Canagliflozin, commonly marketed under the brand name Invokana, is a medication prescribed to manage type 2 diabetes mellitus. This drug works by inhibiting SGLT2 receptors in the proximal renal tubules, which decreases renal glucose absorption and increases urinary excretion of glucose. While canagliflozin can be highly effective in controlling blood sugar levels and offers additional benefits such as reducing the risk of cardiovascular events and kidney disease progression, it also carries potential side effects that patients and healthcare providers must carefully monitor. Understanding these side effects, recognizing warning signs early, and implementing preventive strategies are essential for safe and effective use of this medication.

Understanding Canagliflozin and How It Works

Canagliflozin is used together with proper diet and exercise to treat type 2 diabetes, and is also used to lower the risk of heart attack, stroke, or death in patients with type 2 diabetes and heart or blood vessel disease. Additionally, it is used to lower the risk of end stage kidney disease, worsening of kidney function, and hospitalization for heart failure in patients with type 2 diabetes and diabetic kidney disease with a certain amount of protein in the urine.

Sodium-glucose co-transporter 2 (SGLT2) is expressed on the proximal renal tubules and is primarily responsible for the reabsorption of 90% of the glucose filtered by our kidneys. By blocking this transporter, canagliflozin causes excess glucose to be eliminated through urine rather than being reabsorbed into the bloodstream. This unique mechanism of action sets SGLT2 inhibitors apart from other diabetes medications that work by stimulating insulin production or improving insulin sensitivity.

Canagliflozin was approved in 2013 by the Food and Drug Administration (FDA) and is utilized to treat patients who are diagnosed with type 2 diabetes mellitus and other disease states. The medication is typically taken once daily before the first meal of the day and is available in 100 mg and 300 mg tablet strengths.

Common Side Effects of Canagliflozin

The most commonly reported adverse reactions have included female genital mycotic infections, urinary tract infection, and increased urinary frequency. These side effects occur because the medication increases glucose levels in the urine, which can create an environment conducive to bacterial and fungal growth. While these effects are generally manageable, they require attention to prevent complications.

Genital Yeast Infections

Genital mycotic infections are among the most frequently reported side effects of canagliflozin, particularly in women. Canagliflozin can cause serious infections in the penis or vagina. These infections occur because the increased glucose in urine provides an ideal environment for yeast and fungal organisms to thrive. Symptoms may include itching, burning, discharge, odor, and discomfort in the genital area.

Patients with a history of genital mycotic infections were more likely to develop genital mycotic infections on canagliflozin, and female patients who developed genital mycotic infections were more likely to experience recurrence and require treatment with oral or topical antifungal agents and anti-microbial agents. Maintaining good hygiene practices and promptly treating any infections can help minimize this risk.

Urinary Tract Infections

Urinary tract infections (UTIs) are another common side effect associated with canagliflozin use. The increased glucose concentration in urine can promote bacterial growth in the urinary tract. Symptoms of a UTI may include painful urination, increased urinary frequency, urgency, cloudy or foul-smelling urine, and lower abdominal discomfort.

Patients should be vigilant about staying well-hydrated and practicing proper hygiene to reduce the risk of UTIs. If symptoms of a urinary tract infection develop, prompt medical evaluation and treatment are essential to prevent the infection from spreading to the kidneys.

Increased Urination

Because canagliflozin works by causing the kidneys to excrete more glucose through urine, increased urination is an expected effect of the medication. Patients may notice they need to urinate more frequently throughout the day and night. While this is a normal response to the medication's mechanism of action, it can be inconvenient and may contribute to dehydration if fluid intake is not adequate.

Dehydration and Low Blood Pressure

Canagliflozin results in osmotic diuresis, leading to reduced intravascular volume, and concomitant use with diuretics can increase the risk of dehydration and hypotension. Elderly patients are more likely to have unwanted effects such as lightheadedness, dizziness, fainting, or dehydration.

Canagliflozin may cause dizziness, lightheadedness, and fainting when you get up too quickly from a lying position. This orthostatic hypotension occurs because the medication can reduce blood volume through increased urination. Patients should be advised to rise slowly from sitting or lying positions and to maintain adequate hydration throughout the day.

