eMedicine Specialties > Neurology > Neuromuscular Diseases
Dermatomyositis/Polymyositis: Treatment & Medication
Updated: Aug 28, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Medical Care
The goal of therapy is to improve muscle strength to improve function in activities of daily living. Improvement in strength is usually accompanied by a decrease in the serum CK level, a change that must be interpreted with caution because most immunosuppressive therapies decrease levels of serum muscle enzymes without necessarily improving muscle strength.
Consultations
- Consultation with an occupational and rehabilitation therapist may help patients with ambulation by providing necessary equipment.
- A swallowing evaluation for dysphagia is recommended.
- Proper emotional support is also important.
Diet
Advise patients who are receiving steroid therapy to follow a strict low-salt, low-carbohydrate, and high-protein diet to avoid weight gain and hypertension.
Activity
Physical therapy helps to preserve muscle function and prevents disuse atrophy of the weak muscles or joint contractures; therefore, consider it in the initial stage of the disease.
Medication
Of all the treatments that are available, prednisone remains the drug of choice.2 If treatment with steroids is not successful, other lines of treatment are considered, such as intravenous immunoglobulins (IVIG), antineoplastic agents, and antimetabolites.3
Systemic corticosteroids
Corticosteroids act as anti-inflammatory and immunosuppressive agents and are the first-line drug for treating both polymyositis and dermatomyositis.
Prednisone (Deltasone, Orasone, Meticorten)
Objective increase in muscle strength by second or third month of therapy determines efficacy.
Adult
Usual starting dose: 1 mg/kg PO qd; length of treatment and taper individualized to clinical response and normalization of CK; general guideline: treatment for 3-4 wk, then taper slowly over 8-10 wk to 1 mg/kg qod; with continued efficacy and no serious adverse effects, reduce dosage further by 5-10 mg PO q3-4wk to lowest possible dose that controls disease; total should be 1-2 y
Pediatric
Usual starting dose: 1-2 mg/kg/d PO; not to exceed 100 mg/d; individualize taper as in adults; total treatment should be at least 1-2 y
Coadministration with estrogens may decrease clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics
Documented hypersensitivity; viral infection; peptic ulcer disease; hepatic dysfunction; connective tissue infections; fungal or tubercular skin infections
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Abrupt discontinuation of glucocorticoids may cause adrenal crisis; hyperglycemia, edema, hypertension, osteonecrosis, myopathy, peptic ulcer disease, cataracts, glaucoma, hypokalemia, osteoporosis, euphoria, psychosis, growth suppression, and infections may occur with glucocorticoid use; patients should be cautioned on excessive appetite, should be on a low-fat, low-carbohydrate diet; should use supplemental calcium and bisphosphonate
Antineoplastic agents
These drugs inhibit cell growth and proliferation. Cyclophosphamide has shown promising results. The drug may be helpful in a subset of patients with interstitial lung disease. Methotrexate (MTX), an antagonist of folate metabolism, has been used frequently despite disappointing results.
Cyclophosphamide (Cytoxan, Neosar)
Chemically related to nitrogen mustards. As alkylating agent, mechanism of action of active metabolites may involve cross-linking of DNA, which may interfere with growth and proliferation of immune cells, in turn resulting in immunosuppression.
Adult
2-2.5 mg/kg/d PO/IV, usually 50 mg PO tid
Pediatric
Administer as in adults
Allopurinol may increase risk of bleeding or infection and enhance myelosuppressive effects; may potentiate doxorubicin-induced cardiotoxicity; may reduce digoxin serum levels and antimicrobial effects of quinolones; toxicity may increase with chloramphenicol; may increase effect of anticoagulants; coadministration with high doses of phenobarbital may increase leukopenic activity; thiazide diuretics may prolong cyclophosphamide-induced leukopenia; coadministration with succinylcholine may increase neuromuscular blockade by inhibiting cholinesterase activity
Documented hypersensitivity; severely depressed bone marrow function
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Increases risk of neoplasia; regularly examine hematologic profile (particularly neutrophils and platelets) to monitor for hematopoietic suppression; regularly examine urine for RBCs, which may precede hemorrhagic cystitis
Methotrexate (Folex PFS, Rheumatrex)
Unknown mechanism of action in treatment of inflammatory reactions. Ameliorates symptoms of inflammation (eg, pain, swelling, stiffness). May affect immune function, including inhibition of production of proinflammatory cytokines. Adjust dose gradually to attain satisfactory response. Children who do not respond to high-dose prednisone should be treated with MTX immediately.
Adult
7.5 mg/wk PO/SC as single dose qwk; depending on clinical response, increase dose 2.5-5 mg/wk to maximum of 25 mg/wk; may also administer IV
Pediatric
Usually started with single weekly dose of 0.25 mg/kg/wk PO/SC, followed by weekly increase to maximum of 0.6 mg/kg/wk depending on clinical response or toxicity
Concurrent PO aminoglycosides may decrease absorption and blood levels; charcoal lowers levels; coadministration with etretinate may increase hepatotoxicity; folic acid or its derivatives contained in some vitamins may decrease response; probenecid, NSAIDs, salicylates, procarbazine, and sulfonamides, including TMP-SMZ, can increase plasma levels; may decrease phenytoin plasma levels; may increase plasma levels of thiopurines
Documented hypersensitivity; alcoholism; hepatic insufficiency; documented immunodeficiency syndromes; preexisting blood dyscrasias (eg, bone marrow hypoplasia, leukopenia, thrombocytopenia, clinically significant anemia); renal insufficiency
Pregnancy
X - Contraindicated; benefit does not outweigh risk
Precautions
Monitor CBC counts qmo and liver and renal function q1-3mo during therapy (more frequently during initial dosing or dose adjustments or elevated MTX is a risk [eg, in dehydration]); toxic effects on hematologic, renal, GI, pulmonary, and neurologic systems; discontinue if blood counts decrease substantially; fatal reactions reported when administered concurrently with NSAIDs; adverse effects include MTX pneumonitis, stomatitis, GI symptoms, leukopenia, renal toxicity, and hepatotoxicity
Immunoglobulins
These drugs improve the clinical and immunologic aspects of the disease. May decrease autoantibody production and increase solubilization and removal of immune complexes. IVIG has been effective in dermatomyositis.4 Improvement is observed after the first infusion and is evident clearly by the second monthly infusion. If no improvement is observed by second or third dose, treatment is unlikely to be successful.
