Musculoskeletal Disorders

Musculoskeletal disorders are the leading cause of disability. Drug-induced musculoskeletal disorders can vary greatly from those that are asymptomatic biological abnormalities to severe and even life-threatening conditions.

Symptoms of drug-induced musculoskeletal disorders, such as cramps and aches and pains in the limbs, however, should always be taken seriously because, although often debilitating on their own, they can also be precursors of potentially serious disorders. Myalgia (muscle pain), for instance, can be an early indication of rhabdomyolisis (a potentially fatal disease that destroys skeletal muscle). Another example is pain in the joints after the use of fluoroquinolones, which can lead to tendon rupture.

Some of the musculoskeletal disorders most commonly induced by drugs include:

Muscle disorders

  • Myalgia - characterized by diffuse muscle pain, cramps and/or muscle weakness, and tenerness, drug-induced myalgia can affect the patient's quality of life and decrease compliance with therapy
  • Myositis (inflammatory myalgia) - characterized by muscle weakness
  • Rhabdomyolisis - can be caused by statins (particularly when prescribed along with fibrates), ant-psychotics, neuromuscular blocking agents, and drugs that interfere with potassium levels, such as diuretics
  • Myopathy - when induced by drugs, this serious muscle toxicity presents as muscle pain, tenderness and weakness in the proximal muscles of the arms, although it can be more generalized. It should be considered when serum CPK levels are more than ten times the upper limit of normal
  • Statin myopathy - myopathy induced by HMG-CoA reductase inhibitors can vary from mild aches to severe pain. Usually the CPK level in the blood is raised
  • Eosinophilia-myalgia syndrome - a severe, incapacitating myalgia with raised blood eosinophil (a type of white blood cell) count and arthralgia (see below), cough, rash, dyspnea (difficult breathing), edema (swelling), abnormal liver function, and fever

Bone

  • Osteoporosis - corticosteroids are the most common cause of the drug-induced version of this condition, which is characterized low bone mass and increased bone fragility
  • Osteomalacia - symptoms include bone pain, often in the spine, shoulder girdle, ribcage, and pelvis, usually with muscle weakness and tenderness. Culprits associated with the condition or features of the condition include antiepileptics, aluminium, fumaric acid (Fumaderm), corticosteroids, heparin, methotrexate
  • Osteonecrosis - destruction or death of the bone tissue. Phosphates have been associated with osteonecrosis of the jaw (dead jaw)

Joints

  • Arthralgias (joint pain) and arthropathies (joint disease) - including chondropathies (disease involving cartilage) and arthritis (pain and loss of movement of the joints)
  • Tendon rupture - including achilles tendon rupture induced by fluoroquinolone antibiotics
  • Connective tissue diseases, especially lupus-like syndromes, including TNF-alpha inhibitor-induced lupus
  • Other periarticular disorders, including tendinopathies, enthesopathies and frozen shoulder

Other

    • Retroperitoneal fibrosis - this fibrous tissue proliferation behind the peritoneum (membrane that covers the abdominal cavity) and sometimes around the lungs and heart may improve upon removal of the offending agent. But because symptoms are often non-specific, diagnosis may be delayed, resulting in irreversible damage
    • Scleroderma-like disorder (mixed connective tissue disease) - is associated with bleomycin, penicillamine, INH, silicon breast implants
    • Nephrogenic Fibrosing Dermopathy (NSF/NFD) - a condition that can develop in those with advanced renal failure. It causes thickening and hardening of the skin and has been connected to gadolinium-based contrast agents