Serious Side Effects and Warnings

While many side effects of canagliflozin are mild and manageable, there are several serious adverse reactions that require immediate medical attention. Understanding these risks is crucial for both patients and healthcare providers.

Diabetic Ketoacidosis

Use of sodium glucose cotransporter 2 (SGLT2) inhibitors in patients with type 1 or type 2 diabetes mellitus significantly increases the risk of life-threatening diabetic ketoacidosis (DKA). Ketoacidosis associated with use of SGLT2 inhibitors may be present without markedly elevated blood glucose concentrations (e.g., less than 250 mg/dL).

Fatal cases of ketoacidosis have been reported in patients with type 2 diabetes mellitus receiving SGLT2 inhibitors in the postmarketing setting. Symptoms of ketoacidosis include nausea, vomiting, abdominal pain, confusion, unusual drowsiness, difficulty breathing, and a fruity odor to the breath. Because ketoacidosis can occur even when blood sugar levels are not extremely high, patients should be educated about these warning signs and instructed to seek immediate medical care if they develop.

If you take canagliflozin and become unwell, you should temporarily stop taking it, check your ketones and blood sugars, and speak to your healthcare team, as taking this medication when you're not very well could increase your risk of developing DKA.

Acute Kidney Injury

From March 2013 to October 2015, the US FDA received 101 confirmable case reports of acute kidney injury with use of canagliflozin or dapagliflozin, with hospitalization necessary in 96 cases, intensive care unit admission in 22 cases, and death in 4 patients. Acute kidney injury can develop suddenly and may be related to dehydration, low blood pressure, or other factors.

Symptoms of kidney problems may include decreased urination, swelling in the legs or feet, fatigue, confusion, nausea, and shortness of breath. In a pooled analysis among patients with moderate renal impairment, the incidence of renal related adverse reactions such as increased serum creatinine, decreased eGFR, renal impairment, or acute renal failure was higher in patients receiving canagliflozin compared with those receiving comparator drug or placebo. Regular monitoring of kidney function through blood tests is essential for patients taking canagliflozin.

Fournier's Gangrene

Reports of necrotizing fasciitis of the perineum (Fournier's gangrene), a rare but serious and life-threatening necrotizing infection requiring urgent surgical intervention, have been identified in postmarketing surveillance in patients with diabetes mellitus receiving SGLT2 inhibitors, including canagliflozin. Cases have been reported in both females and males, with serious outcomes including hospitalization, multiple surgeries, and death.

Get medical help right away if you have burning, itching, odor, discharge, pain, tenderness, redness or swelling of the genital or rectal area, fever. This rare but extremely serious infection requires immediate emergency medical treatment and surgical intervention.

Lower Limb Amputation Risk

This medicine may increase your risk of having leg, toe, or midfoot amputation, and you should check with your doctor right away if you have pain, tenderness, sores or ulcers, or infections on your leg or foot. In the CANVAS trial, amputations per 1000 patients per year in patients receiving canagliflozin were 5.8 compared to 2.8 in the placebo group, and in the CANVAS-R trials, these numbers were 7.5 and 4.2, respectively.

In 2017, the FDA gave canagliflozin a box warning highlighting the increased risk of leg and foot amputations, though as of August 2020, the FDA has removed this box warning. Despite the removal of the boxed warning, patients should remain vigilant about foot care and report any concerning symptoms to their healthcare provider immediately.

Bone Fracture Risk

The FDA issued a drug safety communication for canagliflozin to address risks for bone fracture and decreased bone density, adding information to the Warnings and Precautions section to reflect new information from a placebo study. This medicine may increase the risk of bone fractures, and patients should ask their doctor about ways to keep bones strong to help prevent fractures.

A report on the ongoing cardiovascular outcomes trial for canagliflozin revealed interim findings of new safety concerns including heightened risk of bone fracture that was found to increase with the duration of treatment. Patients with existing risk factors for bone fractures should discuss these concerns with their healthcare provider before starting canagliflozin.

Allergic Reactions

This medicine may cause serious allergic reactions, including anaphylaxis or angioedema, which can be life-threatening and require immediate medical attention. Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

In the pool of eight clinical trials, hypersensitivity-related adverse reactions (including erythema, rash, pruritus, urticaria, and angioedema) occurred in 3.0%, 3.8%, and 4.2% of patients receiving comparator, canagliflozin 100 mg, and canagliflozin 300 mg, respectively. Any signs of an allergic reaction should be treated as a medical emergency.

