Achilles tendonitis is common in middle-aged runners and elite and amateur sportspeople. The most common cause is too much load on the tendon. However, obesity, diabetes, and high cholesterol increase the risk. Moreover, some antibiotics can trigger tendon damage, while others can be helpful. So, are antibiotics and Achilles tendons harmful or helpful? 

Antibiotics and Achilles tendons: which are harmful?

Since the 1980s, doctors have noticed a link between people taking antibiotics and Achilles tendonitis and rupture. The first antibiotic linked to tendonitis is the group known as fluoroquinolones. Some of the common antibiotic names in this group include ciprofloxacin and levofloxacin. Other antibiotics known to increase the risk of tendonitis include clindamycin or azithromycin. Since the first reports many years ago, there have been over 100 cases reported in the medical community.

Why do people take these potentially harmful antibiotics? 

These antibiotics treat severe lung, bone, and kidney infections. However, in some cases, these powerful antibiotics have also been prescribed for relatively mild illnesses, such as bronchitis. Recently, there has been an effort to make people aware of this possible link between antibiotics and tendonitis.

Antibiotics and Achilles tendons: why do they cause tendonitis?

We are still determining the answer. However, we think certain antibiotics cause inflammation, leading to a build-up of potent toxins. These toxins directly damage the tendon, causing tendonitis and rupture. Again, however, we are still determining the exact reason and need to do more research into the link. We also know that tendon damage is more significant in people with a history of tendonitis. Moreover, other factors that increase the risk of tendon damage with fluoroquinolone use include the elderly, chronic diseases such as diabetes and the recent use of cortisone tablets or injections.

Also, recent research suggests that certain fluoroquinolones increase the risk of tendonitis and tendon rupture.  One study found that ofloxacin and norfloxacin had the most significant risk of tendon rupture, while another found that levofloxacin was potentially the most harmful.

Antibiotics and Achilles tendon rupture

Generally, the same antibiotics that cause tendonitis increase the risk of complete rupture.

How do you know whether you have antibiotic-induced tendonitis?

Knowing whether antibiotics are causing tendon damage can be challenging. Often, people report sudden pain and swelling in the tendon. Sometimes, pain starts within a few hours of taking the antibiotics. In other cases, a reaction can occur six months after stopping antibiotics. Overall, doctors should be more aware of these reactions. In addition, we should only use these types of antibiotics for serious hospital infections.

What do you do if you think you’ve developed a reaction?

Firstly, you must stop the antibiotics and see your doctor immediately. After that, you may need to change to another antibiotic.

Secondly, diagnostic ultrasound helps confirm the state of inflammation in the tendon. Sometimes, blood tests help with ruling out other causes.

Unfortunately, the treatment of antibiotic tendonitis is not easy. We know that recovery from tendon damage takes longer to heal. Initially, it would be best if you rested the tendon to allow the tendon to heal. A heel raise in your shoes can help. A walking boot may be needed for several weeks in moderate to severe cases. Once the severe pain settles, we suggest a slow strengthening program directed by a physiotherapist. In some cases, walking and calf exercises in a pool might help. Overall, the recovery is slow and can take many months.

boot for calcaneal stress fracture

What other treatments are available? 

Sometimes, we consider options to reduce pain and help with physiotherapy in people who struggle.

GTN patches are helpful. These patches contain a substance called nitric oxide that helps heal collagen. However, it would help if you spoke to your doctor about side effects and how to use the patches correctly. Generally, we use patches for 2-3 months, depending on symptom severity.

Other options, such as shockwave therapy, injections, and surgery, are generally not recommended for antibiotic tendon damage. Finally, cortisone tablets or injections should be avoided due to the risk of tendon rupture.

Antibiotics and Achilles tendons: Which are helpful?   

One type of antibiotic, doxycycline, lowers the levels of an enzyme in the body called MMP. Lowering this enzyme reduces inflammation in tendonitis. This type of antibiotic could help with pain from acute tendonitis. Some of us use this antibiotic for cases of acute tendon pain.

Other commonly asked questions about antibiotics and Achilles tendonitis:

Why does recovery take so long after antibiotic-induced tendonitis?

We suspect certain antibiotics trigger necrosis of the collagen fibres, leading to severe tendonitis and, in some cases, tendon rupture. Generally, recovery is much longer than overload-induced tendonitis, averaging 6-12 months.

Can fluoroquinolones cause other musculoskeletal problems in addition to tendonitis?

According to the Medicines and Healthcare Products Regulatory Agency (MHRA) in the UK, fluoroquinolones can cause other symptoms such as joint pain or swelling in shoulders, arms, or legs, abnormal pain or sensations such as persistent pins and needles, tingling, tickling, numbness, or burning, weakness or difficulty walking, changes in vision, taste, smell, or hearing. If you develop any of these symptoms, you should stop the medication immediately and seek medical attention. MHRA suggests restricting fluoroquinolones to treat severe infections only where other antibiotics are ineffective or inappropriate. 

Do certain types of fluoroquinolones increase the risk of tendonitis or tendon rupture? 

Yes, we think so. 

One study found that ofloxacin and norfloxacin had the most significant risk of tendon rupture, while another found that levofloxacin was potentially the most harmful.

Final word from Sportdoctorlondon about antibiotic tendon damage

Antibiotic-induced tendonitis can be a devastating injury. You should see your doctor immediately if you think you’ve developed a reaction. Healing can take months to years and requires an expert to guide recovery. Generally, people should avoid these antibiotics unless they have severe hospital infections. 

Other tendon information:

Dr Masci is a specialist sports doctor in London. 

He specialises in muscle, tendon and joint injuries.