Nedocromil sodium: a review of the evidence for a dual mechanism of action

A placebo-controlled comparison of ketotifen fumarate and nedocromil sodium ophthalmic solutions for the prevention of ocular itching with the conjunctival allergen challenge model

BACKGROUND

Ketotifen fumarate 0.025% ophthalmic solution and nedocromil sodium 2.0% ophthalmic solution are 2 topical antiallergic medications with different modes of action and efficacy profiles. Both solutions are indicated for ocular itching associated with allergic conjunctivitis.

OBJECTIVE

This study compared the efficacy, safety, and comfort of ketotifen fumarate 0.025% ophthalmic solution and nedocromil sodium 2.0% ophthalmic solution for the prevention of ocular itching, using the conjunctival allergen challenge (CAC) model.

METHODS

This was a single-center, double-masked, contralateral, randomized, placebo- and active-controlled CAC clinical trial. Subjects aged >10 years with a history of allergic hypersensitivity who responded to the CAC at screening visits 1 and 2 qualified for randomization at visit 3. At visit 3 (day 21) and visit 4 (day 35), subjects received 1 of 3 treatments: ketotifen, nedocromil, or placebo (artificial tears), randomized by eye. Allergen challenges were conducted at 5 minutes posttreatment dose (visit 3) and 12 hours posttreatment dose (visit 4). At each visit, subjects evaluated their ocular itching every 30 seconds for 20 minutes. At visit 4, subjects evaluated the comfort of the medication immediately after instillation, at 30 seconds after instillation, and at l, 2, 5, and 10 minutes after instillation. The subjects were also queried about overall eyedrop comfort by choosing from descriptive terms and about overall eyedrop preference based on comfort and perceived efficacy.

RESULTS

Eighty-five subjects were screened for this study. Fifty-nine (28 males, 31 females; mean age, 38.7 years) qualified and were randomized to receive study medications. Ketotifen-treated eyes experienced significantly less ocular itching induced by CAC than nedocromil-treated eyes and those that received placebo at both the 5-minute and 12-hour posttreatment allergen challenges (all P < 0.05). Nedocromil-treated eyes showed no statistical or clinical differences from placebo at any time point. Ketotifen-treated eyes showed no differences in comfort from those that received placebo but were significantly more comfortable than nedocromil-treated eyes at 1, 2, 5, and 10 minutes after instillation (all P < 0.05). On the basis of comfort and subjective efficacy, 60% of subjects preferred ketotifen, 21% preferred nedocromil, and 19% preferred placebo.

CONCLUSION

Ketotifen was significantly more effective and comfortable than nedocromil at both 5 minutes and 12 hours after administration in this CAC model.

Supplementation of fexofenadine therapy with nedocromil sodium 2% ophthalmic solution to treat ocular symptoms of seasonal allergic conjunctivitis

PURPOSE

Ocular symptoms are often under-treated in patients with allergic rhinoconjunctivitis. The efficacy of fexofenadine hydrochloride 60 mg capsules supplemented with nedocromil sodium 2% ophthalmic solution was evaluated to determine the optimal drug regimen for control of ocular allergic symptoms.

METHODS

In this 5-week, open-label, randomized, multicentre comparative study, 89 patients with documented ragweed pollen allergy received fexofenadine b.i.d. with nedocromil rescue, fexofenadine q.d. with nedocromil b.i.d., or fexofenadine rescue with nedocromil b.i.d. during the ragweed pollen season.

RESULTS

For all regimens, mean symptom severity scores for itching, burning, tearing, redness, grittiness, discharge, light sensitivity and swelling improved significantly (P < 0.003). Similarly, all groups experienced significant (P < 0.02) improvement in all clinical signs: erythema, oedema, discharge, conjunctival injection and conjunctivitis, as well as quality-of-life scores (P < 0.0001). All regimens reduced overall symptom severity scores after 5 min (P < 0.05) with relief persisting over 12 h (P < 0.03). Improvements in mean symptoms, signs and quality-of-life scores were similar among the treatment groups as were onset and duration of action even though patients in two of the three study arms were taking one-half or less of the recommended fexofenadine dosage. Patients and physicians judged the regimens containing lower fexofenadine dosages (with nedocromil b.i.d.) to be more effective overall than the regimen containing the highest fexo-fenadine dosage (with nedocromil as rescue only).

