Tenofovir is a cornerstone medication in the management of HIV and chronic Hepatitis B (HBV) infections, available in two main forms: tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) [1.4.2]. While highly effective, it's not suitable for everyone. A thorough understanding of its contraindications and warnings is essential for patient safety.
Key Groups Who Should Exercise Caution or Avoid Tenofovir
Certain medical conditions can be worsened by tenofovir, and its use is outright contraindicated in some cases [1.2.1].
Patients with Pre-existing Kidney Disease
This is the most significant consideration. Tenofovir is eliminated from the body through the kidneys [1.7.3].
- Absolute Contraindication: Individuals with severe kidney disease or those requiring hemodialysis should not use tenofovir, particularly when it's prescribed for pre-exposure prophylaxis (PrEP) [1.2.1].
- Use with Caution: Patients with any history of kidney disease, including acute renal failure or Fanconi syndrome, should use tenofovir with caution [1.2.1, 1.2.3]. Regular and frequent monitoring of renal function (serum creatinine, phosphorus, urine glucose, and protein) is mandatory for these individuals [1.3.3, 1.7.1]. Dose adjustments are often necessary for those with moderate renal impairment [1.2.3].
Individuals with Bone Disorders
Tenofovir, particularly the TDF formulation, has been linked to decreased bone mineral density (BMD) and an increased risk of fractures [1.2.1, 1.6.1].
- Use with Caution: Individuals with a history of bone fractures, osteoporosis (weak bones), or osteomalacia (soft bones) should be carefully evaluated before starting tenofovir [1.2.1]. The medication can exacerbate these conditions [1.2.3]. In some cases, supplementation with calcium and vitamin D may be considered [1.3.2].
Patients with Liver Disease (Beyond HBV)
While tenofovir treats HBV, its use requires care in the context of liver health.
- Worsening of Hepatitis B: If a patient with HBV stops taking tenofovir, their hepatitis can suddenly flare up and become much worse. Medical supervision and regular liver function tests for several months after discontinuation are critical [1.2.2].
- Cirrhosis and Other Liver Issues: Patients with a history of liver disease like cirrhosis should inform their doctor before starting tenofovir [1.2.5, 1.3.1].
Special Populations
- Pregnancy and Breastfeeding: Tenofovir should be used during pregnancy only when clearly needed, after a discussion of risks and benefits with a doctor [1.2.2, 1.2.5]. While it passes into breast milk in very small amounts, and expert guidelines often permit its use, mothers should consult their healthcare provider. For mothers with HIV in the U.S., guidelines recommend discussing all feeding options [1.2.2, 1.9.2].
- Elderly Patients: Older adults are more likely to have age-related kidney or liver problems, which may necessitate dose adjustments and cautious use of tenofovir [1.2.3].
Critical Drug Interactions
Taking tenofovir with certain other medicines can increase the risk of serious side effects, especially kidney damage.
- Nephrotoxic Drugs: Avoid concurrent or recent use of other drugs that can harm the kidneys. This includes high-dose or multiple nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen, and certain other antiviral medications or aminoglycosides [1.2.1, 1.3.4, 1.3.5].
- Other Antivirals: Do not take tenofovir with adefovir or with other combination medicines that already contain tenofovir [1.2.4].
- P-gp and BCRP Affecting Drugs: Certain drugs, like some seizure medications (phenytoin, carbamazepine) and the herbal supplement St. John's wort, can decrease the concentration of tenofovir alafenamide (TAF), reducing its effectiveness [1.5.4].
Comparison of Tenofovir Formulations: TDF vs. TAF
Understanding the differences between the two main forms of tenofovir is key for risk assessment.
| Feature | Tenofovir Disoproxil Fumarate (TDF) | Tenofovir Alafenamide (TAF) |
|---|---|---|
| Plasma Concentration | Higher plasma levels of tenofovir [1.4.2]. | Lower plasma levels, leading to higher intracellular concentration of the active drug [1.4.2]. |
| Kidney Safety | Associated with a higher risk of renal side effects, including decreased estimated glomerular filtration rate (eGFR) [1.4.2]. | Generally considered to have a better renal safety profile with smaller changes in kidney function markers [1.4.2, 1.4.5]. |
| Bone Safety | Associated with greater decreases in bone mineral density (BMD) at the hip and spine [1.4.2]. | Associated with significantly less reduction in BMD compared to TDF [1.4.2]. |
| Lipid Levels | Has a more favorable effect on blood fat levels [1.4.4]. | Can be associated with less favorable changes in lipid profiles, such as increased total cholesterol [1.4.2]. |
Switching from TDF to TAF may improve markers of renal and bone health, especially in patients with poorer baseline renal function [1.4.2, 1.7.4].
Conclusion
Tenofovir is a vital medication for HIV and HBV, but it is not without risks. The decision to use it must be based on a careful assessment of a patient's pre-existing conditions, particularly their renal and bone health. Individuals with known kidney problems, a history of osteoporosis or fractures, and those taking other kidney-harming drugs are among the key groups for who should not take tenofovir or should use it only with rigorous monitoring. Open communication with a healthcare provider and adherence to prescribed lab testing schedules are paramount to using tenofovir safely and effectively.
For further reading, you can consult guidelines from the U.S. Department of Health and Human Services on HIVinfo.nih.gov [1.10.4].
