Tenofovir disoproxil fumarate

HIV Treatment

Tenofovir disoproxil fumarate is prescribed to treat HIV-1 infection in adults and children. It is used in combination with other antiretroviral drugs to help lower the amount of HIV in the blood. By reducing the viral load, the medication helps the immune system work better and lowers the chance of developing infections or other HIV-related illnesses.

Chronic Hepatitis B Treatment

This medication is used to treat long-term (chronic) hepatitis B infection. It works by interfering with the virus's ability to multiply, which can reduce the amount of hepatitis B virus in the body. This treatment may help prevent serious liver problems, such as liver failure or liver cancer, although it does not eliminate the virus entirely.

HIV Prevention

Tenofovir disoproxil fumarate is also used to reduce the risk of getting HIV-1 infection in individuals who are at high risk. This use is part of a strategy called pre-exposure prophylaxis (PrEP). For prevention, it is typically used alongside other medications and safe sex practices.

Mechanism of Action

Tenofovir disoproxil fumarate belongs to a class of drugs known as nucleoside reverse transcriptase inhibitors (NRTIs). It works by blocking an enzyme called reverse transcriptase, which is essential for certain viruses to replicate and spread.

Managing HIV

In people with HIV, the medication prevents the virus from making copies of itself. By reducing the amount of HIV in the blood, also known as the viral load, it helps the immune system function more effectively and lowers the risk of developing complications related to the infection.

Managing Hepatitis B

For chronic hepatitis B, the drug works by interfering with the virus's ability to multiply and infect new liver cells. This helps to decrease the amount of the hepatitis B virus in the body over time, which may reduce the risk of liver damage.

It is important to note that while this medication helps control these infections, it is not a cure for HIV or hepatitis B. It also does not prevent the spread of these viruses to others through sexual contact or exposure to blood.

Common Side Effects

Many people taking tenofovir disoproxil fumarate experience mild side effects. These may include:

• Nausea, vomiting, or gas
• Diarrhea
• Headache
• Dizziness
• Depression or trouble sleeping
• Back pain
• Itching or rash
• Weight loss

Serious Side Effects

While less common, some side effects require immediate medical attention. Contact a healthcare provider if you experience any of the following:

Kidney and Bone Problems

• Kidney issues: Signs may include decreased urination or swelling in the legs and feet.
• Bone thinning: This medication may lead to a loss of bone mineral density, increasing the risk of bone pain or fractures.

Lactic Acidosis and Liver Issues

• Lactic acidosis: This is a buildup of acid in the blood. Symptoms include unusual muscle pain, stomach pain, extreme tiredness, fast breathing, or feeling cold in the arms and legs.
• Liver problems: Signs include yellowing of the skin or eyes (jaundice), dark urine, light-colored stools, or loss of appetite.

Immune System Changes

Some patients may develop immune reconstitution syndrome. This occurs when the immune system becomes more active and begins to fight hidden infections, which may cause old symptoms to return or new symptoms to appear shortly after starting the medication.

Hepatitis B Warning

Individuals with hepatitis B virus (HBV) infection who stop taking tenofovir disoproxil fumarate may experience a severe worsening of their condition. Liver function is typically monitored closely for several months after the medication is discontinued. It is important not to stop treatment without consulting a healthcare provider.

Lactic Acidosis and Liver Issues

The use of this medication has been associated with lactic acidosis, a serious condition where lactic acid builds up in the blood. It may also cause severe liver enlargement (hepatomegaly) or fatty liver (steatosis). These conditions can be life-threatening. Symptoms that may indicate these issues include:

• Unusual muscle pain or weakness
• Stomach pain with nausea and vomiting
• Feeling cold, especially in the arms and legs
• Dizziness or lightheadedness
• Fast or irregular heartbeat

Kidney Impairment

Tenofovir disoproxil fumarate can cause kidney damage, including acute kidney failure and Fanconi syndrome. Healthcare providers often perform blood and urine tests to monitor kidney health and phosphorus levels before and during treatment. The risk may increase when used with other drugs that can also affect the kidneys.

