Melatonin
Melatonin is a pineal hormone used empirically for selected hair-cycle and sleep disorders, seasonal reproduction and adjunctive ferret adrenal-disease management. Response and evidence depend on indication.
Group
Indoleamine hormone
Mechanism of Action
Acts at melatonin receptors and influences circadian and follicular signaling.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Alopecia X study regimen | 3 mg/animal | PO | Every 12 h | German Spitz study protocol: 3 months. The corrected amount is per dog, not per kg; efficacy is not established by a protocol alone. |
| Hair-cycle alopecia | 3–6 mg/animal | PO | Every 8–12 h | Empirical regimen; assess response rather than assuming efficacy. |
| Color dilution alopecia | 1.5–6 mg/animal | PO | Every 8–12 h | Empirical regimen; assess response rather than assuming efficacy. |
| Sleep-cycle disturbance | 3–6 mg/animal | PO | Every 12–24 h | Empirical regimen; assess response rather than assuming efficacy. |
| Sleep disturbance or fears and phobias | 0.1 mg/kg | PO | Every 8 h | Empirical adjunct; may cause sedation. |
| Seasonal flank alopecia intermittent regimen | Reference only | PO | A separate regimen uses 2–3 mg per dog once daily for 3–5 days weekly or monthly, or daily; amounts up to 10 mg have been reported. Frequency must be explicitly selected. Improvement may take 1 month and maximum response about 3 months. | |
| Alternative alopecia X trial | Reference only | PO | An empirical size-dependent amount of 3–12 mg per dog 2–3 times daily has been described, with at least 4 months before assessment. Exact size categories are absent; do not apply the maximum indiscriminately. | |
| Alopecia implant treatment | Reference only | SC | One to four 12 mg implants have been described for selected hair-cycle alopecias; retreatment may be needed once or twice yearly. Implant count and timing require an individualized plan. | |
| Idiopathic vacuolar hepatopathy adjunct | Reference only | PO | For dogs at most 15 kg, 4–6 mg total daily has been suggested; evidence of benefit is insufficient. This is a size-qualified empirical plan, not a universal fixed dose. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Sleep-cycle disturbance | 3–12 mg/animal | PO | Every 12–24 h | Empirical total dose; individualize and monitor sedation. |
| Temporary estrus suppression | Reference only | SC | Once | Do not use in: Pregnancy, Sexual immaturity; An 18 mg sustained-release implant suppressed estrus for about 2–4 months in a study. Do not treat pregnant or sexually immature animals with the described implant approach. |
Ferrets
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Adrenal disease adjunct | 0.5–1 mg/animal | PO | Every 24 h | Give 7–9 hours after sunrise. May improve clinical signs, but does not control tumor growth or metastasis. |
| Alternative adrenal disease adjunct | 1–2 mg/animal | PO | Every 24 h | Alternative empirical course; excessive drowsiness can occur below 600 g body weight. Does not control tumor growth. |
| Adrenal disease implant adjunct | Reference only | SC | Once | A 5.4 mg implant releases melatonin over about 3–4 months; may improve signs but not tumor growth. Response varies seasonally. |
Indications
- Selected canine hair-cycle alopecia
- Selected sleep-cycle disturbance
Contraindications
- Products containing xylitol in dogs
Interactions
- Other sedatives may increase drowsiness.
- Benzodiazepines may have additive effects; succinylcholine effects may be potentiated.
Adverse effects
- Sedation
- Lethargy
- Gastrointestinal upset
- Ataxia after excess exposure
Toxicity
Assess all co-ingredients after ingestion; xylitol, 5-HTP and gummy formulations may pose risks beyond melatonin itself.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Melatonin immediate-release tablets 0.5 mg Generic strength described in the supplied material; confirm a single-active, xylitol-free product. Not interchangeable with sustained-release capsules. | Tablet | 0.5 mg / tablet | PO |
| Melatonin immediate-release tablets 1 mg Generic strength described in the supplied material; confirm a single-active, xylitol-free product. Not interchangeable with sustained-release capsules. | Tablet | 1 mg / tablet | PO |
| Melatonin immediate-release tablets 3 mg Generic strength described in the supplied material; confirm a single-active, xylitol-free product. Not interchangeable with sustained-release capsules. | Tablet | 3 mg / tablet | PO |
| Melatonin oral liquid 500 mcg/mL Verify single-active composition and excipients, especially absence of xylitol. | Oral Liquid | 500 mcg / mL | PO |
Monitoring and Administration
Exclude endocrine and other dermatologic causes of alopecia.
A corrected German Spitz research protocol uses 3 mg per dog every 12 hours for 3 months, not 3 mg/kg. It is a study protocol rather than evidence of guaranteed efficacy.
Choose a product without xylitol or other potentially hazardous co-ingredients.
For alopecia, assess response over the specified trial, stop after satisfactory regrowth and restart only for recurrence. Seasonal flank courses of 2–3 months and alopecia X trials of 3 months have been described; do not merge all courses into one duration.
Implant timing for sheep/goat reproductive management depends on latitude, hemisphere, season and breed; a universal calendar is inappropriate. Pig research reports 5 mg/kg in feed but does not establish an individual oral treatment schedule.
Use caution with hepatic dysfunction and renal impairment. Melatonin can alter cortisol and estradiol measurements, fertility and reproductive signaling; implants have caused sterile abscesses. Store in tight containers at room temperature.