Signs and Symptoms to Watch For

Recognizing the warning signs of serious side effects early can be lifesaving. Patients taking canagliflozin should be educated about the following symptoms that warrant immediate medical attention.

Symptoms of Ketoacidosis

Diabetic ketoacidosis is a medical emergency that requires immediate treatment. Warning signs include:

  • Nausea and vomiting
  • Abdominal pain or discomfort
  • Unusual fatigue or weakness
  • Confusion or difficulty concentrating
  • Difficulty breathing or shortness of breath
  • Fruity-smelling breath
  • Excessive thirst

It is important to note that ketoacidosis can occur even when blood glucose levels are not extremely elevated, making it crucial to recognize these symptoms regardless of blood sugar readings.

Signs of Serious Infection

Serious genital or urinary tract infections require prompt medical evaluation. Warning signs include:

  • Fever or chills
  • Severe pain or tenderness in the genital or rectal area
  • Significant redness or swelling
  • Unusual discharge or strong odor
  • Feeling generally unwell or fatigued
  • Persistent or worsening symptoms despite initial treatment

Indicators of Dehydration

Dehydration can lead to serious complications if not addressed. Symptoms to watch for include:

  • Excessive thirst
  • Dry mouth and lips
  • Dizziness or lightheadedness, especially when standing
  • Dark-colored urine or decreased urination
  • Fatigue or weakness
  • Rapid heartbeat
  • Confusion or irritability

Foot and Leg Problems

Given the increased risk of lower limb complications, patients should monitor their feet and legs carefully for:

  • New pain or tenderness
  • Sores, ulcers, or wounds that are slow to heal
  • Redness, warmth, or swelling
  • Signs of infection
  • Changes in skin color or temperature
  • Numbness or tingling sensations

Kidney Function Concerns

Symptoms that may indicate kidney problems include:

  • Decreased urination or changes in urine output
  • Swelling in the legs, ankles, or feet
  • Persistent fatigue or weakness
  • Nausea or loss of appetite
  • Difficulty concentrating or confusion
  • Shortness of breath

Comprehensive Preventive Measures

While canagliflozin carries certain risks, many side effects can be prevented or minimized through proper precautions and patient education. Implementing these preventive strategies can help ensure safe and effective use of the medication.

Maintain Adequate Hydration

Drink plenty of liquids while you are taking canagliflozin. Staying well-hydrated is one of the most important preventive measures for patients taking this medication. Adequate fluid intake helps prevent dehydration, reduces the risk of urinary tract infections, and supports kidney function.

Patients should aim to drink water throughout the day, especially during hot weather or when engaging in physical activity. Call your doctor if you are sick with vomiting or diarrhea, or if you are sweating more than usual. During illness or situations that increase fluid loss, extra attention to hydration is essential.

Follow Prescribed Dosage Carefully

Use the medicine exactly as directed. Canagliflozin is usually taken once per day, before the first meal of the day. Taking the medication as prescribed helps optimize its effectiveness while minimizing the risk of side effects. Patients should never adjust their dose without consulting their healthcare provider.

Your doctor may tell you to stop taking canagliflozin at least 3 days before your scheduled surgery if you will not be able to eat or drink normally for a long time, and will tell you when to start taking canagliflozin again after your surgery. Following these instructions is important to prevent complications during surgical procedures.

Regular Medical Monitoring

It is very important that your doctor check your progress at regular visits, especially during the first few weeks that you take this medicine, and blood and urine tests may be needed to check for unwanted effects. Regular follow-up appointments allow healthcare providers to monitor kidney function, assess for side effects, and adjust treatment as needed.

