Varenzin-CA1 for Cats

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.  

What Is Varenzin-CA1 Used for in Cats?

Varenzin-CA1 is the first oral medication made specifically for cats with low red blood cell count (non-regenerative anemia) caused by chronic kidney disease (CKD). 

According to a 2011 study, 30–65% of cats with CKD will develop anemia as their kidney function declines. This happens because damaged kidneys don’t produce enough erythropoietin (EPO), a hormone that tells the body to make red blood cells. Without enough red blood cells, the body can’t carry enough oxygen, leading to symptoms such as:  

• Weakness 

• Lethargy (low energy) 

• Loss of appetite (anorexia) 

• Poor quality of life 

Varenzin-CA1 is available as a flavored oral liquid given once a day at home, making it more convenient than in-hospital injections of human EPO products. 

In pre-approval studies, 50–75% of cats treated with Varenzin-CA1 showed improvement in hematocrit (HCT), which measures the percentage of red blood cells in the blood. 

Is Varenzin-CA1 FDA-Approved? 

Varenzin-CA1 is conditionally approved by the FDA for cats for the control of non-regenerative anemia caused by CKD. 

A conditional approval means that the FDA has allowed the manufacturer to market this medication on a year-by-year basis until stronger evidence of the medication’s effectiveness is presented to the FDA within the first five years before a full approval can be granted. 

Speak with your veterinarian about whether Varenzin-CA1 is right for your cat.  

Varenzin-CA1 Considerations for Cats

Varenzin-CA1 should be used with caution in cats with a history of seizures, cats who may be predisposed to developing blood clots (thromboembolic disease), and cats with known hypersensitivity to it or to any of the inactive ingredients. 

Varenzin-CA1 should not be given to pregnant or nursing cats, or cats intended for breeding. 

At the time of publication, the safe use of Varenzin-CA1 had not been evaluated in cats under 1 year of age. 

Because certain medications and supplements—such as phosphate binders and iron supplements—can interfere with the absorption of Varenzin-CA1, it’s important to discuss all of your cat’s medications, including vitamins, supplements, and any medical conditions, with your veterinarian. 

How Varenzin-CA1 Works in Cats

Varenzin-CA1 works by helping the kidneys produce more EPO, which then stimulates the bone marrow to make more red blood cells. 

Molidustat, the active ingredient in Varenzin-CA1, is a type of medication called a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor. Normally, HIF-PH enzymes help stop the body from making EPO, a hormone that tells the body to make red blood cells. By blocking these enzymes, molidustat allows the body to produce more EPO, which leads to an increase in red blood cells. 

How To Give Varenzin-CA1 to Cats

• Always follow the directions on the drug label or as provided by your veterinarian. 

• Shake the bottle well before use. 

• Use the provided syringe to give the medication directly into your cat’s mouth. 

• Do not take apart or wash the syringe after use. 

• Varenzin-CA1 can be given with or without food. 

• Do not give another dose if your cat vomits after taking any portion of the medication. 

• Administer once daily for up to 28 days in a row.  

• If treatment needs to continue, wait at least seven days before starting another cycle.  

If your cat’s anemia is not improving after three weeks of starting Varenzin-CA1, your vet will re-examine your cat for any other underlying condition that may be contributing to the anemia.  

Missed a Dose? 

Speak with your veterinarian about what to do if you forget to give a dose of Varenzin-CA1. 

Generally, your vet may instruct you to give it when you remember or, if it is almost time for your cat’s next dose, to skip the missed dose and resume your normal dosing schedule.  

Do not give extra or double doses. 

Possible Side Effects of Varenzin-CA1 in Cats

In early safety and effectiveness studies, Varenzin-CA1 was generally well tolerated in cats. However, possible side effects may include: 

• Vomiting 

• Increased blood pressure 

• Mild, temporary increase in potassium levels 

Varenzin-CA1 may cause your cat’s HCT levels to become too high, a condition known as polycythemia. Your vet will regularly monitor your cat’s HCT during treatment to make sure it stays within a safe range. 

In the above series of studies, one cat developed a suspected blood clot (thromboembolism), and two cats had a seizure. 

Human Side Effects 

• This medication is for veterinary use only and is not intended for humans. 

• Do not use pet medications for yourself, and never give human medications to pets. 

• Wash your hands immediately after administering the medication or cleaning up spills. 

• Women who are pregnant or may become pregnant should handle this medication with caution. 

• Avoid direct contact if you are allergic or sensitive to molidustat. 

• Do not eat, drink, or smoke while handling Varenzin-CA1. 

• If accidentally ingested, seek medical help immediately or call Poison Control at 800-222-1222. 

Monitoring Your Pet 

Cats starting treatment with Varenzin-CA1 should have their HCT levels monitored weekly, beginning around day 14 of the 28-day treatment cycle.  

After the required seven-day break that follows this cycle, your vet will continue to check your cat’s red blood cell levels on a regular basis—this may be weekly, every two weeks, or monthly.  

If your cat’s HCT drops below the normal range, your vet may start a new treatment cycle. If the levels become too high, treatment with Varenzin-CA1 will be discontinued.  

Your vet may also recommend additional tests depending on your cat’s specific needs, any medications they’re taking, their stage of CKD, or other medical conditions. 

When To Call Your Vet 

Call your veterinarian if you see any of the following, or if you have additional questions or concerns about the use of Varenzin-CA1: 

• Severe side effects (above) 

• Your cat’s condition worsens or does not improve with treatment 

• You see or suspect an overdose 

Varenzin-CA1 Overdose Concerns in Cats

A single overdose of Varenzin-CA1 is unlikely to cause serious toxicity. Signs of an overdose may include: 

• Vomiting 

• Decreased appetite 

• Lethargy 

If you suspect an overdose, immediately seek emergency veterinary care or contact an animal poison control center. Consultation fees often apply. 

• Pet Poison Helpline 855-764-7661  

• ASPCA Animal Poison Control 888-426-4435  

How To Store Varenzin-CA1 for Cats

Keep these storage tips in mind for Varenzin-CA1: 

• Always checks the product label for storage instructions. 

• Store at room temperature between 68–77 F (20–25 C). Brief temperature exposures between 59–86 F (15–30 C) are permitted. 

• Once opened, the medication stays stable for at least 28 days if stored correctly. 

• Keep both the medication and used syringes out of reach of children and pets.