Myopathies are not an unusual complication of drug therapy. The major symptoms in drug-induced myopathies are proximal muscle weakness, increased muscle enzyme levels, electromyographic changes and histological lesions. Some drug-induced myopathies are associated with neuropathy. Drug-induced myopathies can be classified according to the presence or absence of muscular pain and associated neuropathy. Among painless myopathies, we can distinguish myopathies without neuropathy (corticosteroids), myopathies with neuropathy (colchicine, chloroquine and hydroxychloroquine) and myasthenic syndromes (D-penicillamine, antibiotics, beta-blockers). Among painful myopathies, the classification is similar: painful myopathies may or may not be associated with neuropathies. Painful myopathies include polymyositis (D-penicillamine, cimetidine, zidovudine) and other myopathies without polymyositis (clofibrate, statines, cyclosporin). Among the painful neuromyopathies, eosinophilia-myalgia syndrome is a recently described disorder associated with the use of L-tryptophan. Combinations of drugs (for example, a fibrate and a statine or cyclosporin and colchicine) can induce severe myopathies. If such drugs are used together a vigorous surveillance to detect any sign of myopathy is warranted. Instead of classifying drug-induced myopathies according to clinical features, a histological classification can be proposed. Many drugs can induce vacuolar myopathy (colchicine, chloroquine, amiodarone, cyclosporin, drugs causing hypokalaemia and lipid-lowering agents), some others cause a mitochondrial myopathy (zidovudine) or a necrotizing myopathy as seen with vincristine. Overall, several criteria for reporting drug-induced myopathy can be recommended: lack of pre-existent muscular symptoms, a free period between the beginning of the treatment and the appearance of symptoms, lack of another cause accounting for the myopathy, and complete or incomplete resolution after withdrawal of the treatment. Rechallenge of the treatment is not advisable because of the risk of a serious relapse. The exact mechanisms by which drugs cause myopathies are unknown. Some cases may be due to metabolic changes, whereas others may be immune mediated. Nevertheless, the aspect these conditions have in common is the regression of the myopathy with the discontinuation of the drug.

These medications and prevalence rates for drug-induced arthralgia are as follows:

• Risedronate (Actonel®, Warner Chilcott) 11.5 to 32.8 percent
• Fluticasone (Flovent®, GlaxoSmithKline) 1 to 19 percent
• Conjugated estrogen (Premarin®, Pfizer) 7 to 14 percent
• Rosuvastatin (Crestor®, AstraZeneca) 10.1 percent
• Venlafaxine (Effexor XR®, Pfizer) 1 to 10 percent
• Clopidogrel bisulfate (Plavix®, Bristol-Myers Squibb/Sanofi Aventis) 2.5 to 6.3 percent
• Clonidine (6 percent)
• Pregabalin (Lyrica®, Pfizer) 3 to 6 percent
• Carvedilol (1 to 6 percent)
• Meloxicam (0.5 to 5.3 percent)
• Atorvastatin calcium (Lipitor®, Pfizer) 5.1 percent
• Olanzapine (Zyprexa®, Eli Lilly) 5 percent
• Tramadol (1 to 5 percent)
• Lovastatin (0.5 to 5 percent)

Chemotherapy Drugs:

Many doctors who prescribe chemotherapy are well aware that these drugs can cause  nerve damage in the form of peripheral neuropathy. In fact, the onset of peripheral neuropathy can be the primary limiting factor for the amount and duration of the chemotherapy. Chemotherapy can be life-saving, but a painful neuropathy is not easy to live with. The best thing to do is prevent the neuropathy from occurring in the first place by taking Acetyl-L-Carnitine (1000 mg three times daily) which can protect your nerves while using these toxic drugs. Once you have a painful neuropathy, the nerve pain is treated with a variety of different drugs which can have their own set of unwanted side effects.

Chemotherapy Drugs:

Thousands of people take medications to lower cholesterol levels. A portion of these people will also live a life with chronic pain as a result of these medications. Muscle pain and weakness is well known to be a resulting side-effect from cholesterol-lowering drugs, but can easily be mistaken for other things like fibromyalgia without anyone realizing that a drug is causing the pain. If you have recently begun using one of these medications in the past year or two and have suddenly started to feel pain, talk with your doctor about the possibility of these medications being the root cause of your pain.

Opioids (hydrocodone, hydromorphone, oxycodone, morphine):

The drugs used to treat pain can also cause pain. If you have been using opioid drugs for years and the pain keeps getting worse and worse, this vicious pain cycle could be a result of opioid-induced hyperalgesia. Because the opioids turn your natural pain relieving system off, your body is left without enough chemicals in the system as the drug wears off every four to six hours. This cycle causes a frequent roller coaster of up's and down's that sensitizes the nervous system to the point that you feel more pain. Not only do you feel more pain, you feel anxious, restless and have trouble sleeping. If this sounds familiar, then it is time to find an exit strategy off the opioid roller-coaster that you are on