Intramuscular corticosteroid injections in seasonal allergic rhinitis: A systematic review

Seasonal allergic rhinitis (SAR) is an exaggerated immunological reaction to allergens (pollen) in the air. In a small subgroup of patients, SAR can be difficult to control with first-line therapy. Intramuscular corticosteroid injections (IMCIs) are an additional treatment in this subgroup of SAR patients. The aim of this systematic review is to investigate the efficacy and safety of IMCIs in SAR.

Titles and abstracts were independently screened, followed by full-text screening based on predefined criteria. Included articles were critically appraised using the Cochrane Risk of Bias 2 (RoB 2) tool. The primary outcome is reported as the final conclusion about efficacy that was stated in the included studies. The secondary outcome is the safety of IMCIs with regard to long lasting side-effects.

The search yielded 2139 records, of which 10 were relevant and valid for our clinical question. Critical appraisal showed high risk of bias, which was due to unclear description of methods. Four out of four placebo-controlled, randomized controlled trials reported a significant and relevant difference in efficacy in favor of IMCIs compared with placebo. The occurrence of side-effects was not different between IMCIs and placebo or oral corticosteroids (OCs).

The outcome of this systematic review on trials concerning intramuscular steroid injections, despite being based on individual studies claiming favorable outcome with their use, is "inconclusive." This is because of the epidemiological high risk of bias in these studies that were mostly executed more than 30 years ago. The "inconclusive" rating allows for a description as an "optional therapy" for severe cases in guideline formation.