CONCLUSIONS

Supplementation of oral fexofenadine therapy with nedocromil sodium 2% ophthalmic solution relieves ocular symptoms of seasonal allergic rhinoconjunctivitis, allowing control of rhinal symptoms with half the recommended dosage of fexofenadine.

Arterial hypoxemia in exercising thoroughbreds is not affected by pre-exercise nedocromil sodium inhalation

It has been reported that pulmonary injury (i.e. capillary stress failure) evoked histamine release from airway inflammatory/mast cells contributes to exercise-induced arterial hypoxemia (EIAH) and that pre-exercise inhalation of nedocromil sodium mitigated EIAH in human subjects 'Med. Sci. Sports Exercise 29, (1997) 10-16'. Because exercise-induced pulmonary hemorrhage due to capillary stress failure is routinely observed in racehorses, we examined whether nedocromil inhalation would similarly benefit EIAH and desaturation of hemoglobin in horses. Two sets of experiments, namely, placebo studies followed in 7 days by pre-exercise nedocromil sodium (30 puffs=60 mg) inhalation experiments were carried out on 7 healthy, sound, exercise-trained thoroughbred horses. In both treatments, arterial and mixed-venous blood-gas/pH measurements were made at rest pre- and post-placebo/drug inhalation, as well as during incremental exercise leading to galloping at 14 m/sec on a 3.5% uphill grade-a workload that elicited maximal heart rate and caused pulmonary hemorrhage in all horses in both treatments, thereby indicating capillary stress failure had occurred. In both treatments, significant (P<0.0001) EIAH of a similar magnitude had developed by 30 sec of maximal exertion, and further significant changes in arterial O(2) tension did not occur as exercise duration progressed to 120 sec. Thus, pre-exercise inhalation of nedocromil sodium was ineffective in modifying the development and/or severity of EIAH in the present study. These findings argue against the airway inflammatory mediator(s) release hypothesis for causing arterial hypoxemia in racehorses.

Topical immunopharmacology of ocular allergies

PURPOSE OF REVIEW

To review the histamine-1 receptor antagonists, mast cell blockers and natural agents with such actions that can be used for the topical treatment of ocular allergies.

RECENT FINDINGS

Increasing evidence indicates that some histamine-1 receptor antagonists have additional actions to inhibit secretion of inflammatory mediators, especially cytokines, from ocular mast cells and other cell types. Emerging information suggests that such actions may be through regulation of intracellular calcium ion levels of NF-kappaB activation.

SUMMARY

A number of available drugs and natural non-prescription agents may have anti-histaminic and anti-inflammatory actions.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.

Anti-inflammatory agent, dexamethasone, does not affect exercise-induced arterial hypoxemia in Thoroughbreds

In view of the suggestion that pulmonary injury-induced release of histamine and/or other chemical mediators from airway inflammatory and mast cells contribute to the exercise-induced arterial hypoxemia (EIAH) in human athletes, we examined the effects of pretreatment with a potent anti-inflammatory agent, dexamethasone, on EIAH and desaturation of hemoglobin in horses. Seven healthy, sound, exercise-trained Thoroughbreds were studied in the control (no medications) experiments, followed in 7 days by intravenous dexamethasone (0.11 mg.kg(-1).day(-1) for 3 consecutive days) studies. Blood-gas measurements were made at rest and during incremental exercise leading to maximal exertion at 14 m/s on a 3.5% uphill grade. Galloping at this workload induced pulmonary hemorrhage in all horses in both treatments, thereby indicating that stress failure of pulmonary capillaries had occurred. In both treatments, significant EIAH, desaturation of hemoglobin, hypercapnia, acidosis, and hyperthermia developed during maximal exercise, but significant differences between the control and dexamethasone treatments were not discerned. The failure of pretreatment with dexamethasone to significantly affect EIAH suggests that pulmonary injury-evoked airway inflammatory response may not play a major role in EIAH in racehorses. However, our observations in both treatments that EIAH developed quickly (being evident at 30 s of exertion) and that its severity remained unaffected by increasing exercise duration (to 120 s) suggest that EIAH has a functional basis, probably related to significant shortening of the transit time for blood in the pulmonary capillaries as cardiac output increases dramatically.

