By Rania Gollakner, BS, DVM, MPH

What is calcitriol?

Calcitriol (brand names: Rocaltrol®, Calcijex®) is a form of vitamin D used to treat low blood calcium associated with low parathyroid gland function. It may also be helpful in treating chronic kidney disease, certain cancers such as mast cell tumors, and certain skin diseases.

Its use in cats and dogs to treat low blood calcium is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is calcitriol given?

Calcitriol is given by mouth in the form of a capsule or liquid. It should be given on an empty stomach preferably at bedtime. However, if your pet vomits or acts sick after dosing on an empty stomach, give future doses with food or a treat. Measure liquid forms carefully. Do not give calcium supplements while using this medication. It can also given by injection in the hospital setting.

This medication should take effect within 1 to 2 days; however, effects may not be obvious for several weeks. Effects also may not be noted outwardly and therefore laboratory tests may need to be done to evaluate this medication’s effectiveness.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects are uncommon if the dose is appropriate. Doses that are too high may cause side effects such as increased drinking and urination, and lack of appetite. If the dose is not high enough, signs such as muscle tremors, twitching, facial itching, stiffness, weakness, unsteadiness, or seizures may occur.

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?

Calcitriol should not be used in pets that are allergic to it or those with high blood calcium, vitamin D toxicity, or malabsorption syndrome (cannot adequately absorb nutrients from the gastrointestinal tract). It should be used with extreme caution in pets with high blood phosphorus levels, pregnant or lactating pets, or in pets that are prone to calcium oxalate urinary stones.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with calcitriol: calcium-containing phosphorus binding agents, barbiturates, corticosteroids, digoxin, verapamil, magnesium-containing antacids, phenytoin, primidone, or thiazide diuretics.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Ionized blood calcium levels, blood phosphorus levels, and kidney values may be checked by your veterinarian prior to your pet starting this medication. These levels and values should be monitored after one week of treatment, and then every 2-4 weeks. Blood parathyroid hormone levels should also be monitored. Your veterinarian may monitor your pet to be sure that the medication is working.

How do I store calcitriol?

Store at room temperature between 59°F and 86°F (15°C and 30°C), and protect from light.

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.

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