PHENOBARBITAL
(For veterinary information only)
IMPORTANT NOTE: Please tell the veterinarian that your pet is taking this medication before any surgery.
As with all medications, it is extremely important that this medication be used ONLY for the pet for which it is prescribed.
BRAND NAME: PHENOBARBITAL®
USES OF THIS MEDICATION
Phenobarbital is a sedative in the barbiturate drug class. Most often phenobarbital is used to suppress and prevent epileptic seizures (i.e., seizures for which a cause has not been identified) but phenobarbital can also be used against seizures due to brain tumors, poisonings, or infection as well.
SIDE EFFECTS
Excessive thirst and urination and excessive appetite are not uncommon side effects of phenobarbital. If they occur, they do not generally go away as the pet adjusts to the medication.
It is not unusual for some pets to demonstrate depression or sedation when phenobarbital therapy is initiated. This effect is generally transient and resolves as the pet adjusts to the medication. If this problem has not resolved after two weeks, a phenobarbital blood level can be drawn to determine if the dose is too high for the individual.
Rarely, anemia (lack of red blood cells) can occur with phenobarbital administration. Should this occur, a different antiseizure medication will be prescribed.
Chronic exposure to phenobarbital can lead to scarring in the liver and liver failure that can be irreversible. Proper monitoring tests are employed to prevent this possible side effect.
MONITORING
Since treatment with phenobarbital is
generally long-term, monitoring blood tests are periodically
recommended. When
phenobarbital is started, it usually takes 2-4 weeks to reach a stable blood
level and cannot be fully relied upon to prevent seizures until this period has
elapsed.
It is usual to run a blood phenobarbital level at the end of this period to
determine how the pet is absorbing the medication and whether the dose needs to
be adjusted.
Blood tests should also be done every 6 months to monitor the liver for any damage. Monitoring by periodic blood testing is important in catching any impending liver problems while they are still insignificant.
INTERACTIONS WITH OTHER DRUGS
Chronic administration of phenobarbital makes the liver more efficient at removing other toxins. Other medications which will not work as well in the presence of phenobarbital include: lysodren (treatment for Cushing’s disease), chloramphenicol (an antibiotic), corticosteroids (such as prednisone, dexamethasone), doxycycline (an antibiotic), cardiac beta-blockers, quinidine (a heart rhythm medicine), theophylline (an airway dilator), and metronidazole (a multi-purpose antibiotic/GI medicine). They will not work as well because they are removed from the body much faster than usual by the phenobarbital induced enzymes.
Phenobarbital’s activity can be enhanced by concurrent administration of the following medications: chloramphenicol (an antibiotic), any antihistamine associated with drowsiness, or any other sedative or tranquilizer.
Rifampin, a special antibiotic, may reduce the effectiveness of phenobarbital when the two are used concurrently.
If phenobarbital is used with griseofulvin (treatment for ringworm), the griseofulvin may not be absorbed optimally into the body and may not be as effective.
Phenobarbital may be combined with potassium bromide so that a lower dosage of phenobarbital may be prescribed, while preserving seizure control.
CONCERNS AND CAUTIONS
MISSING EVEN ONE
PHENOBARBITAL DOSE CAN BE ENOUGH TO TRIGGER A SEIZURE.
It is very important to comply fully with medication recommendations.
Phenobarbital should be used with caution in patients with liver disease.
Keep all medicines out of the reach of children.
If you have any questions, please feel free to call us at 672-7800.