Phenobarbital Tablets

Ingredient: Phenobarbital

Appearance: This product is white tablets.

Pharmacological Effects:

Pharmacodynamics

Phenobarbital is a long-acting barbiturate. Its central inhibitory effect varies with dosage, exerting sedative, anticonvulsant and antiepileptic effects, and works for all types of epileptic seizures. It raises the seizure threshold and inhibits the spread of abnormal excitatory signals from lesion foci to surrounding neurons. It achieves remarkable efficacy for grand mal epilepsy and status epilepticus, yet shows poor effect on petit mal epilepsy; monotherapy with phenobarbital may even aggravate petit mal seizures.

It barely inhibits thalamocortical pathways, resulting in weak analgesic activity, but it can potentiate the pain-relieving effect of antipyretic, analgesic and anti-inflammatory drugs.

Pharmacokinetics

Oral absorption of phenobarbital is slow. Its oral bioavailability in dogs reaches 90%, with peak blood concentration achieved 4~8 hours after administration. After absorption, it distributes widely in tissues and body fluids. However, due to low liposolubility, it cannot rapidly cross into the central nervous system like other barbiturates. Onset of action occurs 1~2 hours after oral administration.

It is mainly metabolized via hydroxylation and oxidation in the liver. The elimination half-life ranges from 12~125 hours in dogs (average 2 days), and 34~43 hours in cats. Alkalinizing urine or increasing urine output accelerates its excretion.

Drug Interactions:

1. Phenobarbital acts as a hepatic enzyme inducer. Co-administration accelerates the metabolism and reduces efficacy of the following drugs: aminopyrine, lidocaine, hydrocortisone, dexamethasone, testosterone, estrogen, progesterone, chlorpromazine, doxycycline, digoxin, etc.
2. Combined use with other central depressants (general anesthetics, antihistamines, sedatives) will intensify central nervous system suppression.
3. Co-administration with sulfonamides displaces phenobarbital from plasma protein binding sites, enhancing its pharmacological effect.
4. Drugs that alkalinize blood and urine can speed up renal excretion of phenobarbital.

Actions and Indications:

Barbiturate. Used to relieve convulsions caused by encephalitis, tetanus and strychnine poisoning.

Dosage and Administration:

Oral use: Single dose of 6~12mg per kg body weight for dogs and cats, or as directed by a veterinarian.

Adverse Reactions:

1. Dogs may occasionally present depression, restlessness or ataxia.
2. Cats are sensitive to phenobarbital and prone to respiratory depression.

Precautions:

1. Contraindicated in animals with liver or renal insufficiency, bronchial asthma or respiratory depression. Use with caution in severely anemic, cardiac and pregnant animals.

2. Central stimulants such as caffeine sodium benzoate, pentetrazole and nikethamide can be used for rescue in cases of poisoning.

3. For early oral poisoning: Gastric lavage with 1: 2000 potassium permanganate solution, followed by sodium sulfate for catharsis (magnesium sulfate is forbidden). Sodium bicarbonate shall be used to alkalinize urine to accelerate drug excretion.

Withdrawal Period: No required.

Specification: 30mg

Package: 

(1) 6tablets/box (2) 12tablets/box (3) 18tablets/box (4) 24tablets/box

(5) 30tablets/box (6) 36tablets/box

Storage: Store in a tightly sealed container.

Shelf Life: 24months