Hepatotoxicity. Prospective studies suggest that less than 1% of subjects develop elevations in serum aminotransferase levels during long term phenobarbital therapy. Clinically apparent hepatotoxicity from phenobarbital is rare but can be abrupt in onset, severe and even fatal.
What does phenobarbital do to the liver?
Phenobarbital causes a marked proliferation of the smooth-surfaced membranes of the endoplasmic reticulum in the liver cells. And, like many other compounds, it is an inducer of drug-metabolizing enzyme systems in the hepatic microsomes.
What are the signs of liver toxicity in dogs?
Signs that a dog has liver disease can vary and include loss of appetite, vomiting, stomach ulceration, diarrhea, seizures or other neurologic problems, fever, blood clotting problems, jaundice (a yellow tinge noticeable in the skin, mucous membranes, and eyes), fluid collection in the abdomen, excessive urination and …
Is phenobarbital metabolized by the liver?
Approximately 20%–40% of a given dose of phenobarbital is excreted unchanged in urine; the rest is slowly metabolized in the liver. The excretion of phenobarbital is considerably higher when the pH of urine is alkaline. The half-life of phenobarbital in serum is 50–160 h in adults; in children, it is shorter (30–70 h).
Can phenobarbital cause liver failure in dogs?
Long-term administration of phenobarbital has been reported to cause hepatic injury in dogs. Phenobarbital induces hepatic enzymes, and it may be difficult to distinguish the effect of enzyme induction on serum liver enzyme activities from actual hepatic damage.
What are the side effects of phenobarbital in dogs?
Common short-term side effects of phenobarbital are mild sedation and some incoordination. Longer term side effects may be increased appetite, and, occasionally, increased thirst and urination. After 7-10 days, these effects wear off and your pet should appear normal again.
Can phenobarbital cause liver damage in dogs?
What drugs cause liver damage in dogs?
Many drugs have been suspected of causing hepatic injury in dogs and cats. Most adverse hepatic drug reactions are associated with acute hepatic injury. However, some drugs, most notably Phenobarbital, lomustine, oxibendazole/DEC (and possibly carprofen and amiodarone) may be a cause of chronic hepatic injury.
How is phenobarbital metabolized?
Phenobarbital is metabolized in the liver by CYP2C9 with minor metabolism by CYP2C19 and CYP2E1. A quarter of the dose of phenobarbital is excreted unchanged in the urine. In adults, the half-life of phenobarbital is 100 hours and in term and preterm infants is 103 and 141 hours, respectively.
How long does it take for phenobarbital to get into a dog’s system?
In about 2 weeks, a “steady state” or plateau level of drug in the bloodstream is reached, which is why we recommend a level check at this time.
How does phenobarbital affect dogs?
Phenobarbital works by decreasing and stabilizing neuron activity in the brain. It increases the neurotransmitter GABA, which calms nerves, and decreases glutamate, a neurotransmitter that stimulates nerves. While this decreases seizuresin dogs, it can also lead to some unintended side effects, such as lethargy and sedation.
Is phenobarbital safe for dogs?
While phenobarbital is generally safe and well tolerated, it can produce side effects. The most common side effects of Phenobarbital in dogs are: Increased urination (this is usually in response to increased drinking) Weakness and loss of coordination in the hind legs (known as ataxia)
Does phenobarbital cause incontinence in dogs?
Phenobarbital has also been known to cause agitation and/or aggression in a small percentage of dogs. If your dog experiences these side effects, be sure to advise your veterinarian so that adjustments to the medication can be made.
