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Medication details

  • Medication type: Food supplement, behavior modifier
  • Form: Capsule
  • Prescription required? No
  • FDA approved? Yes (as a food supplement)
  • Life stage: All
  • Brand names: Zylkene
  • Common names: Alpha-casozepine, alpha-S1 tryptic casein
  • Available dosages: 75 mg, 225 mg, 450 mg
  • Expiration range: One year

Has your cat ever demonstrated signs of anxiety? The signs can vary considerably from cat to cat, but may include hiding more often than usual, changes in vocalization, a new onset of aggression, and even changes in litter box habits. This variation in signs can make anxiety difficult to recognize, and the triggers of feline anxiety are often just as variable. Anxiety triggers in cats can range from situational changes (such as moving to a new home or adopting a new pet) to generalized feline anxiety that has no apparent triggers. 

Not only does anxiety have a negative effect on the cat’s quality of life, it can also predispose cats to a number of medical conditions, including lower urinary tract disease. Therefore, owners of anxious cats often consider a variety of solutions to help manage this behavioral issue. While some cat owners immediately consult their veterinarian about the use of a prescription anti-anxiety medication, other cat owners instead try over-the-counter supplements to manage their cat’s anxiety. Zylkene is one of these over-the-counter remedies for feline anxiety. 

What is Zylkene?

Zylkene for cats fod supplement

Zylkene is a nutritional supplement made of alpha-S1 tryptic casein, commonly known as alpha-casozepine. This protein is created by the breakdown of casein, a naturally-occurring protein from cow’s milk. Alpha-casozepine has been shown to have a calming effect and reduce anxiety in a variety of species, including cats. 

Zylkene is a nutritional supplement, not a drug or medication. This means that it is regarded by the US Food and Drug Administration (FDA) as a food. The FDA has placed Zylkene in the category of Generally Recognized as Safe (GRAS) food, but Zylkene has not gone through the same rigorous testing that is required for medications. 

woman with cute cat using laptop at home

You can purchase Zylkene from a wide variety of sources, including veterinary hospitals, pet supply stores, and online retailers. In early 2021, however, the manufacturer of Zylkene (Vetoquinol) released a statement regarding the sale of counterfeit Zylkene through some online retailers. While this counterfeit substance was not associated with any illnesses or injuries in pets, counterfeit substances are often less effective than desired. For this reason, it is safest to purchase Zylkene (as well as other veterinary drugs and supplements) from your veterinarian or from a reputable brick-and-mortar pet supply store. If you have previously purchased Zylkene online and you have any concerns about the validity of your product, contact Vetoquinol Customer Service at 817-529-7500 or customerserviceusa@vetoquinol.com.

What is Zylkene Used For in Cats?

Curious anxious brown tabby kitten portrait

Zylkene is used to treat both short-term and long-term stress in cats (and other species). There are many possible triggers of short-term stress in cats, including travel, veterinary visits, houseguests, a new baby, a new pet, or even moving to a new home. Zylkene can reduce feline stress levels in these situations, allowing your cat to more easily acclimate to a change in circumstances. In cats that are experiencing chronic stress or anxiety, due to their genetics or environment, Zylkene may also offer long-term benefits in stress reduction.

If Zylkene alone is not adequate to treat your cat’s stress, talk to your veterinarian about prescription medications that may be used to address feline anxiety. 

Zylkene Side Effects in Cats

Cat looking sad on top of a couch

Side effects are rarely observed with Zylkene. Unlike medications used to treat anxiety in pets, Zylkene does not have a sedative effect. When side effects do occur, they are typically gastrointestinal in nature. Allergic reactions, which may occur with any medication, are a potential risk with Zylkene but are rare. Given the way that milk proteins are processed in Zylkene, even pets with a dairy allergy should be able to tolerate Zylkene. 

Gastrointestinal effects that may be associated with Zylkene include: 

  • Diarrhea
  • Vomiting
  • Decreased appetite
Veterinarian examining cute cat in clinic

If you notice any of these side effects, stop giving Zylkene and contact your veterinarian. Most adverse effects are very short-lived, because Zylkene is cleared from the body within about 24 hours. However, your veterinarian may still recommend a physical examination and/or treatment, depending on the severity of your cat’s signs.

Zylkene has a wide margin of safety. Contact your veterinarian if an overdose occurs, but negative effects due to overdose are rare. 

Reactions With Other Drugs and Medications

Close up of cat with blue pill capsule

Zylkene can be safely combined with a wide variety of other medications and supplements. There are no known negative interactions between Zylkene and other foods, prescription medications, or over-the-counter medications.

Zylkene Dosage for Cats

Zylkene for cats box

Zylkene dosing is based on your cat’s weight. The following dosages are recommended by the manufacturer: 

  • Cats < 10 pounds: Give one 75 mg capsule once daily. 
  • Cats 11-22 pounds: Give two 75 mg capsules once daily. 
  • Cats > 22 pounds: Give one 225 mg capsule once daily. 

If you are giving Zylkene in anticipation of a stressful event, consider starting this supplement five to seven days before the stressful event. This can help ensure maximal benefits from Zylkene, while also decreasing stress associated with the planning stages of the stressful event (for example, some cats become stressed as soon as their owners pull out a suitcase and start packing for vacation). 

What if My Cat Misses a Dose of Zylkene?

Grey kitten laying down sleepy missed dose

If your cat misses a dose of Zylkene, give the missed dose as soon as possible. If it is already almost time for the next dose when you notice the missed dose, skip the missed dose and resume your regular dosing schedule. 

Price of Zylkene for Cats

The price of Zylkene will depend on your cat’s daily dose. In general, you can expect to pay approximately $25-$50 per month for the long-term administration of Zylkene. There is currently no generic formulation of Zylkene available.

Zylkene Storage Instructions

Black and white domestic cat lying on modern kitchen counter

Zylkene should be stored at room temperature. You can safely store it in a cabinet or on your countertop. Keep this product away from heat and direct sunlight.

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