A drug is given intravenously and drug concentrations in blood measured at 1 and 4 hour are 26 and `18mu g//mL`. What is the half-line of drug and at what time will the level decreases to `10mu g//mL`

Explanation

`t = (2.303)/(lambda) log (N_(0))/(N)`
`t = 1 hr, N = 26 mu g//mL`
`:. 1 = (2.303)/(lambda) log (N_(0))/(26)` ...(i)
`t = 4hr, N = 18 mug//mL`
`:. 4 = (2.303)/(lambda) log (N_(0))/(18)` ....(ii)
`:.` By eqn. (i) and (ii)
`lambda = 0.123 hr^(-1)` and `N_(0) = 29.40 mug//mL`
`:. t_(1//2) = (0.693)/(lambda) = (0.693)/(0.123) = 5.63 hr`
Now `t = (2.303)/(0.123) log (29.40)/(10) = 8.77 hr`