In these instances the drug is usually administered intravenously in a dose adjusted to keep the patient in a semi-conscious state in which inhibitions are reduced and various suppressed and emotionally charged material may be released. This procedure is essentially that used in the so-called 'truth serum' application in criminal investigations. Administration, Absorption, Distribution and Physiological Fate 49. In crystalline form, barbiturates are odourless, white or yellow powders, with a slightly bitter taste. Barbiturates are usually administered orally for both medical and non-medical purposes and are readily and efficiently absorbed by the stomach, small intestine, and rectum.
Absorption is more rapid on an empty stomach than if the drug is taken immediately after eating.
Both intramuscular and intravenous injections are also effective, but they are more prone to physiological complication and are generally avoided except for special purposes. After absorption into the bloodstream, barbiturates are initially distributed rather uniformly throughout the body, with the latency of the psychological response being partly a function of the facility of the particular drug in entering the brain. The body eliminates barbiturate activity in several ways. Most barbiturates are broken down or metabolized in the liver into relatively inactive substances which are excreted by the kidney in the urine, along with various quantities of the unaltered drug. The preceding factors of metabolism, excretion, and distribution are largely responsible for the differences in potency and duration of action among the different barbiturates.