H1-receptor antagonist, tripelennamine, does not affect arterial hypoxemia in exercising Thoroughbreds

It has been suggested that pulmonary injury and inflammation-induced histamine release from airway mast cells may contribute to exercise-induced arterial hypoxemia (EIAH). Because stress failure of pulmonary capillaries and EIAH are routinely observed in exercising horses, we examined whether preexercise administration of an H1-receptor antagonist may mitigate EIAH. Two sets of experiments, placebo (saline) and antihistaminic (tripelennamine HCl at 1.10 mg/kg iv, 15 min preexercise) studies, were carried out on seven healthy, exercise-trained Thoroughbred horses in random order 7 days apart. Arterial and mixed venous blood-gas and pH measurements were made at rest before and after saline or drug administration and during incremental exercise leading to maximal exertion at 14 m/s on 3.5% uphill grade for 120 s. Galloping at this workload elicited maximal heart rate and induced exercise-induced pulmonary hemorrhage in all horses in both treatments, thereby indicating that capillary stress failure-related pulmonary injury had occurred. In both treatments, EIAH, desaturation of hemoglobin, hypercapnia, and acidosis of a similar magnitude developed during maximal exertion, and statistically significant differences between the placebo and antihistaminic studies could not be demonstrated. The failure of the H1-receptor antagonist to modify EIAH significantly suggests that pulmonary injury-induced histamine release may not play a major role in bringing about EIAH in Thoroughbred horses.

Nedocromil sodium ophthalmic solution 2% twice daily in patients with allergic conjunctivitis

In a multicenter, open-label evaluation, 1098 patients with ocular itching and a history of perennial or seasonal allergic conjunctivitis instilled one drop of nedocromil sodium 2% twice daily in each eye. Ocular symptoms, signs, and global improvement were assessed at baseline and 1 month; satisfaction scores, quality-of-life variables, and adverse events were also recorded. Significant improvements from baseline (P<.012) occurred in mean severity scores for itching, burning, stinging, watering, swelling, tired eyes, dryness, gritty sensation, eye pain, foreign-body sensation, and light sensitivity. Physicians reported significant reductions (P<.0001) in bulbar conjunctival redness and swelling. Two thirds of patients (634/954) and three fourths of physicians (710/954) reported at least 75% improvement in overall condition after 1 month. The most common adverse events were burning (2.7%) and unpleasant taste (1.4%); headache (1.2%) and adverse events leading to discontinuation (1.3%) were rare. Patients reported significant improvement (P<.001) in their ability to perform daily activities; 65% were more satisfied with nedocromil than with their typical medication. Physicians would prescribe nedocromil again to 80% of the patients. Nedocromil sodium 2% twice daily was effective and safe for the treatment of symptoms of allergic conjunctivitis, significantly improving quality of life and producing high rates of user and physician satisfaction.

Twice-daily and once-daily nedocromil sodium 2% ophthalmic solution for the treatment of seasonal allergic conjunctivitis

In this 8-week open-label, prospective study, 30 patients with grass pollen allergy and ocular itching instilled nedocromil sodium 2% ophthalmic solution twice daily for a 5-day baseline period, followed by once-daily dosing thereafter. Physicians assessed clinical signs after the twice-daily period and after weeks 1 and 3 of the once-daily period; patients rated ocular symptoms daily. Use of specified rescue medication was permitted. Symptom scores for ocular itching, stinging, redness, swelling, burning, tearing, and light sensitivity did not differ significantly between the dosage periods. Scores for erythema, edema, conjunctival injection, and the entire conjunctiva decreased slightly during once-daily administration; discharge scores were unchanged. Of the 20 patients who used rescue medication, only 5 increased their usage by more than two doses per week during the once-daily period. Eighty-three percent of patients were willing to continue the once-daily regimen during the next allergy season. Physicians rated overall control of seasonal allergic conjunctivitis with once-daily administration as "good" or "moderate" in 100% of the patients; 93% of patients applied those ratings themselves. Nedocromil sodium 2% ophthalmic solution instilled once daily maintains control of symptoms in patients who are established on a twice-daily regimen.

