Determination of the Particulate Size and Aggregation of Clonidine and Corticosteroids for Epidural Steroid Injection

Background: Epidural injection of corticosteroids is a commonly used treatment forradicular pain. However, the benefits are often short lived, and repeated injections are oftenlimited secondary to concerns of side effects from cumulative steroid doses. In addition, rare,catastrophic complications, including brain and spinal cord embolic infarcts have been attributedto particulate steroid injections. A previous study has shown that dexamethasone has lessparticulate than other corticosteroids, possibly reducing embolic risk. Furthermore, a recent studyindicated that clonidine may be useful in the treatment of radicular pain when administered viaepidural steroid injection. The combination of corticosteroid and clonidine is an intriguing, yetunstudied, alternative to traditional treatment.Objective: Our study examines whether mixing clonidine and various corticosteroids results inincreased particle size or aggregation.Methods: Evaluations under light microscopy for particle size were made of samples of clonidinealone and clonidine mixed with equal parts of 3 corticosteroids solutions: dexamethasone sodiumphosphate injection, triamcinolone acetonide injectable suspension, and betamethasone sodiumphosphate and betamethasone acetate injectable suspension. Four mL each of clonidine (100 μcg/mL), clonidine (100 μcg/mL) + dexamethasone sodium phosphate injection (4 mg/mL), clonidine(100 μcg/mL) + triamcinolone acetonide injectable suspension (40 mg/mL), and clonidine (100μcg/mL) + betamethasone sodium phosphate and betamethasone acetate injectable suspension(6 mg/mL) were examined Their particle sizes were compared to measurements taken when eachsteroid solution was examined alone.Results: Clonidine was determined to be nonparticulate when examined by light microscopy.Clonidine mixed with equal parts of each of the 3 corticosteroids mentioned above did not resultin increased clumping or increased particle size over each of the corticosteroids measured alone.Conclusion: Mixing clonidine with corticosteroids did not increase particulation compared tocorticosteroids alone. Combining clonidine and corticosteroids for epidural injection may proveto be a useful treatment for radicular pain. The combination of these is unlikely to result in asolution that is more likely to cause embolic infarcts than the use of corticosteroids alone.Key words: steroid, epidural, clonidine, injection, particulate, aggregation