Various topical ophthalmic products are used to treat allergic conjunctivitis. However, due to the clinical variability between allergic patients, one medication cannot successfully treat all patients all of the time. This is why newer options become available every day (Bielory 2000).
Olopatadine hydrochloride 0.1% (Patanol®; Alcon Laboratories, Fort Worth, TX, USA) is an H1 receptor blocker and mast cell stabilizer. Its dual action provides rapid onset and prolonged duration of therapeutic action, which allows twice daily dosage (Abelson 1998; Abelson & Spitalny 1998). In previous studies, olopatadine hydrochloride demonstrated significantly greater efficacy than placebo, mast cell stabilizers, NSAIDs and some other drugs (Spangler et al. 2001; Yaylali et al. 2003; Leonardi & Zafirakis 2004). We designed a single-centre, randomized, prospective study to compare the efficacy of olopatadine hydrochloride with that of artificial tears (Tears Naturale II®, Alcon Laboratories, Fort Worth, TX, USA), which are used as diluents. The environmental model was preferred to observe the effect of both drugs during daily airborne allergen exposure.
A total of 51 patients (12 males, 39 females), aged between 14 and 49 years (mean 24.8 years), with symptoms and signs of seasonal allergic conjunctivitis (SAC), were enrolled. All patients had discontinued the use of any ophthalmic medication for at least 4 weeks. Informed consent was obtained from all patients.
The study was completed during the spring, when patients with SAC showed maximum signs and symptoms of the disease, in order to avoid variance in allergen exposure between patients. It included a total of four visits. The first was the baseline screening visit. Demographic data and visual acuities were recorded and each patient underwent a slit-lamp examination to score conjunctival hyperaemia, chemosis, mucous discharge and lid oedema according to the grading steps defined by Abelson (1998). Ocular itching and lacrimation were scored according to a questionnaire. Each subject was dispensed two masked bottles, one of which held olopatadine hydrochloride 0.1%, while the other held artificial tears. Patients were instructed to use both bottles twice a day and were required to wear sunglasses and avoid the use of make-up. The eye to use olopatadine ophthalmic solution was randomly assigned using sealed envelopes. Follow-up clinic visits were scheduled for the first, second and fourth weeks of treatment. All procedures were repeated at all visits. Statistical analysis was performed using Mann–Whitney U-test.
All the patients had completed the study at the end of 4 weeks. The mean scores of the parameters were computed for each examination (Table 1). The scores for eyes receiving olopatadine hydrochloride treatment were already significantly lower at the end of the first week for all parameters, except for lid oedema and mucous discharge, which showed a trend toward lower scores (p = 0.09 and p = 0.07, respectively). By the end of the second week the treatment response for these parameters also favoured olopatadine hydrochloride (p = 0.01 and p = 0.02).
|Baseline||Week 1||Week 2||Week 4|
|Olopatadine||2.59 (1.5–4.0)||1.67 (0.0–3.5)||1.13 (0.0–3.0)||0.93 (0.0–2.0)|
|Artificial tears||2.59 (1.5–4.0)||2.21 (0.5–3.5)||2.04 (0.5–3.5)||1.98 (0.5–3.5)|
|p-value*||1.000||0.003||< 0.001||< 0.001|
|Olopatadine||1.29 (0.0–3.0)||0.92 (0.0–2.0)||0.49 (0.0–2.0)||0.26 (0.0–2.0)|
|Artificial tears||1.29 (0.0–3.0)||1.23 (0.0–3.0)||1.18 (0.0–3.0)||1.12 (0.0–3.0)|
|p-value*||1.000||0.009||< 0.001||< 0.001|
|Olopatadine||2.01 (1.0–3.5)||1.13 (0.0–2.0)||0.78 (0.0–2.0)||0.56 (0.0–1.0)|
|Artificial tears||2.01 (1.0–3.5)||1.78 (1.0–3.0)||1.64 (0.5–3.0)||1.49 (0.5–3.0)|
|p-value*||1.000||< 0.001||< 0.001||< 0.001|
|Olopatadine||0.78 (0.0–3.0)||0.33 (0.0–2.0)||0.09 (0.0–2.0)||0.04 (0.0–1.0)|
|Artificial tears||0.75 (0.0–3.0)||0.67 (0.0–3.0)||0.60 (0.0–2.0)||0.45 (0.0–2.0)|
|p-value*||0.846||0.021||< 0.001||< 0.001|
|Olopatadine||0.61 (0.0–2.0)||0.36 (0.0–2.0)||0.26 (0.0–1.5)||0.10 (0.0–1.0)|
|Artificial tears||0.59 (0.0–2.0)||0.58 (0.0–2.0)||0.57 (0.0–2.0)||0.50 (0.0–2.0)|
|Olopatadine||0.44 (0.02–2.0)||0.23 (0.0–2.0)||0.09 (0.0–1.0)||0.03 (0.0–1.0)|
|Artificial tears||0.44 (0.0–2.0)||0.38 (0.0–2.0)||0.28 (0.0–1.0)||0.24 (0.0–1.0)|
Mean values for itching decreased from 2.58 (at baseline) to 0.93 at the end of the study. For conjunctival hyperaemia, there was a significant treatment response favouring olopatadine hydrochloride over artificial tears at week 1 (p < 0.001) and week 4 (p < 0.001). Evaluation of other ocular signs at 4 weeks showed lower scores in olopatadine-treated patients.
The use of artificial tears also elicits a therapeutic effect, in part because of the dilution of allergens (Table 1). However, a more detailed analysis of the data revealed that olopatadine hydrochloride exhibited a larger reduction in all parameters in the study. The environmental study model used in our study limited the standardization and reproducibility of our results as patients were exposed to varying amounts of allergen during the study. To minimize this fluctuation, all subjects were evaluated within the same month.
The efficacy observed in this study is consistent with patient preferences observed in previous studies. Further, these results in an environmental model confirm the results of previous conjunctival allergen challenge studies that have evaluated the efficacy of olopatadine in a variety of settings.