Diabetes mellitus is a common endocrine disease in cats similar to type 2 diabetes in humans. Risk factors for cats are being overweight and inactive. Eating a high carbohydrate diet can also contribute. These things lead to too much blood sugar, which, over time, leads to insulin resistance. This is different than type 1 diabetes, where the pancreas isn’t producing insulin. The clinical signs of diabetes in cats are the same as in people: increased drinking and urination, hunger, and unexpected weight loss.
Until recently, the most effective way to treat diabetes in cats was twice-daily insulin injections. Insulin works by helping glucose move from the bloodstream into cells in the body. There was always the risk of giving too much insulin, which could lead to low blood sugar (hypoglycemia) and possibly death. Additionally, owners didn’t like poking their cats twice a day, were worried about missing a dose, and had concerns about taking a vacation and having a pet sitter give injections. Even though the needle is small, cats didn’t like being poked twice a day either.
Approximately 10 years ago, a new class of drugs was discovered to treat type 2 diabetes in humans. Common brands of these sodium-glucose cotransporter 2 (SGLT2) inhibitors include canagliflozin, dapagliflozin, and empagliflozin. After many years of research, two are now available and effective for cats. They are in the same flozin class, but FDA-approved for use in cats only: bexagliflozin (Bexacat) and velagliflozin (Senvelgo). Both medications are given orally—one is a pill (Bexacat) and the other a liquid suspension (Senvelgo)—making them potentially easier to give than insulin. They also only need to be given once a day.
The medications work very differently than insulin. The SGLT2 protein is responsible for the reabsorption of glucose in the kidney. By inhibiting this protein, the kidneys reabsorb less glucose and excrete more glucose in the urine, thus lowering the amount of glucose in the bloodstream. In type 2 diabetics, the pancreas is still producing insulin, but the body doesn’t respond as well. By lowering blood sugar, the cells start responding better to insulin, making the diabetes better controlled.
The important note is that a cat (or human) has to be producing their own insulin for these medications to be used safely. Just decreasing the glucose in the bloodstream of a diabetic cat isn’t going to control the disease. Insulin is needed to move glucose into the cells so the body can function. Remember, in type 2 diabetes, there’s insulin produced, but because of the high amount of glucose in the bloodstream, the cells are resistant to the effects of insulin. By decreasing the glucose in the bloodstream, the cells become more responsive to insulin.
What if you give an SGLT2 inhibitor to a cat who isn’t producing any insulin? Their diabetes will progress and their body will break down fat, leading to ketoacidosis (DKA), which can be fatal if not treated quickly. Clinical signs of DKA are glucose and ketones in the urine, high blood glucose, and a sick kitty. But DKA in a cat taking an SGLT2 inhibitor has euglycemic DKA. Their blood glucose is pretty normal. While there will be a lot of glucose in the urine, we expect that because that’s what the medication does.
Insulin administration is critical in treating DKA, so how do we figure out if they have DKA? When we start cats on insulin injections, we monitor their response and adjust the dose based on blood glucose levels. We know a cat receiving this new medication will have pretty normal glucose levels, so monitoring that isn’t useful. Instead of blood glucose levels, we need to measure ketones.
A cat with DKA will have ketones in their urine. It isn’t a very sensitive test, so we need to monitor ketones in the bloodstream. If DKA is going to happen, it usually happens within the first two weeks of treatment. This is something owners can learn to do with a fairly inexpensive monitor, or their veterinarian can do rechecks the first few weeks the cat is on the new medication as well as periodically after that. If the cat’s ketone levels increase, then we know they aren’t producing insulin and have to switch treatment.
A cat can go into diabetic remission with either insulin or SGLT2 inhibitors. If they’re getting insulin and go into remission, we see periods of low blood sugar during routine monitoring. But with the SGLT2 inhibitors, we don’t see these swings in glucose level. About the only way to determine remission is to stop the medication and see what happens, but it isn’t necessary since there isn’t a problem for a cat in remission to continue taking the medications. An SGLT1 molecule is also responsible for about 10 percent of glucose resorption. When SGLT2 is inhibited, the amount of glucose the SGLT1 molecule absorbs increases, preventing the cat from developing hypoglycemia.
Besides DKA, the main side effects from these medications are gastrointestinal related, diarrhea and vomiting, and are usually self-limiting.
Currently, these medications are not recommended for diabetic cats already receiving insulin in case the pancreas has stopped producing its own insulin. This may change in the future, so if you have a diabetic cat you’d like to try on these medications, consult with your veterinarian. Because diabetic dogs are almost always not producing insulin, these drugs cannot be used with them.
I still don’t like informing owners their cat has diabetes, but at least there are more options for potentially making it easier to treat. If you’re concerned about your cat’s health, please remember that your veterinarian is there to help.
