Myalgia during interferon therapy – does it warrant monitoring muscle enzymes?

In a previous report we commentated the event of myositis during treatment of chronic hepatitis C with pegylated interferon á 2a.[1] The symptoms of myositis are myalgia and proximal muscle weakness, which can often be overlooked by clinicians since myalgia and influenza-like symptoms occur in 33-50% of patients when treated with interferon.[2]

This short report looks at the issue whether routine monitoring of the muscles enzymes, creatine kinase (CK) and lactate dehydrogenase (LD) enables clinicians to detect subclinical myopathy.

Methods

Patients with chronic hepatitis C who were on treatment with pegylated interferon á2a (Pegasys:Hoffmann-LA Roche) or pegylated interferon á 2b (Pegintron Schering Plough, Kenilworth, NJ USA) in combination with ribavirin for 48 weeks were selected and we monitored their muscle enzymes CK and LD at baseline and throughout treatment, i.e. at 4, 8, 16, 24, 32 and 48 weeks. All patients were also clinically examined for proximal muscle weakness at the said intervals. All patient’s included had a history of myalgia requiring the use of acetaminophen in quantities of 1 g or more, with each dose of pegylated interferon, for the relief of myalgia.

Patients with history of lipid-lowering agent, alcohol, or anti-malarial use were excluded. Also any patients with abnormal CK or LD at the start of therapy were not included. Any patients with evidence of hemolysis during the course of treatment were also excluded. We obtained IRB approval from our institution and informed consent from each participant before enrollment in the trial. Data analysis was done using the SPSS Version 16 (Statistical package for social sciences, Chicago, IL, USA)

Results

56 patients were included in the study .The clinical features are shown in Table 1. Creatine kinase and lactate dehydrogenase levels remained within normal range during the entire treatment period in 56 patients included in the study. (Table 2).

Discussion

During the entire 48-week treatment period, we noted that the muscle enzymes remained within normal range, though all patients studied had reported myalgia requiring the use of acetaminophen for symptom relief. None had evidence of proximal muscle weakness on examination. The normal muscle enzyme profile excluded subclinical or biochemical myositis in our patients with myalgia. Reports of interferoninduced myositis are few and sparse in literature.[3,4] We therefore conclude that there is no role for routine prospective monitoring of muscles enzymes while on interferon treatment, despite myalgia being a commonly encountered side effect during treatment.

Reference

1. John A, El Emadi S, Al Kaabi S, Morad N, Derbala M, Yakoub R, et al. Polymyositis during pegylated á interferon ribavirin therapy in chronic hepatitis. Indian J Gastroenterol. 2007;26:147–8.

2. Fried MW, Side effects of therapy of hepatitis C and their management. Hepatology. 2002;36(Suppl 1);S237–44

3. Cirigliano G, Della Rossa A, Tavoni A, Viacava P, Bombardieri S. Polymyositis occuring during alpha interferon treatment for malignant melanoma-a case report. Rheumatol Int. 1999;19:65–7.

4. Dietrich LL, Bridges AJ, Albertini MR. Dermatomyositis after interferon alpha treatment. Med Oncol. 2000;14;64–9.

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