Percentage of thiopentone used for induction is

The usual concentration of thiopental is 2.5%. The usual doses of thiopental (3 to 4 mg/kg) and thiamylal (3 to 4 mg/kg) are approximately twice the dose of methohexital (1 to 2 mg/kg). In dose-response studies, the ED50 for thiopental ranged from 2.2 to 2.7 mg/kg, and the ED50 for methohexital was 1.1 mg/kg. Less interpatient variability is seen in the dose-response to barbiturates than to benzodiazepines when used for anesthesia induction, but significant variability remains in the dose of thiopental required to induce anesthesia. Interpatient dose variability is related to the presence of hemorrhagic shock, cardiac output, lean body mass, obesity, gender, and age. Hemorrhagic shock, lean body mass, age, and obesity explain the variability of patients' responses resulting from a decrease in the central volume of distribution. Finally, patients who have severe anemia, burns, malnutrition, widespread malignant disease, uremia, ulcerative colitis, or intestinal obstruction also require smaller induction doses of barbiturates. Ref: Miller's anesthesia 8th edition Ref: Morgan & Mikhail's clinical anesthesiology 6e