Danieli et al in an open study found that IVIG as an add-on treatment with mycophenolate mofetil is safe and effective in refractory myositis.5
Immune globulin intravenous (Gammunex, Gammagard, Octagam)
At high doses, promising and safe choice with good benefit. Expensive and may have to be repeated q4-6wk to maintain benefit.
Adult
0.4 g/kg/d IV for 5 d or 1 g/kg/d for 2 d
Pediatric
Not established
Globulin preparation may interfere with immune response to live virus vaccine (MMR) and reduce efficacy (do not administer within 3 mo of vaccination)
Documented hypersensitivity; IgA deficiency
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Check serum IgA levels before therapy (use IgA-depleted product, eg, Gammagard S/D); infusions may increase serum viscosity and thromboembolic events; infusions may increase risk of migraine attacks, aseptic meningitis (10%), urticaria, pruritus, or petechiae (2-30 d after infusion); increases risk of renal tubular necrosis in elderly patients and in patients with diabetes, volume depletion, or preexisting kidney disease; laboratory changes associated with infusions include elevated antiviral or antibacterial antibody titers for 1 mo, 6-fold increase in ESR for 2-3 wk, and apparent hyponatremia
Immunosuppressant agents
The use of a nonsteroidal immunosuppressive drug is determined by the need for a steroid-sparing effect when (1) serious complications have developed with steroid use, (2) repeated relapses have occurred each time an attempt was made to lower a high steroid dosage, (3) prednisone did not improve strength, or (4) the patient has a rapidly progressive disease accompanied by severe weakness and respiratory failure.
Mycophenolate Mofetil (CellCept)
Metabolized in liver; CYP450, prodrug converted to mycophenolic acid. Promising drug for the treatment of dermatomyositis/polymyositis.
Adult
2 g PO bid
Pediatric
Not established
Combination with acyclovir or ganciclovir may increase levels for both drugs due to competition for renal tubular excretion; aluminum and/or magnesium in some antacids and cholestyramine-containing products may decrease absorption, reducing levels (do not coadminister); probenecid may increase levels; salicylates and azathioprine may increase toxicity; may decrease levonorgestrel AUC; may decrease response to live viral vaccine; may increase free fraction levels of theophylline when given in combination
Documented hypersensitivity; Lesch-Nyhan syndrome
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Increases risk of infection (monitor blood count); severe renal impairment (CrCl <25 mL/min) may increase adverse effects due to increased free MPA; caution in active peptic ulcer disease; incidence of malignancies and lymphoma consistent with that of other immunosuppressants (0.9%); constipation, nausea, diarrhea, urinary tract infection, and nasopharyngitis common; interstitial lung disorders, colitis, pancreatitis, intestinal perforation, GI hemorrhage, gastric ulcers, duodenal ulcers, and ileus rare; do not chew, crush, or cut Myfortic tab
Azathioprine (Imuran)
Alternative to corticosteroids. Derivative of 6-mercaptopurine. Dosages of 1.5-2 mg/kg/d PO well tolerated. Adverse effects fewer than those of other immunosuppressive agents.
Adult
Starting dose: 50 mg/d PO; increase gradually as tolerated, monitor blood levels; effective range approximately 2-3 mg/kg
Pediatric
Administer as in adults
Toxicity increases with allopurinol; concurrent ACE inhibitors may induce severe leukopenia; may increase levels of MTX metabolites and decrease effects of anticoagulants, neuromuscular blockers, and cyclosporine
Documented hypersensitivity; low levels of serum thiopurine methyl transferase (TPMT)
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
LFTs; reduce dose if platelet count <150 X 109/L or total neutrophil count <1 X 109/L; monitor blood parameters qwk initially, then each mo as stable dose achieved; total WBC count may be reduced to 4 X 109/L, and lymphocyte count may be reduced to about 7.5 X 109/L; some patients may have flu symptoms
More on Dermatomyositis/Polymyositis |
| Overview: Dermatomyositis/Polymyositis |
| Differential Diagnoses & Workup: Dermatomyositis/Polymyositis |
 Treatment & Medication: Dermatomyositis/Polymyositis |
| Follow-up: Dermatomyositis/Polymyositis |
| Multimedia: Dermatomyositis/Polymyositis |
| References |
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References
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Further Reading
Keywords
dermatomyositis, polymyositis, inflammatory myopathies, primary muscle weakness, endomysial inflammation, elevated levels of serum muscle enzymes, myositis-associated antibodies, MAA, myositis-specific antibodies, MSA, muscle diseases, juvenile dermatomyositis, childhood dermatomyositis, overlap syndrome, polymyositis associated with neoplasia, polymyositis associated with connective tissue disorder, dermatomyositis associated with neoplasia, childhood dermatomyositis with necrotizing vasculitis, childhood myositis with necrotizing vasculitis