Monitoring should include:

  • Regular blood tests to assess kidney function (creatinine, eGFR)
  • Blood glucose monitoring as directed
  • Blood pressure checks
  • Periodic assessment for signs of infection
  • Evaluation of foot health
  • Review of any new or worsening symptoms

Practice Good Hygiene

To reduce the risk of genital and urinary tract infections, patients should:

  • Maintain good personal hygiene, especially in the genital area
  • Wipe from front to back after using the bathroom
  • Urinate after sexual activity
  • Wear breathable, cotton underwear
  • Avoid tight-fitting clothing
  • Change out of wet clothing or swimsuits promptly
  • Avoid using harsh soaps or douches in the genital area

Comprehensive Foot Care

Given the increased risk of lower limb complications, meticulous foot care is essential:

  • Inspect feet daily for cuts, blisters, redness, or other abnormalities
  • Keep feet clean and dry
  • Moisturize feet to prevent dry, cracked skin (but not between toes)
  • Trim toenails carefully and straight across
  • Wear properly fitting, comfortable shoes
  • Never walk barefoot, even indoors
  • Seek prompt medical attention for any foot injuries or infections
  • Have regular foot examinations by a healthcare provider

Blood Sugar Monitoring

Regular blood glucose monitoring helps ensure the medication is working effectively and allows for early detection of problems. Taking medication(s), making lifestyle changes (e.g., diet, exercise, quitting smoking), and regularly checking your blood sugar may help to manage your diabetes and improve your health.

This medicine may cause hypoglycemia (low blood sugar), which is more common when taken together with other diabetes medicines (eg, insulin, glipizide, or glyburide). Your healthcare team may advise reducing the dose of your sulphonylurea or insulin medicine when you start taking canagliflozin to reduce the risk of hypos.

Lifestyle Modifications

Healthy lifestyle choices complement medication therapy and can help reduce side effect risks:

  • Follow a balanced, diabetes-appropriate diet
  • Engage in regular physical activity as recommended by your healthcare provider
  • Maintain a healthy weight
  • Avoid smoking and limit alcohol consumption
  • Get adequate sleep
  • Manage stress effectively
  • Take steps to support bone health, including adequate calcium and vitamin D intake

Medication Management

Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take, as your doctor may need to change the doses of your medications or monitor you carefully for side effects.

Certain medications can interact with canagliflozin or increase the risk of side effects. Canagliflozin results in osmotic diuresis, and concomitant use with diuretics can increase the risk of dehydration and hypotension, so the dosing of diuretics should be adjusted accordingly. Always inform all healthcare providers that you are taking canagliflozin, including dentists and specialists.

Special Populations and Considerations

Elderly Patients

Patients older than 65 years have a higher incidence of adverse reactions, particularly with the 300 mg daily dosage, with a more prominent increase in incidence noted in patients older than 75 years. Elderly patients may be more susceptible to dehydration, low blood pressure, and kidney problems. Healthcare providers may need to adjust dosing or implement additional monitoring for older adults.

Pregnancy and Breastfeeding

You should not use canagliflozin during the second or third trimester of pregnancy. Canagliflozin may harm the fetus. Women who are pregnant or planning to become pregnant should discuss alternative treatment options with their healthcare provider.

Since human kidney maturation occurs in utero and during the first 2 years of life when lactational exposure may occur, there may be risk to the developing human kidney, and use of canagliflozin is not recommended while breastfeeding. You should not breastfeed while using this medicine.

Patients with Kidney Disease

Canagliflozin dosing and use depend on kidney function. If you have kidney disease you might not be able to take canagliflozin or your doses might need to be reduced - this will depend on the stage of your kidney disease. Patients with severe kidney disease or those on dialysis should not use canagliflozin. Regular monitoring of kidney function is essential for all patients taking this medication.

Patients with Liver Disease

If you have severe liver disease you might not be able to take canagliflozin. Patients with liver problems should discuss the risks and benefits of canagliflozin with their healthcare provider, as alternative treatments may be more appropriate.

When to Seek Immediate Medical Attention

Certain symptoms require urgent medical evaluation. Patients should seek immediate medical care if they experience:

  • Signs of ketoacidosis (nausea, vomiting, abdominal pain, confusion, difficulty breathing)
  • Symptoms of a serious allergic reaction (difficulty breathing, swelling of face or throat, severe rash)
  • Signs of Fournier's gangrene (severe pain, tenderness, redness, or swelling in the genital or rectal area with fever)
  • Symptoms of severe dehydration (extreme dizziness, fainting, very dark urine, no urination)
  • Signs of acute kidney injury (significant decrease in urination, severe swelling, confusion)
  • Chest pain or symptoms of heart attack or stroke
  • Severe or persistent infections that do not improve with treatment
  • Foot wounds or infections that are not healing

Drug Interactions to Be Aware Of

Several medications can interact with canagliflozin, potentially affecting its efficacy or increasing the risk of side effects.

