Are prostaglandins major mediators in perennial allergic rhinitis?

Certain prostaglandins acting as inflammatory mediators have been implicated in the aetiology of perennial allergic rhinitis (PAR). Inhibition of prostaglandin synthesis in the nasal mucosa might therefore influence the symptoms associated with PAR. A randomised, doubleblind, placebo-controlled cross-over trial using 0.1% Diclofenac eye-drops has been conducted to investigate this hypothesis. Diclofenac, a non-steroidal anti-inflammatory drug (NSAID), reduces prostaglandin synthesis through the inhibition of the cyclo-oxygenase pathway. Twenty-five patients with significant PAR and positive skin tests to relevant perennial allergens were recruited and two drops of the given preparation were administered bilaterally q.d.s.. Thirteen patients completed the study. Nasal symptom score (itch, rhinorrhoea, sneezing, and blockage), smell test score, saccharin transit time, total nasal airflow resistance, and nasal inspiratory peak flow measurements were obtained at each of three study visits. No significant treatment effects were found. The daily nasal symptom score over the entire study period showed no significant variation. Adverse effects such as local invitation, dry nose or throat were rare. No untoward changes in haematological, biochemical profiles and urinalysis occurred. In conclusion, topical 0.1% Diclofenac eye-drops applied nasally have no significant effect on PAR. Prostaglandins alone may not play a major role in mediation of symptoms in this condition.