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Phenobarbital for Cats: Overview, Dosage & Side Effects

Phenobarbital is an anti-convulsant medication used commonly in veterinary medicine to help manage conditions that cause seizures. In this article youll learn how phenobarbital treats patients suffering from a seizure disorder, side effects to watch for, and some frequently asked questions.

Phenobarbital for Cats Overview

Medication Type:

Barbiturate

Form:

Tablets, oral solution, injection.

Prescription Required?:

Yes

Brand Names:

Luminal, solfoton

Common Names:

Phenobarbital, phenobarbitone

Available Dosages:

Tablets in 15mg, 16.2mg (1/4 grain), 30mg, 32.4mg (1/2 grain), 60mg, 64.8mg (1 grain), 90mg, 97.2mg (1.5 grains), and 100mg. Oral solution: 20mg/5ml (4mg/ml).

Expiration Range:

Tablets should be stored in light-resistant containers at room temperature (20 to 25 degrees C or 68-77degrees F). Protect from moisture. Products should be used before the expiration date on the package.

About Phenobarbital for Cats

Phenobarbital is a barbiturate medication. Barbiturates are a class of drugs that act as central nervous system (CNS) depressants. They can be used as sedatives, to treat anxiety, and to control seizure disorders.

A seizure occurs when a sudden discharge of electrical signals occurs in the brain that leads to involuntary activity of the body, or seizing.

Patients experiencing a seizure often lose consciousness and the body may then exhibit the appearance of muscle spasms or convulsions, or a pet may go completely rigid with stiff muscles. Drooling, urination, and defecation may also occur.

Seizures can occur for a variety of reasons. The presence of brain tumors and inflammatory lesions in the brain can be one set of causes where something structurally abnormal is present. Pets may also develop seizures from certain underlying medical disorders like liver and kidney disease, toxin ingestion, or if a diabetic cats blood sugar goes too low.

But seizures can also occur secondary to a condition known as idiopathic epilepsy. With epilepsy, the neurologic overexcitement occurs leading to a seizure, but there is no known cause. Pets with epilepsy often have normal MRI (magnetic resonance imaging) scans of the brain.

As an anticonvulsant medication, phenobarbital helps to reduce the chance of a seizure occurring by reducing the abnormal electrical activity that leads to seizure episodes. There are several types of antiseizure medications available, each working in a different way, with some more effective in some cases than others.

Phenobarbital is one of the oldest antiseizure/antiepileptic drugs available for treating cats with seizure disorders.

What Does Phenobarbital Do for Cats?

Barbiturates like phenobarbital generally cause depression of the central nervous system (CNS). They can inhibit a few different neurotransmitters, including acetylcholine, norepinephrine, and glutamate. Their actions raise the seizure threshold, requiring a lot more electrical overexcitement in the brain to have to occur to cause a seizure. This generally reduces the frequency of seizure events.

The degree of CNS depression phenobarbital causes depends on its dose. Their effects can also depend on a patients age, physical condition, and other medications being taken.

Although it has been around for a long time, phenobarbital is still one of the best medications to be used as a primary drug, or monotherapy, for a seizure condition. It tends to be more effective as a first-line choice compared to some other anti-seizure medications like zonisamide and potassium bromide.

Phenobarbital is also very inexpensive, making it a preference in some cases, especially for long-term use, compared to an effective but much pricier anti-seizure medication like Keppra (levetiracetam).

Side Effects of Phenobarbital for Cats

One common side effect of phenobarbital is excessive drinking and urination.

The most common adverse effects seen in cats on phenobarbital include balance issues when walking, drowsiness, facial itching, an excessive need to eat (leading to weight gain), and excessive drinking and urinating.

While very rare, immune-mediated reactions like reduced white blood cell and platelet counts have been described.

Because it depresses the central nervous system, respiratory depression (ineffective breathing) can occur. Cats appear to be more sensitive to this effect, though it is still typically only seen at higher doses.

