Phenobarbital

Brand names

• Aasquel
• Alised
• Alubelap [CD]
• Aminodrox-Forte
• Antispasmodic [CD]
• Azpan
• Barbidonna [CD]
• Barbilixir
• Barbita
• Belap
• Belladenal
• Bellergal
• Bronchotabs[CD]
• Bronkolixir [CD]
• Cafergot-PB
• Chardonna-2 [CD]
• Daricon PB
• Diclophen [CD]
• Donna-Sed
• Donnatal [CD]
• Donphen
• Ergobel [CD]
• Eskabarb
• Eskaphen B [CD]
• Floramine
• Gardenal
• Hybephen [CD]
• Hypnaldyne [CD]
• Kinesed [CD]
• Luminal
• Neospect
• Neuro-Spasex [CD]
• Neuro-Trasentin [CD]
• Neuro-Trasentin Forte [CD]
• Novalene
• Phedral [CD]
• Phenaphen Capsules [CD]
• Phenaphen No.2, 3, 4 [CD]
• Phenergan w/Codeine [CD]
• Phyldrox
• Ouadrinal [CD]
• Relaxadron
• SBP [CD]
• Scodonnar [CD]
• Sedacord [CD]
• SK-Phenobarbital
• Solfoton
• Spasquid [CD]
• Spazcaps
• Thalfed [CD]
• Theocardone
• Theocord [CD]
• Theolixer
• Vitaphen

Usage

Primarily used for sedation before surgery and to control certain types of seizures. With the availability of newer sleep inducing medicaments, it is now rarely used for the short-term treatment of insomnia.

How it works

Barbiturates such as phenobarbital act as powerful sedatives by reducing activity in the central nervous system (the brain and spinal cord).

Side effects

Serious

Excitability, confusion, or excessive sedation to the point you cannot be awakened. Also yellow discoloration of eyes or skin; swollen eyelids, face, or lips; wheezing; or rash (may be signs of medicament allergy); sores on the lips or mouth. Seek medical help immediately.

Common

Clumsiness, unsteadiness, persistent drowsiness, dizziness or lightheadedness.

Less common

Anxiety or nervousness, nightmares, insomnia, constipation, feeling faint, irritability, headache, nausea or vomiting.

Possible interactions

Other medicaments:

Phenobarbital may increase the effects of:

• all other medicaments with sedative effects and cause excessive sedation.

Phenobarbital may decrease the effects of:

• anticoagulants (Coumadin, etc.) and require dose adjustments based on more frequent INR (prothrombin time or protime) testing.
• certain beta blockers (Inderal, Lopressor) and reduce their effectiveness.
• birth control pills (oral contraceptives) and reduce their effectiveness in preventing pregnancy.
• bupropion (Wellbutrin).
• carbamazepine (Tegretol).
• cortisonelike medicaments.
• cyclosporine (Sandimmune).
• delavirdine (Rescriptor).
• dexamethasone.
• diltiazem (Cardizem).
• disopyramide (Norpace).
• donepezil (Aricept).
• doxycycline (Vibramycin).
• felodipine (Plendil).
• griseofulvin (Fulvicin, etc.).
• indinavir (Crixivan) and perhaps other protease inhibitors.
• lamotrigine (Lamictal).
• levonorgestrel (Norplant), requiring alternative birth control.
• metoprolol (Lopressor, others).
• montelukast (Singulair).
• nimodipine (Nimotop).
• quinidine (Quinaglute, etc.) and reduce its effectiveness.
• paroxetine (Paxil).
• propafenone (Rythmol).
• propranolol (Inderal).
• serolimus (Rapamune) or tacrolimus (Prograf).
• ritonavir (Norvir).
• theophyllines (Aminophyllin, Theo-Dur, etc.) and reduce their antiasthmatic effectiveness.
• tretinoin (Vesanoid).
• tricyclic antidepressants.
• verapamil (Calan) and reduce its effectiveness.
• venlafaxine (Effexor).
• warfarin (Coumadin) and increase risk of clots.

Phenobarbital taken concurrently with:

• chloramphenicol (Chloromycetin) may result in decreased chloramphenicol benefits and phenobarbital toxicity-these medicaments are not to be combined.
• colestipol (Colestid) and other cholesterol-lowering resins may bind phenobarbital and limit absorption.
• influenza vaccine may cause phenobarbital toxicity.
• itraconazole (and perhaps other antifungals) may decrease the antifungal effect of itraconazole.
• monoamine oxidase (MAO) inhibitors may lead to excessive lethargy and difficulty talking.
• phenytoin (Dilantin) may alter phenytoin blood levels: a high phenobarbital level will increase the phenytoin level; a low phenobarbital level will decrease the phenytoin level. Periodic determination of blood levels of both medicaments is advised.
• primidone (Mysoline) may lead to phenobarbital toxicity.

The following medicaments may increase the effects of phenobarbital:

• ascorbic acid (vitamin C).
• felbamate (Felbatol).
• valproic acid (Depakene).
• zotepine (Nipolept).

Herbal medicines or minerals:

Using kola or ma huang may result in unacceptable central nervous system stimulation. Since part of the way that ginseng works is as an MAO inhibitor, combination with this medicine is not recommended. Valerian and kava kava may interact to increase drowsiness. St. John's wort may also cause increased sun sensitivity-caution is advised.

Alcohol:

Alcohol can increase greatly the sedative and depressant actions of this medicament on brain functions.

Tobacco smoking:

Smoking may enhance the sedative effects of this medicament and increase drowsiness.

Marijuana smoking:

Increased drowsiness, unsteadiness; significantly impaired mental and physical performance.

Exposure to sun:

This medicament may cause photosensitivity.

Exposure to cold:

Observe the elderly for possible hypothermia while taking this medicament.

Discontinuation:

If used as an anticonvulsant, this medicament must not be stopped abruptly. Sudden withdrawal can precipitate status epilepticus (repetitive seizures). Gradual reduction in dose should be made over a period of 3 months. Total medicament withdrawal may be attempted after a period of 3 to 5 years without a seizure. However, seizures are likely to recur in 40% of adults and in 20-30% of children.

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