Vetoquinol Zylkene Calming Support Supplement for Large Dogs 33-132lbs, Promotes Relaxation, Reduces Stress, and Supports Occasional Anxiety Relief for Dogs, 450mg - 30 Capsules Review
By Marcus Bell · Dog nutrition editor · Published 2026-05-20 · Updated 2026-07-01
3.9(1,000)Amazon rating$76.99400+ bought last month
Our verdict
Vetoquinol Zylkene is a capsule supplement built around alpha-casozepine, a milk protein derived calming compound, dosed at 450 mg for large dogs between 33 and 132 pounds, and its 3.9 star average across roughly 1,000 reviews puts it solidly in the middle of this category.
Large dog owners looking for a flavorless capsule supplement for triggers like moving, travel, thunderstorms, or general stress.
Skip if
You have a small or medium dog, since this 450 mg strength is specifically dosed for dogs between 33 and 132 pounds, or you're looking for a lower-cost option since this is one of the pricier products in the silo.
Form Capsule
Flavor Flavorless
Benefits Calming Support
Best for Anxiety, Moving, Stress, Thunderstorms
Breed size Large
Weight 0.05 Pounds
Priced 221% above the category median ($23.99 across 63 tracked models)
Our scorecard
3.9/5overall
Owner rating3.9/5
3.9 average across 1,000 owner ratings
Popularity2.9/5
1,000 owner reviews, more than most models here
The overall score is owner satisfaction weighted by how many reviews back it, so a high rating from few reviews counts for less. The bars below show where this model stands against the other dog food and health supplements we track in this category on price, popularity and size. Context, not marks against it, and our read of the data, not a lab test.
Overview
["Zylkene's active ingredient is alpha-casozepine, derived from hydrolyzed bovine milk protein, delivered here in a 450 mg capsule sized for large dogs between 33 and 132 pounds. Vetoquinol positions it for anxiety, moving, general stress, and thunderstorms specifically, rather than as a broad catch-all calming product.", "Because it's flavorless and comes as a capsule, it can be opened and mixed into food for dogs that won't take a pill directly, though it won't have the treat-like draw of a flavored soft chew. The 30-capsule count is a relatively short supply for a large dog used daily, which is a factor worth weighing against the price.", "At $76.99, this is one of the more expensive products in the entire calming silo, reflecting its capsule format and large-dog dosing strength. It's built a smaller review base of roughly 1,000 reviews at a 3.9 star average, with about 400 units bought in the past month, a more modest volume than the leading chew brands."]
Pros
Named active ingredient (alpha-casozepine from hydrolyzed milk protein) at a clear 450 mg dose
Sized specifically for large dogs between 33 and 132 lbs
Flavorless capsule can be opened and mixed into food
Targeted specific uses listed: anxiety, moving, stress, thunderstorms
Cons
One of the priciest products in this category at $76.99
3.9 star average trails several other calming products in this silo
30-capsule count may not last long for daily use in a large dog
Flavorless capsule lacks the treat appeal of a soft chew
Specifications
Form
Capsule
Flavor
Flavorless
Benefits
Calming Support
Best for
Anxiety, Moving, Stress, Thunderstorms
Breed size
Large
Weight
0.05 Pounds
Performance notes
The 450 mg alpha-casozepine dose is specifically formulated for large-breed dosing (33 to 132 lbs), which is a narrower, more targeted approach than the general all-breed chews common elsewhere in this silo. Being a flavorless capsule rather than a chew means it can be split open and mixed into wet food for dogs that resist taking a pill.
What buyers say
A 3.9 star average across roughly 1,000 reviews and about 400 units sold in the past month suggests a smaller but consistent base of large-dog owners, likely drawn by the specific alpha-casozepine dosing rather than a general calming chew.
What is alpha-casozepine and how is it delivered here?
It's a compound derived from hydrolyzed bovine milk protein, delivered in this product as a 450 mg flavorless capsule sized specifically for large dogs between 33 and 132 pounds.
Can I open the capsule and mix it into my dog's food?
The capsule is flavorless, which makes it a reasonable option to open and mix into food for dogs that won't take a pill directly, though you should follow the label's dosing directions.
Is this meant for daily use or just specific events?
Vetoquinol lists it for anxiety, moving, general stress, and thunderstorms, so it can be used either around specific triggers or more regularly, but with only 30 capsules per box, check how that fits your dog's dosing schedule.
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