Ankylosing spondylitis and symptom-modifying vs disease-modifying therapy

The main objectives of medical therapy in ankylosing spondylitis (AS) are to relieve pain, stiffness and fatigue and to prevent structural damage. The Assessment in Ankylosing Spondylitis Working Group has proposed different domains with specific instruments to assess the efficacy of therapeutic agents classified as symptom-modifying and disease-controlling antirheumatic drugs.

Non-steroidal antiinflammatory drugs (NSAIDs) are still the first-line treatment in the management of AS, and they are effective in controlling symptoms such as pain and stiffness and maintaining mobility in many patients. A recent randomized trial suggested that the progression of radiological damage occurs less on continuous use of celecoxib compared with on-demand use. If such findings were confirmed by other studies, the therapeutic value of NSAIDs in AS may extend beyond symptom control. However, for each individual patient, the expected advantages of treatment with NSAIDs should be weighted against any possible gastrointestinal and cardiovascular disadvantages.

Disease-modifying antirheumatic drugs (DMARDs) are widely used for second-line therapy in AS, but the evidence for their efficacy is poor. The term ‘DMARD’ has been borrowed from rheumatoid arthritis, and none of the DMARDs have been shown to prevent or significantly decrease the rate of progression of structural damage which is required to be qualified as a disease-controlling antirheumatic drug for AS. Sulphasalazine is the most extensively studied DMARD and studies suggest some degree of clinical benefit confined to peripheral joint involvement, but no evidence of benefit in axial disease. Methotrexate, which is the gold standard DMARD in rheumatoid arthritis, does not seem to have a substantial therapeutic effect in AS on axial or peripheral joint involvement. Leflunomide appears to exert little beneficial effect, if any, even on peripheral joint involvement.

There is also good evidence that local therapy with corticosteroids is effective and may be used in selected patients. Oral corticosteroids may be somewhat effective in relieving the symptoms of AS, but this has not been formally studied. Small studies have reported favourable results with intravenous methylprednisolone pulse therapy, but the effect is temporary. Pamidronate and thalidomide have been used in some preliminary trials but need further studies to assess their potential role in treating AS patients resistant or intolerant to other forms of treatment. Treatment with tumour necrosis factor blockers is not discussed in this review.

Key words: ankylosing spondylitis, management, treatment, drug therapy, NSAIDs, DMARDs, corticosteroids, disease modification, adverse effects