Question

Question

To prepare a 15 kg dog for surgery,150 mg of anesthetic phenobarbitol is administered intravenously. The reaction in which the anesthetic is metabolized is first order in phenobarbitol and has a half-life of 4,5 h. After about 2 hours,the drug begins to lose its effect.However,the surgical procedure requires more time than had been anticipated.What mass of phenobarbitol must be re-injected to restore the original level of anesthetic in the dog? (answer: 40 mg )