Melatonin
N-acetyl-5-methoxytryptamine
Also known as: Regulin · Ferretonin · Dermatonin · Benedorm · Buenas Noches · Cronocaps · HT90 · Melapure · Melatol · Repentil · Revenox · Transzone · Circadin · n-acetyl-5-methoxytryptamine · MLT · pineal hormone · Melatonina
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Alopecia-X, canine pattern baldness, or recurrent flank alopecia (experimental) | One to four 12 mg implants SC. Retreatment may be necessary once or twice a year. Alternatively, 3-6 mg PO q8-12h. | SC/PO | q8-12h (PO) or 1-2 times/year (SC) | — | 🌎 NA |
| Canine recurrent flank alopecia or seasonal flank alopecia | 2-3 mg per dog (up to 10 mg used) | PO | q24h for 3-5 days weekly or monthly, or daily | Improvement usually seen in 1 month, maximal in 3 months | 🌎 NA |
| Alopecia X | 3-6 mg (total dose) | PO | 2-3 times a day | 3 months | 🌎 NA |
| Color dilution alopecia | 1.5-6 mg | PO | 2-3 times a day | Stop when good re-growth occurs | 🌎 NA |
| Alopecia-X | 3 mg-12 mg (depending on size) | PO | 2 to 3 times a day | At least 4 months | 🌎 NA |
| Sleep disorders (nocturnal activity) | 3-6 mg (total dose) | PO | q12-24h | — | 🌎 NA |
| Sleep aid, fears, and phobias | 0.1 mg/kg | PO | q8h | — | 🌎 NA |
| Idiopathic vacuolar hepatopathy | 4-6 mg/day (total dose for dogs <= 15 kg) | PO | q24h | — | 🌎 NA |
| Hair cycling disorders (e.g., Alopecia X, seasonal flank alopecia) | 3-6 mg | PO | q8h | 4-6 week trial | 🌍 EU |
- Alopecia-X, canine pattern baldness, or recurrent flank alopecia (experimental): Recommend having owners sign a release form noting the 'experimental' nature of treatment.
- Alopecia X: Neutering recommended initially. Treat until maximal response is noted and discontinue. Re-institute if signs recur.
- Idiopathic vacuolar hepatopathy: May improve liver enzymes and hepatic changes.
- Hair cycling disorders (e.g., Alopecia X, seasonal flank alopecia): If no growth is noted after 4-6 weeks, discontinue. May need repeating next year for seasonal flank alopecia.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Sleep disorders (nocturnal activity) | 3-12 mg (total dose) | PO | q12-24h | — | 🌎 NA |
| Suppression of estrus | 18 mg implant | SC | Once | Suppresses estrus for 2-4 months | 🌎 NA |
Ferrets
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive treatment of adrenal disease | 0.5-1 mg per ferret | PO | q24h (7-9 hours after sunrise) | — | 🌎 NA |
| Adjunctive treatment of adrenal disease | 1-2 mg per ferret | PO | q24h | — | 🌎 NA |
- Adjunctive treatment of adrenal disease: Can also use 5.4 mg implant which releases over 3-4 months. Better response in fall/winter.
- Adjunctive treatment of adrenal disease: Or use 5.4 mg implant. May cause excessive drowsiness in ferrets under 600 grams.
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Reduction of gastric ulcers in young pigs | 5 mg/kg in feed | PO | Continuous in feed | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Melatonin is a naturally occurring hormone produced by the pineal gland that plays a key role in regulating sleep-wake cycles and photoperiod-dependent functions.
In veterinary medicine, it is primarily used for:
- Dermatologic conditions: Alopecia-X (especially in Nordic breeds), canine pattern baldness, and recurrent flank alopecia.
- Behavioral and sleep disorders: Managing nocturnal pacing/activity in geriatric dogs and cats, as well as phobias and separation anxiety.
- Reproductive management: Reversible estrus suppression in cats and adjusting seasonal fertility in sheep, goats, and horses.
- Endocrine support: Adjunctive treatment for adrenal disease in ferrets.
Clinical Pearl: Melatonin is often considered a safe, first-line, low-cost trial for non-inflammatory alopecias before pursuing more aggressive endocrine diagnostics or treatments.
Mechanism of action
Melatonin is involved in the neuroendocrine control of photoperiod-dependent molting, hair growth, and pelage color.
- Hair Growth: It stimulates winter coat growth; spring shedding occurs when melatonin levels decrease. The exact mechanism is unknown but may involve direct effects on the hair follicle or alteration of prolactin and/or melanocyte-stimulating hormone (MSH) secretion.
- Endocrine Effects: Increases serum prolactin and growth hormone levels, and enhances the response to growth hormone-releasing hormone. Long-term use may decrease luteinizing hormone (LH).
- Antioxidant: Acts as a potent free radical scavenger.
Safety & warnings
Contraindications
- Pregnancy
- Sexually immature animals
- Hepatic insufficiency (in humans)
- No information available
Adverse effects
- Sedation or drowsiness
- Altered sex hormone secretion and fertility
- Sterile abscesses at subcutaneous implant sites
- No information available in monograph (generally well tolerated, may cause mild sedation)
Precautions
Use with caution in patients with renal impairment. Because of its CNS depressant qualities, it should be used cautiously in patients with a history of cerebrovascular disease, depression, or neurological disorders. Animals nursing young may not benefit from implant therapy.
Drug interactions
Melatonin may potentiate sedative effects
Melatonin may potentiate neuromuscular blocking effects
Monitoring
- Clinical efficacy (e.g., hair regrowth, improved sleep patterns)
- Hair regrowth (evaluate after 4-6 weeks of therapy)
Pharmacokinetics
Absorption
No specific information located in veterinary species.
Distribution
No specific information located.
Metabolism
Cleared hepatically (in humans).
Elimination
No specific information located.
Overdose
Little information is available; it is unlikely to cause significant morbidity after a single overdose. Treat symptomatically if profound sedation occurs.
Available products
Formulations
- Oral tablets
- Oral capsules
- Oral liquid
- Subcutaneous implants
- 2 mg tablet
- 3 mg tablet
- Over-the-counter (OTC) formulations of various sizes
Veterinary
- Ferretonin (Melatek) 5.4 mg implant for ferrets
- Dermatonin (Melatek) 8 mg, 12 mg, 18 mg implants for dogs
- Regulin 18 mg implant for sheep/goats
Human-labeled
- Melatonin tablets (0.5 mg to 3 mg)
- Sustained release capsules (3 mg)
- Oral liquid (500 mcg/mL)
- Circadin 2 mg tablets
- Circadin 3 mg tablets
Regulatory status
Circadin is a Prescription Only Medicine (POM)
Circadin is a Prescription Only Medicine (POM)
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature in tight containers unless otherwise labeled.
Client information
Melatonin is a hormone supplement used to treat certain hair loss conditions, sleep problems, and anxiety in pets.
- Administration: Must be given exactly as directed by your veterinarian to be effective, as timing (e.g., giving it at night or a certain number of hours after sunrise) can be important.
- Expectations: For hair loss, it may take several months to see improvement.
- Safety: This use is relatively 'experimental' in veterinary medicine, but it is generally very safe. The most common side effect is mild sleepiness.
- Sourcing: Because it is sold as a supplement over-the-counter, quality can vary. Purchase from reputable brands recommended by your veterinarian.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.