Nedocromil sodium in golfers with seasonal allergic conjunctivitis

To evaluate nedocromil sodium 2% ophthalmic solution for the treatment of seasonal allergic conjunctivitis, 24 golfers with documented ragweed-pollen allergy instilled eyedrops twice daily for 4 days prior to golf-course intervention and 15 minutes before playing a round of golf during peak ragweed season. Ocular symptoms were scored at baseline (7 days before golfing), prior to instillation on the day of golf, and 30 minutes, and 1, 4, 8, and 12 hours after tee-off. Physician assessment was performed prior to tee-off, before tee-off on the ninth hole, and at the end of the 18th hole. Itching, burning, grittiness, tearing, redness, and light sensitivity were significantly decreased after nedocromil administration, as were erythema, edema, conjunctival hyperemia, and overall findings in the conjunctiva. Symptom severity scores fell approximately 30 minutes after instillation, with improvements persisting 8 and 12 hours after treatment. Most patients (92%) rated the treatment moderately or completely effective, and 83% were willing to continue its use. Physician assessments of effectiveness agreed with those of the patients. In this open-label study, nedocromil sodium eyedrops relieved the ocular symptoms of seasonal allergic conjunctivitis for up to 12 hours, well beyond a usual round of golf.

Overview of ocular allergy treatment

A plethora of drugs is available for the treatment of ocular allergy. Traditional treatment includes antihistamine and antihistamine/vasoconstrictor combination eyedrops. These drugs are useful, safe, and readily available. Mast cell stabilizers are safe, effective, and an important component of antiallergic therapy. Nonsteroidal anti-inflammatory drugs also have antiallergic effects. In recent years, drugs with multiple mechanisms of action have proven to be effective antiallergics. These drugs often have mast cell stabilizing, antihistaminic, and anti-inflammatory properties. Corticosteroids are considered to be more potent than other antiallergic drugs, and modifications in their molecular structures have made certain corticosteroids suitable for the treatment of ocular allergy.

Efficacy and acceptability of nedocromil sodium 2% and olopatadine hydrochloride 0.1% in perennial allergic conjunctivitis

In this 2-week, randomized, crossover study, ophthalmic solutions of nedocromil sodium 2% and olopatadine hydrochloride 0.1% were compared for effectiveness and acceptability in 28 patients with perennial allergic conjunctivitis and previous olopatadine experience. Patients received nedocromil twice daily or olopatadine twice daily for 1 week, then were crossed over to the alternate medication for 1 week. Outcome measures were patient satisfaction (questionnaire), severity of ocular symptoms (daily diary scores), clinical signs (physician assessments), quality of life (questionnaire), and global assessments of effectiveness. Both medications were well accepted. Of the 28 patients, 16 (57.1%) would request a nedocromil prescription, 10 (35.7%) an olopatadine prescription (P = .157); 22 patients (78.6%) would recommend nedocromil to other allergy sufferers, while 18 (64.3%) would recommend olopatadine (P = .480). Light sensitivity scores were significantly lower with nedocromil (P = .0125); other symptom scores were comparable between medications. Both drugs significantly (P < .01) and comparably decreased erythema, conjunctival injection, and overall conjunctival signs from baseline. Comparable improvement also occurred in quality-of-life scores. Both physicians and patients judged nedocromil and olopatadine to be similarly effective in preventing signs and symptoms. Nedocromil sodium 2% is an effective treatment for perennial allergic conjunctivitis. Patients receiving olopatadine can be switched to nedocromil with no loss in efficacy or satisfaction, but with a reduction in cost.