Phenobarbital is largely metabolized by the liver. Unlike in dogs, who commonly have liver value elevations on their bloodwork, at least for the first couple of weeks when starting phenobarbital, cats do not appear to have the same sensitivity and liver value abnormalities are considered rare in kitties.

All the same, phenobarbital should be used with great caution in any cat with an underlying liver disorder. Because of the importance of having good liver function on this medication, veterinarians commonly check blood work prior to starting phenobarbital and then at least every six months thereafter.

Phenobarbital should also be used cautiously in any cat that is in a state of dehydration, has a low red cell count (anemia), cardiac disease, or respiratory disease.

While phenobarbital does not have direct effects on the kidneys, its effects on lowering blood pressure, which is called hypotension, can lead to concerns with renal function if pressure within the kidneys drops too low. This is typically also more a concern with high doses and overdoses.

When first starting phenobarbital, it is common to see excessive sleepiness, lack of energy, greater thirst and appetite, and an increased need to urinate. These signs typically abate after about three to four weeks.

In overdose situations, a majority of cats show signs of difficulty walking or keeping their balance and lethargy/sedation.

Phenobarbital can have drug interactions with other medications. For cats, common ones may include the appetite stimulant mirtazapine, the sedative dexmedetomidine, and opioids like buprenorphine, which should be used cautiously. Use with antihistamines may also increase the sedative effect.

There are many medications where concurrent phenobarbital use will decrease their effectiveness and their doses may need adjustment when starting phenobarbital or vice versa. Always make sure to discuss any medications or supplements your cat is currently taking when starting phenobarbital is being considered.

If you are ever concerned that your kitty may have developed side effects while using phenobarbital, or if an overdose is suspected, make sure to contact your primary veterinarian, neurology veterinarian, the ASPCA Animal Poison Control Center (1-888-426-4435) or Pet Poison Helpline (1-855-764-7661) immediately for further advice.

Phenobarbital for Cats Dosage

Though phenobarbital is considered a safe medication for cats, it can pose significant concerns if dosed too high, overdosed, or when it is improperly used.

Phenobarbital is used in an extra-label manner, meaning that it does not carry an FDA label, but a veterinarian can still prescribe it as long as an active relationship with the patient is present. This is very common when medications also used for humans are used in pets.

Phenobarbital is a schedule IV controlled substance. This means that at least in humans, it has some potential for abuse, and prescribed amounts and refills are carefully monitored.

Phenobarbital is prescribed for people with seizure and sleep disorders. It is extremely important to never use any medication you may have at home in your cat. Human doses and cat doses of a common medication may differ significantly and serious side effects could result.

Phenobarbital is considered a safe medication for cats when dosed properly, but can have significant concerns when dosed too high, overdosed, or when it is improperly used.

For these reasons, a specific dose for phenobarbital is not provided here. It is very important to always consult with your veterinarian before starting a medication like phenobarbital.

Its also important to not give your cat an extra dose of phenobarbital or to alter the dose yourself if a seizure event has recently occurred. If your cat is actively having a seizure, it is most important to get your kitty to the nearest veterinary hospital for treatment. Never try to administer an oral medication to a pet that is actively seizing.

Safe use of phenobarbital involves checking the blood levels of the medication in the body through blood work. This is commonly recommended every six months. This is the best way to know if the drug is maintaining therapeutic levels, what dosage is most effective, and whether any adjustments need to be made. Serum phenobarbital levels should always be rechecked after any dosage adjustments.

Phenobarbital may be given with or without food. However, if any digestive upset occurs, giving with food may help.

Phenobarbital should not be discontinued abruptly as this can lead to withdrawal syndrome. This can be the case if a kitty has been on the medication for even just a few weeks. The medication is typically weaned slowly to help the body adjust. Weaning slowly is also important because seizures may recur if the medication is discontinued too quickly. Another medication to control seizures will typically need to be started at the same time that phenobarbital is being weaned.

Conclusion

Phenobarbital is a long-standing medication for control of seizures in cats and it is typically very effective at controlling seizures. It is also very inexpensive. It does have some expected side effects to monitor for when first starting it, especially lethargy, increased appetite, excessive water consumption, and urination changes, but many of these dissipate after a few weeks. It does require more frequent blood work monitoring than some other medications.

