Hydralazine

Hydralazine is a vasodilator that opens up a dog’s blood vessels. It’s used to treat high blood pressure and help manage congestive heart failure. 

Hydralazine for dogs can be used on its own or along with other medications, and it can be given orally or via an injection. If your vet has prescribed hydralazine for your dog, keep reading to find out about the drug’s recommended dosage amount, efficacy, safety, and potential side effects.

Dosage

Hydralazine is available as a tablet, a compounded liquid, and an injection in a veterinary setting. The effective dosage range of hydralazine for dogs is between 0.5 and 3 mg/kg, given orally twice a day.

However, the dosage amount varies based on the condition and how your dog responds to the drug. The dose may also be lower when hydralazine is used in conjunction with other medications that dilate the arteries.

Give hydralazine with food and according to your vet’s instructions. If your dog doesn’t respond well to hydralazine, your vet can adjust the dosage.

Efficacy

Hydralazine is an arteriolar vasodilator that relaxes the smooth muscle of arteries. By widening the blood vessels, it reduces pressure and ensures the easier flow of blood around the body. The main use of hydralazine is to treat hypertension (high blood pressure) in dogs, but it can also be used to help treat congestive heart failure. 

The medication has been shown to produce vasodilation in the coronary, skeletal muscle (quadriceps), splanchnic, and renal circulations in normal dogs. The increase in coronary blood flow was a result of increased cardiac oxygen consumption and narrowed arteriovenous oxygen difference across the heart.

Hydralazine can also treat severe cough in dogs with mitral regurgitation, and potentially reduce pulmonary hypertension in heart failure due to heartworm disease or other causes.

Side effects

Hydralazine for dogs can cause the following side effects:

• Reduced appetite

• Vomiting

• Diarrhea

• Weakness

• Lethargy

• Low blood pressure (hypotension)

• Water retention

• Collapse

• Conjunctivitis

• Constipation

• Allergic reaction 

If your pet experiences any side effects of hydralazine, consult your veterinarian for advice. Depending on your dog’s response to the medication, your vet may adjust the dosage amount or recommend a different medication.

Considerations

Just like any other medication, hydralazine may interact with other drugs your pet is taking. It also may not be suitable for dogs with health issues or who are pregnant, so your veterinarian will need to examine your dog and know their full medical history before prescribing hydralazine.

Drug interactions

Hydralazine for dogs may interact with the following drugs:

• ACE inhibitors

• Beta-blockers (such as propranolol)

• Diazoxide

• Diuretics (such as furosemide)

• Monoamine oxidase inhibitors

• Sympathomimetics

Other drugs may interact with hydralazine, so make sure your veterinarian is aware of all medications your pet is currently taking.

Allergic reactions and sensitivity

Do not give hydralazine to dogs whose blood pressure is already too low. Use caution when giving this medication to dogs with kidney disease, liver disease, or autoimmune diseases, and to dogs with certain heart problems.

Finally, do not give hydralazine for dogs to pets with a known hypersensitivity to this medication.

Frequently asked questions

Does my pet need to get a prescription to take hydralazine?

Yes, this medication is only available with a prescription from your veterinarian. 

How are hydralazine tablets stored?

Store hydralazine tablets at room temperature in a sealed container out of direct sunlight and reach of children.

What should I do if my dog has an adverse reaction to this medication?

If your dog has an adverse reaction to hydralazine or you suspect an overdose, seek emergency veterinary medical attention for your pet immediately.

What if I forget to give my dog a dose of hydralazine?

You can give the missed dose as soon as you realize. However, if it’s close to the time the next scheduled dose is due, skip the missed dose and give the next dose of medication at the scheduled time. Never double up on doses or give extra doses.