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Trazodone HCL
Revised: January 17, 2023
Published: January 04, 2017

(For veterinary information only)

The size of the tablet/medication is NOT an indication of a proper dose. Never administer any drug without your veterinarian's input. Serious side effects or death can occur if you use drugs on your pet without your veterinarian's advice. 

It is our policy not to give dosing information over the internet.

Brand Name:  Oleptro, Desyrel

Available in: 50 mg, 100 mg, 150 mg, 300 mg tablets


Anxiety and depression are unfortunately common human problems with pharmaceutical solutions in abundance. People want to be free from worry and stress without suffering drowsiness, addiction, or any other untoward side effects thus new medications are nearly constantly in development. Many such medications, trazodone included work by increasing serotonin levels in the brain. Increasing serotonin in the brain means less anxiety and a happier attitude. By inhibiting the brain’s system for removing used serotonin, serotonin 2A antagonist/reuptake inhibitors like trazodone cause serotonin to linger, lasting longer. The more serotonin we have in our brains, the less anxiety, obsession, and depression we get. Trazodone is used to treat depression in humans and is used to treat anxiety in dogs and cats.

How this Medication Is Used

Trazodone is typically used to manage short-term canine and feline anxiety issues. It has been useful in helping orthopedic patients stay relaxed during confinement and recovery periods as well as in other situations where anxiety is a problem: travel, visits to the vet, fireworks or thunderstorms, etc. It is frequently combined with other anxiety medications to enhance its effects.

Most pets experience anxiety relief within two hours of administration. This can be variable, however, as can the duration of action, so it is important to test the medication before the anticipated event so as to know what to expect. Often trazodone is given at a lower dose for a couple of days to reduce the potential for upset stomach side effects.

Trazodone can be used long-term (generally given twice a day with or without food) or on an as-needed basis. It can take up to two weeks to achieve maximum anxiety relief when trazodone is used long-term. 

Side Effects

When trazodone use has been studied in dogs, 80 percent of dogs using trazodone experienced no negative side effects. For the dogs that did experience them, the effects most often seen involved aggressive food seeking, sedation, nausea, and diarrhea. Some experts recommend using a lower dose of trazodone for a few days to acclimate the patient and help avoid side effects. The most serious potential side effect of trazodone is serotonin syndrome, which is a reaction that occurs when brain levels of serotonin get too high. Elevated heart rate, tremors/shivering, dilated pupils, difficulty breathing, elevated body temperature, or high blood pressure can all be signs of serotonin syndrome. Cyproheptadine acts by reducing brain serotonin levels and can be used to reverse it. Serotonin syndrome is an unlikely effect of trazodone, but it becomes more likely when trazodone is combined with other serotonin-enhancing drugs, so it is important to be able to recognize it. When combined with medications that lower blood pressure, trazodone use can drop blood pressure further, potentially too low.

Interactions With Other Drugs

As mentioned, the risk of serotonin syndrome is increased when other serotonin-enhancing drugs are used with trazodone. Fluoxetine and clomipramine are examples.  MAO inhibitors such as selegiline and amitraz (a tick control product) can also increase the risk of serotonin syndrome, as can concurrent use with the anti-nausea medication metoclopramide. Concurrent use of trazodone and tramadol can increase the risk of serotonin syndrome.

If trazodone is combined with other medications that list sedation as a potential side effect, the chance of tranquilization/sedation will be increased.

There is a risk of increased bleeding tendency when trazodone is combined with non-steroidal anti-inflammatory drugs (NSAIDs).

Trazodone blood levels are increased when trazodone is combined with phenothiazines, such as acepromazine; macrolide antibiotics, such as erythromycin; or with the “azole” antifungal drugs, such as ketoconazole.

Heart rhythm abnormalities can result when trazodone is combined with cisapride (a GI motility modifier), ondansetron (an anti-nausea medication), or with antibiotics of the quinolone class.

Concerns And Cautions

Trazodone can be given with or without food. Nausea side effects, if they occur, are mitigated by giving trazodone with food.

If a dose is accidentally skipped, do not double up next time. Simply pick up the regimen at the next scheduled dose.

Store trazodone tablets at room temperature, protected from light.

Trazodone should not be used in patients in heart failure, liver failure, or kidney failure.

It is our policy not to give dosing information over the Internet.

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