Phenobarbital can also have many interactions with other medications that may require dose adjustments. Always make sure to discuss your cats medical history and other medications thoroughly with your veterinarian before starting phenobarbital for the best and most cautious approach to your cats health care.

Frequently Asked Questions

What does phenobarbital do to cats?

Phenobarbital is used primarily as an anti-seizure medication in cats. It raises the seizure threshold and reduces seizure frequency by acting as a depressant of the central nervous system (CNS).

With proper dosing, phenobarbital is very effective at controlling seizures. However, at higher doses, the CNS depression can lead to more concerning effects like sedation, lethargy, respiratory depression, and low blood pressure. This is why careful and accurate dosing by a veterinarian is very important.

How long can a cat live on phenobarbital?

This may depend more on the primary cause for a seizure disorder, as well as the general state of health of a particular kitty. In a cat that is otherwise healthy, and has, say idiopathic epilepsy, a normal life expectancy may be possible. Liver toxicity has not been described in cats like it has in dogs, and with proper dosing they can tolerate the medication fairly well.

However, in a cat with concomitant liver disease or other health concerns, phenobarbital may manage seizures well, but also contribute to more significant side effects. If a cat is suspected to have a cancerous tumor causing seizures, phenobarbital will still control signs at least initially, but a kittys prognosis would be more linked to the nature of the type of cancer.

How long does it take phenobarbital to work in cats?

Phenobarbital can take a few hours to reach its peak effectiveness. This may take anywhere from four to 12 hours when dosed orally.

After starting phenobarbital or making dose changes, blood serum levels may not be checked for a couple of weeks, as it does take some time for the body to adjust to the medication.

Can phenobarbital cause death in cats?

This is very uncommon, but in theory could occur if a very high dose is given or if a cat in an ill or sick state is given the medication. Fortunately, most cases of cats getting an overdose of phenobarbital that have been reported to the ASPCA Animal Poison Control Center only exhibited signs of lethargy and ataxia (balance and walking issues).

Cats do appear to be more sensitive to the respiratory depression effects of phenobarbital when given at higher doses.

Phenobarbital should not be confused with pentobarbital, which is commonly used as a euthanasia drug in veterinary medicine. While they are both barbiturates, pentobarbital is more potent than phenobarbital. Pentobarbital also does not come in any oral administration forms.

Solensia for Cats: Overview, Dosage & Side Effects

Solensia is an injectable medication thats FDA-approved for use in cats to bring relief from arthritis pain. In this article, youll learn what Solensia is, how it works, potential side effects, and frequently asked questions.

Solensia for Cats Overview

Medication Type:

Felinized monoclonal antibiody targeting NGF

Prescription Required?:

Yes

Life Stage:

Cats and kittens 7 mo of age and older.

Common Names:

Frunevetmab

Available Dosages:

1ml vial containing 7mg of frunevetmab

Expiration Range:

Contents of the vial must be used immediately once punctured.

About Solensia for Cats

The brand name for frunevetmab, Solensia is a drug used to help cats with osteoarthritis.

Solensia is a brand name for frunevetmab, manufactured by Zoetis. Frunevetmab is a felinized immunoglobulin monoclonal antibody.

An antibody is a protein created by the immune system to target a particular substance. Usually, we think about antibodies against something like a virus, which helps the body avoid or quickly eliminate a viral infection.

A monoclonal antibody is a synthetic antibody that is designed to target only one specific substance. Felinized simply means that the monoclonal antibody is designed to work specifically in a cats body and cannot be used in other animal species.

As a monoclonal antibody, Solensias target substance is something called nerve growth factor (NGF). In adult animals, NGF is elevated in response to injury, disease, and noxious stimuli and contributes to neurogenic inflammation and increased perception of pain.

NGF has been found in both humans and other animal species to be involved with types of chronic pain, such as that caused by osteoarthritis (OA), where NGF has been found to be elevated in arthritic joints.

