination rate constant has units of time-1.
The half life is the time required for the amount of the drug or the plasma concentration of the drug to decrease by 50%. The half life has units of time.
The half life and the first order elimination rate constant are dependent on the total body clearance and the volume of distribution.
CLT
Vd = k =0.693
t 1/2The half life of a drug is constant within a patient (dose and concentration independent) when the drug elimination process follows first-order kinetics. However different patients may have different half lives for the same drug.
The half life is a very important parameter, because it indicates how fast the drug is eliminated from the body. Drugs with shorter half lives are eliminated faster than those with longer half lives.