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Nedocromil sodium, a non-toxic pyranoquinoline dicarboxylate, was developed as a novel topical treatment for allergic inflammatory lung diseases. With a broader pharmacological potential than the chromone compound sodium cromoglycate, nedocromil sodium has more potent antiinflammatory effects whilst maintaining a good safety profile due to rapid excretion, unmetabolized. Having the ability to stabilize both mucosal (MC(T)) and connective tissue (MC(TC)) mast cells and directly to inhibit activated cells such as eosinophils, which are involved in continuing allergic inflammation in the eye as well as in the airways, nedocromil sodium appears ideally suited to the treatment of allergic conjunctivitis. Preliminary therapeutic trials have confirmed efficacy and the lack of side-effects of the 2% eye drop formulation of nedocromil sodium, and its comparative potency which permits twice-daily administration for seasonal ocular symptoms, with the safe option of increasing to four times daily use for more severe, chronic allergic inflammatory conditions. With many patients already symptomatic at the start of trial treatment, nedocromil sodium eye drops have also proved to have a rapid onset of action providing relief of symptoms in 24 hours in the majority of cases, and often within one hour of the first dose.

Tilarin is a nasal spray containing 1% nedocromil sodium, a non-toxic pyranoquinoline dicarboxylate compound with potent antiallergic antiinflammatory properties. As a first-line topical treatment for seasonal allergic rhinitis (SAR) the pharmacokinetics of nedocromil sodium nasal formulation are such that it rivals sodium cromoglycate for safety. Less than 8% of the total dose of nedocromil sodium is systemically absorbed from the nasal mucosa, and this is reversibly bound to plasma proteins and is cleared rapidly from the circulation. Nedocromil sodium is eliminated unmetabolised in the urine and faeces, with an elimination half-life of 5.3 +/- 0.9 minutes. No significant adverse effects have been reported following intranasal administration of 1% nedocromil sodium four times daily, to a total of 964 patients with allergic rhinitis during clinical trials. Laboratory studies have shown that nedocromil sodium has a more wide-ranging pharmacological antiinflammatory profile than sodium cromoglycate and this is manifest in its clinical efficacy in allergic asthma and rhinoconjunctivitis. Analysis of pooled data from a series of double-blind, placebo-controlled group comparative studies in SAR patients demonstrated that, despite a significantly lower use of rescue antihistamines than with placebo treatment (31% reduction; p = 0.005), four times daily dosage with nedocromil sodium 1% nasal spray significantly reduced daily symptoms of rhinitis (p < 0.001) and was considered effective by the majority of patients (p < 0.001). Specific examples of the therapeutic efficacy of nedocromil sodium compared with placebo in patients with grass or ragweed pollen SAR can be found in the literature. One ragweed study (1) included four times daily sodium cromoglycate 4% nasal spray as an active comparator and showed a consistent, if non-significant, trend in favour of nedocromil sodium 1%, which was the more effective drug in comparison to placebo. An Italian paediatric study (2) compared nedocromil sodium 1% nasal spray with placebo in 149 children of whom 72% were under twelve years of age. After one week, the clinicians observed a significant reduction (p = 0.03) in sneezing with nedocromil sodium and after four weeks, patient (p < 0.01) and clinican (p < 0.001) opinions favoured the active treatment. Overall, the clinical profile of topical nedocromil sodium in SAR demonstrates fast relief of existing symptoms, sustained efficacy with four times daily use during peak pollen challenge, and a reduced need for concomitant symptomatic therapies. Nedocromil sodium 1% nasal spray is well tolerated, with minimal side-effects, and is acceptable to a wide age-range of patients.

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