Frunevetmab works by binding to NGF, thereby preventing NGF from binding to other receptors that are involved with furthering signals of pain and inflammation.

Solensia is FDA-approved for use in cats specifically for the treatment of pain associated with feline osteoarthritis. It is available only as an injection that is given under the skin at a veterinary clinic once a month.

Also Read:Arthritis In Cats: Causes, Symptoms, & Treatment

What Does Solensia Do for Cats?

By binding to nerve growth factor (NGF) and preventing it from binding to receptors involved in the pain response, Solensia helps to keep your cat from experiencing the pain associated with osteoarthritis.

In recent years, it has become more apparent through research studies that osteoarthritis (OA) is more common in cats than previously thought. Studies have shown that although cats may have x-ray evidence of arthritis, far fewer of those cats show obvious signs of pain and decreased mobility at home. This can make arthritis in cats difficult to appreciate at home, or diagnose during veterinary visits.

But the treatment of arthritis is also challenging for cats and their caretakers. No non-steroidal anti-inflammatory (NSAID) medication is approved for safe long-term use in cats, and the use of steroids has fallen out of favor given the association between long-term use and a higher risk of side effects.

Pain medications, like gabapentin or buprenorphine, may often be considered. But while they can reduce pain and help with comfort, they do not target the underlying joint inflammation causing the pain.

Orally medicating cats can also be challenging, so even in cases where a pain medication, such as gabapentin, can be used long-term to manage pain, the high affinity for many cats to sniff out medication hidden in food or treats as well as the difficulty of pilling/medicating directly by mouth can lead to major consistency problems with treatment at home.

Solensia provides a potential solution to many of these concerns with a focused drug that appears to be very well tolerated for longer-term use, even in older cats, as well as eliminating the oral route entirely since the injection must be given at the vets office.

According to early studies, a single Solensia injection provided significant pain relief as evidenced by increased activity for up to 6 weeks in cats with degenerative joint disease (DJD). Based on owner assessments alone, about of cats receiving 3 doses of Solensia were considered to be treatment successes.

While still a newer product as of the time of this writing, Solensia appears to be the first drug of its kind that can be tolerated by cats for long-term use for joint pain and inflammation with the added bonus of eliminating the stress and compliance issues of medicating at home.

Also Read:12 Warning Signs Your Cat Is In Pain And Crying For Help

Side Effects of Solensia for Cats

Several side effects have been reported for Solensia for cats.

Solensia has not been evaluated in cats less than 7 months of age or weighing less than 5.5 lb (2.5kg).

In cats, gastrointestinal signs appear to be the most commonly reported, though still relatively uncommon. According to the manufacturer, in a field trial involving nearly 200 cats over the course of about 3-4 months, vomiting was the most often reported at 13%. Diarrhea and loss of appetite were the next most common, at about 6.5%.

Injection site discomfort was noted in about 11% of cats. This was further explained to be seen as flinching noted occasionally, and most frequently with the first dose.

Local reactions at the injection site were reported in about 3-6% of cats. These reactions included scabbing, red skin, hair loss, swelling at the site, and itching/scratching.

Abnormal behavior was noted in about 6.5% of cats. This was clarified to be behavior recorded as being abnormal for the individual cat (about 12 of them in the study) but not any kind of recognized disorder.

Early studies for Solensia appear to largely demonstrate safety for cats in terms of kidney function, including cats with early-stage IRIS 1 or 2 of chronic kidney disease, though a small number of cats did have some mild changes in kidney lab parameters.

Twelve of the cats in the study showed evidence on lab work of worsening of existing mild kidney disease. In a separate safety study looking at Solensia use in a small group of very young cats, bloodwork creatinine values were seen to increase within the normal range, but never exceeded the upper limit of normal.

In a pilot clinical study published in Frontiers in Veterinary Science in 2021 titled Efficacy and Safety of an Anti-nerve Growth Factor Antibody (Frunevetmab) for the Treatment of Degenerative Joint Disease-Associated Chronic Pain in Cats: A Multisite Pilot Field Study, Solensia was used in 126 client-owned cats with a mean age of 12-13 years. The authors indicated that about half of the cats in the study, just given their age, were in stage II of chronic kidney disease.

