Pentobarbital; Uses, Dosage, Side Effects, Drug Interactions

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Pentobarbital or pentobarbitone is a short-acting barbiturate. Pentobarbital can occur as both a free acid and as salts of elements such as sodium and calcium. The free acid is only slightly soluble in water and ethanol. It is a short-acting barbiturate that is effective as a sedative and hypnotic (but not as an anti-anxiety) agent and is usually given orally. It is prescribed more frequently for sleep induction than for sedation but, like similar agents, may lose its effectiveness by the second week of continued administration. In high doses, pentobarbital causes death by respiratory arrest. In the United States, the drug has been used for executions of convicted criminals. Lundbeck (one of many manufacturers) does not permit its sale to prisons or corrections departments to carry out the death penalty

Mechanism of Action of Pentobarbital

Barbiturates are metabolized primarily by the hepatic microsomal enzyme system, and the metabolic products are excreted in the urine, and less commonly, in the feces. Pentobarbital binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged. All of these effects are associated with marked decreases in GABA-sensitive neuronal calcium conductance (gCa). The net result of barbiturate action is acute? potentiation of inhibitory GABAergic tone. Barbiturates also act through potent (if less well characterized) and direct inhibition of excitatory AMPA-type glutamate receptors, resulting in a profound suppression of glutamatergic neurotransmission.

Indications of Pentobarbital

• Typical applications for pentobarbital are sedative, hypnotic for short term, preanesthetic and control of convulsions in emergencies
• Status Epilepticus
• Sedation
• Insomnia
• Sleeplessness
• Severe Convulsion
• Withdrawal Symptoms
• Generalized seizure
• Partial onset seizure Epilepsy
• Pentobarbital also has an application in reducing intracranial pressure in Reye’s syndrome, traumatic brain injury and induction of coma in cerebral ischemia? patients.
• For the short-term treatment of insomnia.

Contra-Indications of Pentobarbital

• Porphyria
• High blood pressure
• Heart hisease
• Abnormally low blood pressure
• Pneumonia
• Lung failure causing loss of breath
• Decreased lung function
• Liver problems
• Periods of Not breathing
• Pregnancy
• Chronic obstructive lung disease

Dosage? of Pentobarbital

Strengths: 30mg ;60 mg; 50 mg;100 mg; 120 mg; 200 mg; 50 mg/mL;  18.2 mg/5 mL

Insomnia

• Oral capsules or elixir: 100 mg orally at bedtime.
• Rectal suppository: 120 to 200 mg rectally.
• Injection: 100 to 200 mg IM or IV.

Sedation

• Oral capsules or elixir: 100 mg orally at bedtime.
• Rectal suppository: 120 to 200 mg rectally.
• Injection: 100 to 200 mg IM or IV.

Side Effects of Pentobarbital

The most common

• Memory or concentration problems
• Excitement, irritability, aggression, or confusion
• Dizziness
• constipation
• muscle aches
• Nausea and vomiting
• Severe stomach ache
• diarrhoea,
• anorexia,
• flatulence,
• headache,
• dizziness,
• heartburn
• joint pain

 Common

• Memory loss.
• Impaired attention span.
• Agitation.
• Depression.
• Nausea and vomiting
• Severe stomach ache
• Severe diarrhea
• Mouth sores
• Vaginal thrush
• Skin rash
• Headache

Rare/Less common

• Confusion
• Fever or sore throat
• Rash
• Slowed breathing or breathing difficulties
• Sores in the mouth
• Broken blood vessels under the skin
• Easy bruising or bleeding
• Swelling of the eyes, lips, or cheeks
• Blistering or peeling of the skin
• Restless muscle movements in the eyes, tongue, jaw, or neck

Drug Interactions of Pentobarbital

Pentobarbital may interact with following drugs, supplements & may change the efficacy of the drug

• albendazole
• alcohol
• allopurinol
• alpha blockers (e.g., alfuzosin, doxazosin, silodosin, tamsulosin)
• amphetamines (e.g., dextroamphetamine, lisdexamphetamine)
• anti-cancer medications (e.g., cabazitaxel, docetaxel; doxorubicin; etoposide, ifosfamide, irinotecan, vincristine)
• antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• “azole” antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• baclofen
• barbiturates (e.g., butalbital, pentobarbital phenobarbital)
• benzodiazepines (e.g., chlordiazepoxide, clonazepam, diazepam, lorazepam)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
• bupropion
• calcitriol
• calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
• carbamazepine
• carvedilol
• celecoxib
• ciprofloxacin
• clobazam
• oral corticosteroids (e.g., dexamethasone, hydrocortisone, prednisone)
• cyclosporine
• doxycycline
• folic acid
• gabapentin
• “gliptin” diabetes medications (e.g., linagliptin, saxagliptin, sitagliptin)
• lansoprazole
• loperamide
• losartan
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• methylfolate
• methylphenidate
• multivitamins
• montelukast
• nitrates (e.g., isosorbide dinitrate, isosorbide mononitrate)
• ondansetron
• phenytoin
• progestins (e.g., dienogest, levonorgestrel, medroxyprogesterone, norethindrone)
• proton pump inhibitors (e.g., lansoprazole, omeprazole)
• ranitidine
• selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine,paroxetine, sertraline)
• sildenafil
• “statin” anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
• theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
• thiazide diuretics (e.g., chlorothiazide, hydrochlorothiazide)
• tramadol
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
• valproic acid
• warfarin
• zafirlukast

Pregnancy & Lactation

FDA Pregnancy Category D

Pregnancy

Medications used to prevent major seizures should not be stopped. The use of this medication is not recommended during pregnancy. However, the decision about whether or not to stop the medication must weigh the potential benefits against the potential risks. If you become pregnant while taking this medication, contact your doctor immediately.

Lactation

This medication passes into breast milk. If you are a breastfeeding mother and are taking phenobarbital, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding.

References