Dichlorphenamide

What is dichlorphenamide?

Dichlorphenamide is used off label (extra label) to treat glaucoma in dogs, cats and rabbits. It is classified as a carbonic anhydrase inhibitor. This medication also acts to change the pH of the urine to an alkaline state, so it may also be used to treat urinary crystals and stones that form in acidic urine.

In the past, dichlorphenamide was mainly used as a diuretic; however, it is rarely used for the purpose now that more potent and effective diuretic drugs are now available.

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.

How do I give my pet dichlorphenamide?

• Dichlorphenamide is given orally or by injection into the vein (IV) or injection under the skin (SQ).
• This medication may also be compounded into other forms, to provide correct dosages for small dogs and cats.
• The oral form of this medication is given by mouth in the form of a tablet. The injectable form is usually given at the veterinary hospital.
• It 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 the instructions on the product label, in conjunction with your veterinarian’s directions.
• Give this medication at the same time daily.
• For chemotherapy-induced nausea, give this medication 30 minutes before receiving chemotherapy drugs.

This medication should take effect within 1 to 2 hours and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose of dichlorphenamide, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects from dichlorphenamide?

Dichlorphenamide may cause the following side effects:

• Panting
• Lack of appetite
• Vomiting, diarrhea
• Sedation or depression
• Excitement 
• High blood sugar levels (hyperglycemia)
• Changes in electrolytes (low potassium and low sodium)
• Skin rash
• Urinary side effects such as the development of crystals in the urine, increased urination, or difficulty urinating
• Suppression of blood cell production in the bone marrow
• False positive results when testing for urine protein

Drug 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 medication 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 medication?

DO NOT USE dichlorphenamide in:

• Pets with a known hypersensitivity to this medication
• Pets with a significant liver disease
• Pets with kidney insufficiency
• Pets with adrenocortical insufficiency (Addison’s disease)
• Pets with low sodium levels (hyponatremia) or low potassium levels (hypokalemia)
• Pets with metabolic acidosis or other electrolyte imbalances
• Pets with severe lung disease

USE WITH CAUTION in:

• Pets that are sensitive to sulphonamides

Are there any drug interactions I should be aware of?

Certain medications may interact with dichlorphenamide, so be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Several medications should be used with caution when given with dichlorphenamide, including:

• Amantadine
• Aspirin
• Digoxin
• Drugs that affect potassium, such as corticosteroids, corticotropin, other diuretics
• Famotidine
• Insulin (rare interaction with the hypoglycemic effects of insulin)
• Methanamine compounds
• Methotrexate
• Mexiletine
• Phenobarbital
• Pimidone
• Quinidine
• Tricyclic antidepressants

Is any monitoring needed with this medication?

• Baseline blood work is recommended to assess your pet’s general health before starting this medication.
• Periodic blood work is advised to monitor this medication’s effects on the body.
• Intraocular pressure measurements (i.e., tonometry) should be performed at intervals determined by your veterinarian.
• At home, monitor for any side effects such as those noted above. If any side effects occur, discontinue use of the medication and contact your veterinarian.
• Your veterinarian will let you know when they want to reassess your pet to ensure the medication is working and not causing side effects.

How do I store dichlorphenamide?

• Store tablets at room temperature (68°F–77°F or 20°C–25°C), with excursions permitted between 59°F and 86°F (15°C and 30°C).
• Store in an airtight container.
• Protect from light and heat.
• Store compounded forms of this medication according to the label.
• Keep medication out of reach of children and pets.

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.