The primary differences among many of these products are how fast they produce an effect and how long those effects last. Barbiturates are classified as ultrashort, short, intermediate and long-acting. The ultrashort-acting barbiturates produce anesthesia within about one minute after intravenous administration. After oral administration, the onset of action is from 15 to 40 minutes and the effects last up to 6 hours. These drugs are primarily used for sedation or to induce sleep.
Veterinarians use pentobarbital for anesthesia and euthanasia.
Effects of these drugs are realized in about one hour and last for about 12 hours, and are used primarily for daytime sedation and the treatment of seizure disorders or mild anxiety.