What is the incidence of ciprofloxacin (fluoroquinolone antibiotic) induced muscle tendon rupture or tendinitis?

Incidence of Ciprofloxacin-Induced Tendon Rupture and Tendinitis

The absolute risk of Achilles tendon rupture from ciprofloxacin is approximately 1 case per 5,958 patients treated (95% CI, 2,148-23,085), with higher risks in elderly patients and those taking corticosteroids. 1

Risk Stratification by Patient Factors

General Population Risk

• Overall incidence of tendon disorders: 4 per 100,000 prescriptions (likely underreported) 1
• Higher estimates suggest 20 cases per 100,000 prescriptions 1
• Tendinitis: 2.4 per 10,000 patients 1
• Tendon rupture: 1.2 per 10,000 patients 1

High-Risk Groups

1. Age-related risk:

   • Patients >60 years: 1 Achilles tendon rupture per 1,638 patients (95% CI, 351-8,843) 1
   • 4 times higher risk in persons >60 years compared to general population 1

2. Medication interactions:

   • Concomitant corticosteroid use: 1 Achilles tendon rupture per 979 patients (95% CI, 122-9,172) 1
   • Dramatic increase in risk with combined use (odds ratio 43.2,95% CI, 5.5-341.1) 1

3. Timing of onset:

   • Majority of cases (93%) occur within 1 month of starting ciprofloxacin 1
   • Median onset: 6 days (range 1-510 days) 1
   • Average exposure duration before symptoms: 2 weeks (range 2-81 days) 1

Anatomical Distribution and Clinical Presentation

• Achilles tendon most commonly affected 1, 2
• Other affected sites include:
  • Rotator cuff (shoulder)
  • Hand tendons
  • Biceps tendon
  • Patellar tendon
  • Thumb tendons 2

Risk Factors for Tendinopathy

The FDA and clinical guidelines identify several risk factors that increase susceptibility:

1. Major risk factors:

   • Age >60 years 1, 2
   • Corticosteroid use 1, 2
   • Renal failure/hemodialysis 1, 3
   • Organ transplantation 1

2. Additional risk factors:

   • Strenuous physical activity/sports participation 1, 2
   • Magnesium deficiency 1
   • Prior tendon disorders 1, 2
   • Rheumatoid arthritis and other inflammatory conditions 1
   • Diabetes mellitus 1, 4

Molecular Mechanisms

Ciprofloxacin causes tendinopathy through several mechanisms:

1. Inhibition of cell proliferation and G2/M cell cycle arrest in tendon cells 4
2. Inhibition of tenocyte migration by down-regulation of focal adhesion kinase phosphorylation 4
3. Enhanced enzymatic activity of matrix metalloproteinase-2 with degradation of type I collagen 4

Prevention and Management

1. Prevention:

   • Avoid ciprofloxacin in high-risk patients when alternatives exist 5, 2
   • Advise patients to rest at first sign of tendon pain 2
   • Maintain hydration during treatment 5
   • Avoid strenuous physical activity during treatment 5

2. Management of tendinopathy:

   • Immediate discontinuation of ciprofloxacin 2, 4
   • Rest and NSAIDs 4
   • Physical therapy with eccentric strengthening exercises 4
   • Surgical intervention may be required for complete ruptures 4, 3

Clinical Pitfalls to Avoid

1. Misdiagnosis: Tendon pain in patients taking ciprofloxacin should raise immediate suspicion of fluoroquinolone-induced tendinopathy 6

2. Inappropriate management: Do NOT prescribe physical therapy or continued activity when tendinopathy is suspected, as this may lead to complete rupture 6

3. Delayed recognition: Symptoms can occur even after completing the antibiotic course, with cases reported up to several months after therapy 2

4. Underestimation of risk: Despite the relatively low absolute risk, the consequences of tendon rupture can be severe, including permanent disability and need for surgical intervention 1, 3