Bone Density Loss

Decreases in bone mineral density have been observed in patients taking this medication. This can lead to an increased risk of fractures or bone softening (osteomalacia). Bone density monitoring may be recommended for individuals with a history of bone issues or those at high risk for bone loss.

Immune System Changes

In some patients with HIV, the immune system may trigger an inflammatory response to previous or hidden infections, such as pneumonia or tuberculosis, shortly after starting treatment. This is known as immune reconstitution syndrome and may require further medical evaluation.

Pregnancy

Research involving pregnant individuals has generally not shown that tenofovir disoproxil fumarate causes an increased risk of birth defects or other pregnancy complications. Healthcare providers often prescribe this medication during pregnancy because controlling HIV or Hepatitis B is essential for the health of the parent and to prevent the virus from being passed to the infant.

If you are pregnant or planning to become pregnant, your healthcare provider may discuss enrolling you in a pregnancy registry. These registries collect information to monitor the safety of antiviral medications and track the health outcomes of both the parent and the baby.

Breastfeeding

Tenofovir disoproxil fumarate can pass into breast milk in small amounts. The recommendations for breastfeeding depend on the condition being treated and the guidance of a healthcare professional:

• HIV: Health organizations generally recommend that individuals with HIV do not breastfeed. This is because the virus can be transmitted to the baby through breast milk, even if the parent is taking antiviral medication.
• Hepatitis B: The risks and benefits of breastfeeding while taking this medication for Hepatitis B should be discussed with a doctor to determine the safest approach for the infant.

Available Forms

Tenofovir disoproxil fumarate is provided in the following oral formulations:

• Oral Tablets: These are intended to be swallowed whole.
• Oral Powder: This form is available for patients who have difficulty swallowing tablets. It is typically mixed with soft food before administration.

FDA Approval and Indications

Tenofovir disoproxil fumarate is approved by the U.S. Food and Drug Administration (FDA) for the treatment of human immunodeficiency virus (HIV-1) infection in adults and pediatric patients 2 years of age and older who weigh at least 10 kg. For HIV treatment, it must be used in combination with other antiretroviral medications.

The medication is also FDA-approved to treat chronic hepatitis B virus (HBV) infection in adults and pediatric patients 2 years of age and older who weigh at least 10 kg.

Boxed Warnings

The FDA has issued a boxed warning for tenofovir disoproxil fumarate due to the following serious risks:

• Post-treatment Exacerbation of Hepatitis B: Severe, acute flare-ups of hepatitis B have been reported in patients who stop taking this medication. Liver function should be monitored closely for several months in patients who discontinue treatment.
• Lactic Acidosis and Severe Liver Problems: There is a risk of lactic acidosis (a dangerous buildup of acid in the blood) and severe liver enlargement with fatty deposits (steatosis), which can be life-threatening.

Safety and Monitoring

Tenofovir disoproxil fumarate is not a cure for HIV or hepatitis B. Because the medication is primarily cleared by the kidneys, the FDA recommends that healthcare providers assess kidney function (creatinine clearance) before starting treatment and monitor it regularly during therapy. It may also cause a decrease in bone mineral density, and bone monitoring may be considered for patients with a history of bone fractures or other risk factors.

Generic Availability

Tenofovir disoproxil fumarate is available as a generic medication and as the brand-name drug Viread. Generic medications are typically less expensive than brand-name versions while providing the same therapeutic benefits.

Factors Influencing Price

Several factors can affect the final price a patient pays for this medication:

• Insurance Coverage: Most prescription drug plans provide coverage for tenofovir disoproxil fumarate, but the out-of-pocket cost will depend on the specific plan's deductible and copayment structure.
• Dosage Form: The medication is available in different forms, including oral tablets and oral powder, which may have different price points.
• Pharmacy Selection: Prices may vary between different retail pharmacies or mail-order services.

Patients are encouraged to check with their insurance provider or pharmacist to determine the exact cost and to inquire about potential financial assistance programs if needed.