Pentobarbital dosage

Respiratory and cardiovascular effects of maitotoxin have been studied in pentobarbital anaesthetized cats (21). Sublethal doses of maitotoxin induced an important hyperventilation phase, hypertension and a transitory tachycardia followed by slight bradycardia. Higher dosage caused respiratory depression, cardiac arrhythmias and tachycardia leading to cardiac failure. Artificial respiration did not modify the cardiac responses. 

Other barbiturates are manufactured as a powder that is injected into the patient s vein. In addition, pentobarbital is manufactured as a suppository that is inserted in the rectum. Pentobarbital is also available in capsule, tablet, elixir, and injection dosages. Phenobarbital is produced in capsule, tablet, injection, and elixir dosages. 

Pentobarbital form Dosage form Vehicle Particle size (pm) LD50 Potency ratio... 

Barbiturates Opiates Pentobarbital tolerance test initial detoxification at upper limit of tolerance test decrease dosage by 100 mg every 2-3 days Methadone 20-80 mg orally daily taper by 5-10 mg daily or clonidine 2 mcg/kg three times a day x 7 days taper over additional 3 days... 

In the solid (crystalline) form the barbituric acid exists in the triketo or lactam form. In aqueous solution tautomerism to the enolic lactim occurs the enolic hydroxyl (at C-2) is acidic acid and is ionized according to the particular drug s pKa (e.g., pentobarbital = 8.0, phenobarbital = 7.5). Titrating such a solution with a stoichiometric equivalent of base such as NaOH will convert the lactam quantitatively to the barbiturate s sodium salt, which can be isolated. Many barbiturates are commercially produced both in the lactam and in the sodium enolate salt form. Of course, the salts are water soluble and thus are used to formulate injectable dosage forms including those for IV anesthetic use. 

Figure 9.1 Pentobarbital concentrations in plasma after a single 200 mg dose in various dosage forms. Aqueous solution ( - ) aqueous suspension ( -- ) tablet, sodium salt (o-o) tablet, acid (o--o). (With permission from Sjorgen et al (1965.)...

Many barbiturates are cyclic amides of barbituric acid that act as sedatives in small dosages or sleep inducers in larger dosages. They are often habit forming. Barbiturate drugs include phenobarbital (Luminal) and pentobarbital (Nembutal). 

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