Diuretics

As mentioned earlier, combining canagliflozin with diuretics (water pills) can significantly increase the risk of dehydration and low blood pressure. Patients taking both types of medications require careful monitoring and may need dose adjustments.

Insulin and Insulin Secretagogues

There is a risk of hypoglycemia when combined with insulin or an insulin secretagogue, and therefore, a lower dose of insulin or insulin secretagogue may be required to minimize the risk of hypoglycemia when used in combination with canagliflozin. Patients taking these combinations should monitor blood glucose levels closely and be prepared to treat low blood sugar episodes.

UGT and CYP3A4 Enzyme Inducers

If patients are currently tolerating a 100 mg daily dose of canagliflozin and have an eGFR ≥60 mL/min/1.73 m2, consider increasing the dosage to 300 mg daily if coadministered with UGT enzyme inducers such as rifampin, phenytoin, phenobarbital, or ritonavir, as these medications decrease the efficacy of canagliflozin.

Patient Education and Communication

Effective communication between patients and healthcare providers is essential for safe canagliflozin use. Patients should:

  • Read and understand the medication guide provided with each prescription
  • Ask questions about anything that is unclear
  • Report all side effects, even if they seem minor
  • Keep a symptom diary to track any changes or concerns
  • Attend all scheduled follow-up appointments
  • Inform all healthcare providers about canagliflozin use
  • Never stop taking the medication without consulting their doctor
  • Carry medical identification indicating diabetes and current medications

Canagliflozin controls type 2 diabetes but does not cure it, so continue to take canagliflozin even if you feel well, and do not stop taking canagliflozin without talking to your doctor.

Storage and Handling

Proper storage of canagliflozin helps maintain its effectiveness:

  • Store at room temperature, away from moisture and heat
  • Keep the medication in its original container
  • Store out of reach of children and pets
  • Do not use medication past its expiration date
  • Dispose of unused medication properly according to local guidelines

The Role of Healthcare Providers

Healthcare providers play a crucial role in ensuring safe canagliflozin use through:

  • Careful patient selection and screening for contraindications
  • Comprehensive patient education about risks and benefits
  • Regular monitoring of kidney function, blood pressure, and other parameters
  • Prompt evaluation and management of side effects
  • Coordination of care among multiple providers
  • Adjustment of treatment plans as needed based on patient response
  • Documentation of patient education and monitoring

Benefits Beyond Blood Sugar Control

Despite the potential side effects, canagliflozin offers several important benefits beyond glucose control. Evidence shows that apart from positive effects on glycemic levels, canagliflozin also reduces the risk of heart attacks and heart failures. The medication has been shown to provide cardiovascular and renal protective effects in appropriate patients.

For many patients with type 2 diabetes, especially those with cardiovascular disease or kidney disease, the benefits of canagliflozin may outweigh the risks when the medication is used appropriately with proper monitoring and preventive measures in place.

Conclusion

Canagliflozin is an effective medication for managing type 2 diabetes and reducing the risk of cardiovascular and kidney complications. However, like all medications, it carries potential side effects that range from common and manageable to rare but serious. Understanding these risks, recognizing warning signs early, and implementing comprehensive preventive strategies are essential for safe and effective use.

Patients taking canagliflozin should maintain open communication with their healthcare providers, attend regular follow-up appointments, practice good self-care including adequate hydration and hygiene, and seek prompt medical attention for any concerning symptoms. By working together, patients and healthcare providers can maximize the benefits of canagliflozin while minimizing the risk of adverse effects.

Education is key to successful diabetes management. Patients should take advantage of resources provided by their healthcare team, including medication guides, educational materials, and support services. With proper knowledge, vigilant monitoring, and proactive prevention, most patients can use canagliflozin safely as part of a comprehensive diabetes management plan.

For more information about diabetes management and medications, visit the American Diabetes Association, the National Institute of Diabetes and Digestive and Kidney Diseases, or consult with your healthcare provider. Remember that this information is educational in nature and should not replace personalized medical advice from your healthcare team.