Melatonin (brand names: Regulin®, Circadin®) is a hormone supplement commonly used in humans to regulate the sleep cycle. In veterinary medicine, it is used off label (extra label) in a variety of ways:
In dogs, melatonin is used to treat sleep and behavior disorders and non-allergic hair loss (alopecia). In cats, melatonin is used to treat sleep and behavior disorders and to suppress the heat (estrus) cycle. In horses, melatonin is used to improve breeding rates. In ferrets, melatonin is used to treat adrenal disease.
Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
Melatonin supplements marketed for humans may be used off label in pets. However, caution is advised, as human products may contain xylitol, which is toxic to dogs. Sustained-release oral melatonin products should not be used off label in pets.
In some countries, melatonin is available in an implant form, to be placed under the skin. In the U.S., the only FDA-approved use of melatonin in animals is for these implants in mink (Mustela vison), to accelerate the fur priming cycle. The information in this handout is specific to oral melatonin supplements.
Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
The U.S. Food and Drug Administration (FDA) does not review non-drug health supplements (e.g., herbals, nutraceuticals, shampoos, and other supplements) for safety or effectiveness before they are sold to the public. Manufacturers of non-drug health supplements must ensure their supplements are safe and labeled accurately. The FDA requires that these non-pharmaceuticals contain a disclaimer that says, “This supplement is not intended to diagnose, treat, cure or prevent any disease.” Health Canada licenses “veterinary health supplements” after reviewing safety, efficacy, and manufacturing information provided by the manufacturer. These supplements are not tested by Health Canada.
Your veterinarian is the best source of information about the safety of non-drug health supplements in pets. Just because a supplement is natural does not mean it is safe. All medicines and medicinal plants are potentially toxic if used inappropriately or given at high doses. Supplements can also have side effects, like pharmaceuticals. Few supplements and herbs have been subjected to rigorous scientific trials to determine their efficacy.
Although the information in this handout may be helpful, it also may be incomplete and may not represent the full range of effects the supplement could have on your pet.
How do I give my pet melatonin?
- Melatonin is given orally (by mouth) and comes in various forms, including capsule, tablet, or liquid.
- Oral doses may be given with or without food.
- If vomiting occurs when dosed on an empty stomach, give future doses with food or a treat.
- Follow your veterinarian’s directions and use supplements according to their label.
- Ideally, give this supplement at the same time daily.
- Ensure access to fresh, clean drinking water.
- Wash your hands after handling.
- Do not handle if you have a known sensitivity to this supplement.
- If you have difficulty getting your pet to take the supplement, ask your veterinarian or pharmacist for tips to reduce the stress of medication time for both you and your pet.
This fast-acting supplement should take effect in 1–2 hours and improvements in clinical signs should follow.
What if I miss giving my pet the supplement?
If you miss a dose, give it as soon as you remember. However, if it is almost time for the next scheduled dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once or give extra doses.
Are there any potential side effects?
Melatonin may cause the following side effects:
- Sleepiness
- Weight gain
- Changes in fertility
In humans, altered sleep patterns, sleepiness, itchiness, low body temperature, and headache have been reported. The significance of these side effects in animals is unknown.
Sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.
Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting supplement should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
Are there any risk factors for this supplement?
DO NOT USE melatonin in:
- Pets that are allergic to it
USE WITH CAUTION in:
- Pets that are pregnant, nursing, or used for breeding
- Pets with severe liver disease
- Pets that have not reached sexual maturity (young pets)
Are there any drug interactions I should be aware of?
Several medications should be used with caution when given with melatonin, including:
- Amlodipine
- Benzodiazepines
- Cimetidine
- Ciprofloxacin
- Estrogens
- Fluvoxamine
- Mexiletine
- Propofol
- Succinylcholine
- Warfarin
Be sure to tell your veterinarian about any medications (including vitamins, supplements or herbal therapies) that your pet is taking before starting any treatment.
Is any monitoring needed with this supplement?
- At home, monitor for abnormal changes. If any occur, discontinue the supplement and contact your veterinarian.
- Your veterinarian will let you know when they want to reassess your pet to ensure the supplement is working and not causing side effects.
How do I store melatonin?
- Store oral supplements in a cool dry area in tightly sealed containers to prevent accidental ingestion.
- Keep at room temperature and protect from light.
- Keep out of reach of children and pets
- There are many formulations and manufacturers of melatonin, so always follow the specific storage instructions on the product label.
What should I do in case of emergency?
- If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.
- Be prepared to provide information about the product and your pet’s weight and symptoms.
- Report any adverse effects to the FDA or Health Canada.
