Alpha-casozepine has shown modest supportive effects on stress- and anxiety-related behavior in dogs, including in controlled studies. Recent veterinary-visit trials found lower behavioral stress scores or fewer fear-related postures after treatment.
The evidence is not uniformly positive across every outcome. Cortisol, heart rate and other physiological measures have often changed little or inconsistently, and several older studies tested alpha-casozepine alongside behavioral management or as part of a complete diet.
What is alpha-casozepine?
Alpha-casozepine is a bioactive peptide associated with hydrolysis of bovine αs1-casein. Defined alpha-casozepine preparations should not automatically be treated as equivalent to generic casein, hydrolyzed milk protein or any product containing “milk protein.”
Exact preparation identity matters.
What did the early clinical study show?
In 2007, dogs with anxiety-related disorders received alpha-casozepine or selegiline, with individualized behavioral modification in both groups. Both groups improved, with no significant difference between treatments.
This is supportive evidence, but there was no placebo group. The study cannot establish how much improvement came from the supplement versus behavioral modification or nonspecific change.
What did the 2024 veterinary-visit trial show?
A randomized placebo-controlled study gave casozepine (36 dogs) or placebo (26 dogs) for two days before a standardized veterinary examination. At the follow-up examination, the casozepine group had lower veterinarian stress scores and lower mean and maximum pulse rates than the placebo group. Salivary vasopressin rose in the placebo group but not in the casozepine group, while cortisol rose in the casozepine group, so the hormone results did not provide a consistent supportive signal.
The authors characterized the effect as weak stress reduction rather than a dramatic anxiolytic response.
What did the newer crossover study show?
Twenty privately owned dogs with mild-to-moderate situational fear/anxiety received alpha-casozepine 15 mg/kg orally every 24 hours for six days or placebo before veterinary visits in a blinded crossover design.
Alpha-casozepine reduced several fear-related postures and increased olfactory exploration. Veterinarians also gave lower stress scores. There were no significant treatment effects on heart rate, respiratory rate, heart-rate variability or rectal temperature.
This supports a behavioral anxiolytic-like effect in that specific context, without evidence of broad autonomic normalization.
Does alpha-casozepine sedate dogs?
The literature is better described in terms of reduced stress- or anxiety-related behavior than sedation. Increased exploration alongside fewer fear postures is not the same as simply making a dog drowsy.
Unless sedation is specifically measured and demonstrated, reduced fear behavior should not be converted into a sedation claim.
Can veterinary-visit evidence be generalized?
No. Veterinary visits, thunderstorms, fireworks, separation-related distress and travel involve different triggers. Evidence from one context should not silently become evidence for all canine anxiety.
Likewise, a trial of alpha-casozepine plus tryptophan or another active ingredient is combination-formula evidence, not proof for alpha-casozepine alone.
Dog Supplement Facts evidence status
VERIFIED_SUPPORTIVE
Controlled canine studies provide repeated supportive behavioral signals for defined alpha-casozepine preparations. Confidence is moderated by modest sample sizes, heterogeneous designs, combination formulas in some older studies and inconsistent physiological endpoints.
The correct wording is modest, preparation-specific and context-specific support, not “proven calming ingredient.”
Related Dog Supplement Facts content
- Dog Calming & Stress Guide
- Do Calming Chews for Dogs Work?
- How to Check a Dog Calming Supplement Label
In our comparison: products that list alpha-casozepine (milk protein)
2 of the 221 dog calming & stress products we compared list alpha-casozepine (milk protein) (1%). None of them is among the 20 most popular products, and their median popularity rank is #33 of 188 ranked products. Our ingredient-level evidence rating for alpha-casozepine (milk protein): supportive.
Product-level ratings, which look at the whole formula: 1 supportive, 1 mixed.
Most popular of these:
- #33Vetoquinol Zylkene, Calming Capsules for Small Dogs & Cats, 120 Capsules — Supportive
- #183Vetoquinol Zylkene Plus Calming Supplement for Medium Dogs and Cats, 225 mg — Mixed
See all 2 in the comparison table →Best sellers vs the evidence
Popularity is a relative rank within our comparison (purchases, review volume and star rating), not Amazon's Best Sellers Rank and not a measure of effectiveness. Listing data collected September 2026.
Frequently asked questions
Does alpha-casozepine work for dogs?
Controlled studies show modest reductions in stress-related behavior in specific situations, such as fewer fear-related postures during veterinary visits. Heart rate, cortisol and other physiological measures changed little or inconsistently.
What dose of alpha-casozepine was used in dog studies?
A recent crossover study gave 15 mg/kg by mouth once a day for six days before veterinary visits. Follow the product label and ask your veterinarian before relying on it.
Does alpha-casozepine make dogs sleepy?
The studies describe fewer fear behaviors and more exploring, not sedation. Unless drowsiness is measured, a calmer dog should not be assumed to be a sedated one.
Is alpha-casozepine the same as milk protein?
No. Alpha-casozepine is a specific peptide from hydrolyzed bovine casein. Generic casein or hydrolyzed milk protein is not equivalent to the defined preparations that were studied.
References
- Beata C, Beaumont-Graff E, Diaz C, et al. Journal of Veterinary Behavior. 2007;2(5):175–183. doi:10.1016/j.jveb.2007.08.001.
- Palestrini C, Minero M, Cannas S, et al. Journal of Veterinary Behavior. 2010;5(6):309–317. doi:10.1016/j.jveb.2010.04.004.
- Schroers M, Juhasz A, Zablotski Y, Meyer-Lindenberg A. The Veterinary Journal. 2024;306:106148. doi:10.1016/j.tvjl.2024.106148.
- Puglisi I, Masucci M, Siracusa C. Journal of Veterinary Behavior. doi:10.1016/j.jveb.2025.12.008.