Of those cats in the study receiving Solensia injections, two had elevations in lab work parameters while still staying at the same level of kidney disease, with one cat increasing to stage 3 of kidney disease.

Other side effects mentioned by the manufacturer were seen in about 4% or less of cats.

As of this writing, Solensia has not been studied in combination with other medications, including NSAIDs.

Solensia should not be used in pregnant or lactating queens.

If you are ever concerned that your kitty may have developed side effects following a Solensia injection, make sure to contact your veterinarian, the ASPCA Animal Poison Control Center (1-888-426-4435), or Pet Poison Helpline (1-855-764-7661) immediately for further advice.

The use of monoclonal antibodies is relatively new within the last several years but shows much promise in both human and animal medicine. However, a phenomenon called immunogenicity has been seen. Immunogenicity occurs when a patients body develops its own antibodies to the monoclonal antibody drug, thereby making the drug less effective over time.

In a study mentioned by the manufacturer, immunogenicity was detected in only 4 cats out of about 260 total cats.

Also Read:The Best Homemade Cat Food Recipes For Kidney Disease

Solensia for Cats Dosage

Solensia must be administered by a veterinarian or a trained veterinary staff member under a vets supervision.

Solensia is FDA-approved for use in cats, but can only be administered legally by a veterinarian or a trained veterinary staff member under the supervision of a DVM.

Dosing of Solensia is based on weight and is injected subcutaneously under the skin once a month. Each 1ml vial of Solensia contains 7 mg of frunevetmab. Cats weighing 5.5 to 15.4 lb (2.5-7 kg) receive one vial with cats exceeding 15.5 lb receiving two vials.

Following an initial dose, Solensia is designed to be continued as a monthly injection.

Also Read:What Can You Give A Cat For Pain? 6 Vet-Recommended Options

Conclusion

A relatively new medication at the time of this writing, Solensia is approved for use in cats to help ease pain and inflammation in cats with osteoarthritis.

Solensia is an injectable medication approved for use in cats to treat osteoarthritis. It provides the only current longer-term treatment option for cats that can address both pain and components of inflammation arthritis causes.

The long-acting injection also eliminates the need for oral dosing, which can be difficult for many kitties and their caretakers. Though it is still relatively new, early pilot field and safety studies suggest Solensia has a favorable safety profile.

Also Read:Drug Poisoning In Cats: Causes, Symptoms, & Treatment

Frequently Asked Questions

How Long Does It Take Solensia to Work in Cats?

The pain relieving effects of Solensia have been described by cat owners in studies to be apparent after about 2-3 weeks after administration. This would be expected after the first, initial dose. If Solensia is continued long term, consistent pain relief would be expected.

Is Solensia Available Yet for Cats?

Yes. The FDA gave approval of Solensia on January 13, 2022 and is currently available for use in cats. However, since it is a relatively new drug, not all veterinary practices may currently carry it yet.

How is Solensia Administered to Cats?

Solensia is administered to cats as a subcutaneous injection under the skin. It is only approved for administration by, or under the direct supervision of, a licensed veterinarian and is administered to a cat during the course of a veterinary visit.

Is Solensia an Anti-inflammatory?

Solensia (frunevetmab) is not an anti-inflammatory in the traditional sense, as it is not a steroid or a non-steroidal anti-inflammatory drug (NSAID). However, its action as a monoclonal antibody (mAb) does have some anti-inflammatory effect.

The target of frunevetmab for treating feline osteoarthritis (OA) is felinized nerve-growth factor (NGF). In adult cats, NGF is not only involved with the bodys perception of pain and noxious stimuli, but it also assists in the release and perpetuation of certain inflammatory mediators that further inflammation in the body. When frunevetmab as a monoclonal antibody binds to NGF, it not only reduces the sensation of cat OA pain but also interferes with the continuation of inflammation that NGF contributes to.