Mirtazapine Use in Dogs As an Appetite Stimulant

Your dog normally bounds to his food dish at dinner time, tail wagging and ready to dig in. But when pets are suffering from serious diseases like liver failure or cancer, they may turn up their noses at even the most tempting treats. To ensure your dog gets good nutrition as she goes through treatment, your vet may prescribe an appetite stimulant to help revive an interest in food.

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Mirtazapine Use in Dogs As an Appetite Stimulant
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Mirtazapine for dogs

Mirtazapine, whose brand name is Remeron, was developed as an antidepressant for humans. But in dogs and cats, it is most often used to help coax them to eat.

Mirtazapine stimulates neurotransmitters in the brain that are related to relaxation. At the same time, the drug acts on neuroreceptors in the stomach and intestines and provides anti-nausea relief. Put together, these actions provide an effective dog appetite stimulant.

Mirtazapine treats conditions in which dogs have both a poor appetite and nausea, and also includes diseases of the digestive tract and kidney and liver disease. The drug is also used as a canine appetite stimulant for dogs treated for cancer, particularly ones undergoing chemotherapy. Mirtazapine may also be used to address behavioral problems, from separation anxiety to urinating indoors. Once your dog's appetite returns, mirtazapine is discontinued.

Administering mirtazapine

Mirtazapine is available in tablet form for dogs and cats. A transdermal gel that is absorbed by the skin of the ear is approved for cats only. Mirtazapine tablets are available in 7.5 mg, 15 mg, 30 mg, and 45 mg. Dosage is determined by weight, and dogs generally take 3.75 to 30 milligrams per day.

One type of mirtazapine tablet dissolves in the mouth, but it may contain xylitol, which can be toxic to dogs. Also, when a dog has liver or kidney disease, his body may clear the drug more slowly, and your vet may prescribe a dose 30 percent lower than is normally given to a dog of similar size.

Give your dog mirtazapine at around the same time every day. If a dose is missed, give it as soon as possible, but not if the next dose is almost due. It may take several weeks before mirtazapine takes full effect.

Remeron side effects

The most common reported side effect of mirtazapine is drowsiness caused by its antihistamine properties. Another possible side effect can be skin irritation and redness.

One of the less common Remeron side effects, called serotonin syndrome, occurs if the brain levels of serotonin rise too high. Symptoms of this potentially serious syndrome include shivering and tremors, dilated pupils, increased heart rate, elevated body temperature, high blood pressure, and difficulty breathing. Some dogs will become hyperactive if they are experiencing serotonin syndrome. The drug cyproheptadine can be used as an antidote.

Mirtazapine can cause abnormalities in the bone marrow. While the drug can still be used as an appetite stimulant in dogs with leukemia, low platelets or other blood disorders, they will require more vigilant monitoring. Caution should also be used when administering the drug to pregnant or lactating dogs. Talk to your veterinarian about any side effects that bother your dog or seem severe.

Drug interactions

Drugs that inhibit Monoamine Oxidase-A (MAO-A inhibitors) interact with mirtazapine, increasing the risk of serotonin syndrome. While MAO-A inhibitors are rarely prescribed as a drug for dogs, the active ingredient in some anti-tick and mange products contains amitraz, which is an MAO-A inhibitor. One example is the tick collar Preventic. Mitaban dip used to kill mange mites also contains amitraz.

Serotonin syndrome is also a risk when mirtazapine is taken with selective serotonin reuptake inhibitors (SSRIs), such as Prozac. Another drug interaction that raises the risk is the opioid tramadol.