Rosacea: An Introduction

Background

Many people are affected by inflammatory skin disorders that result in unsightly and painful rashes, acne, persistent red veins, and acne-like skin eruptions, such as macules, nodules, and pustules that may ooze or crust. Inflammatory skin disorders often result in intense psychosocial distress. Rosacea is a common inflammatory skin disorder affecting over 10 million people in the United States. Rosacea generally involves the cheeks, nose, chin, and forehead and the typical age of onset is 30 to 60 years. See e.g., Zuber T. J., Rosacea: Beyond First Blush 32 HOSP. PRACT. 188-189 (1997); THE MERCK MANUAL 813-814 (Keryn A. G. Lane et al. eds. 17.sup.th ed. 2001). Many people with early-stage rosacea incorrectly assume that they suffer from adult acne, sun or windburn, or the normal effects of aging.

Rosacea develops gradually starting as frequent blushing and frequent irritation of the facial skin.

More advanced rosacea is characterized by a vascular stage where patients display increasingly severe erythema (abnormal redness of the skin) and telangiectasia (visible red lines due to abnormal dilatation of capillary vessels and arterioles). Pimple-like eruptions, which may be solid (called papules or nodules) or puss filled (known as pustules) may develop. Such eruptions often look like acne, but whiteheads or blackheads (common symptoms of acne) are not normally present. Later-stage rosacea is characterized by rhinophyma (enlargement of the nose). If left untreated, rosacea can progress to irreversible disfigurement. Rosacea symptoms are often aggravated by sun exposure, changes or extremes in temperature, wind, and consumption of certain foods, such as spicy foods, caffeine, and alcohol.

The exact pathogenesis of rosacea is unknown, but the pathologic process is well described. For example, erythema associated with rosacea is caused by dilation of the superficial vasculature of the face. Zuber T. J., Rosacea: Beyond First Blush 32 HOSP. PRACT. 188-189 (1997).

There is no known cure for rosacea. Current treatments, which are directed to control of redness, inflammation, and skin eruptions, are of limited effectiveness in many patients and, generally, can be used only for a limited duration. Standard treatments include avoidance of triggers such as sun exposure, wind exposure, alcohol consumption, spicy foods, and irritating facial cleansers, lotions, and cosmetics. Antibiotics are the traditional first line of therapy. Long-term treatment (5 to 8 weeks or more) with oral antibiotics such as tetracycline, minocycline, doxycycline or clarithromycin may control skin eruptions. Alternative oral treatments include vitamin A medications, such as isoretinoin and antifungal medications. Unfortunately, such oral medications often cause side effects and many people have limited tolerance. Topical treatments, such at topically applied antibiotics and antifungals (such as metronidazole) or steroids, are available but also have limited effectiveness and cannot treat all symptoms. For example, isoretinoin has serious teratogenic side-effects and female patients of child bearing age must use effective birth control or avoid the therapy. Topical treatments include topically applied metronidazole, topically applied steroids, topically applied azelaic acid, topically applied rentinoic acid or retinaldehyde, and topical vitamin C preparations are available but have limited effectiveness and cannot treat all symptoms. Surgery, such as the laser elimination of blood vessels, is typically a last resort, but may be prescribed if other treatments are ineffective. In patients with nose hyperplasia, surgical reduction may improve the patient's cosmetic appearance, but does not treat the disease itself. Mixed light pulse (photoderm) therapy has proved somewhat effective for certain rosacea symptoms in some patients. Thus, there remains a need for topical formulations for treatment of rosacea and its symptoms.

Agonists of the .alpha..sub.2 adrenoceptors have been used therapeutically for a number of conditions including hypertension, congestive heart failure, angina pectoris, spasticity, glaucoma, diarrhea, and for the suppression of opiate withdrawal symptoms (J. P. Heible and R. R. Ruffolo Therapeutic Applications of Agents Interacting with .alpha.-Adrenoceptors, p. 180-206 in Progress in Basic and Clinical Pharmacology Vol. 8, P. Lomax and E. S. Vesell Ed., Karger, 1991).

Adrenoceptor agonists such as clonidine have been primarily used orally, though a patch formulation is known. The goal of existing formulations is to deliver a systemic internal dose of the compound to the patient. The .alpha..sub.2 agonists are known to mediate vasoconstriction both in the core and periphery of a patient. In particular .alpha..sub.2 adrenoceptor agonists are known to cause vasoconstriction of peripheral arterioles, in response to stimulation due to cold or stress.

A number of patents describe the use of brimonidine for treating ophthalmic conditions and eye diseases. In Canadian patent No. CA2326690, there is described the use of topical ophthalmic preparations for use only in the eyes, to treat eye diseases. The Canadian patent discusses the problems with ophthalmic preparations taken topically (in the eye), orally or parenterally, and their systemic effects, including some serious, that limit their use. These systemic effects include, cardiopulmonary effects of .beta.-blockers like timolol; dryness of mouth, flush, fever, tachy cardia, urinary retention, convulsion and irritability with atropine; hypertension with phenylephine; increased salivation, nausea, vomiting, diarrhea, stomach cramps, bronchial secretions, brionchial constriction, asthma, bradycardia, paresthesia with miotics; hypotension with clonidine; and dry mouth, fatigue and drowsiness with apraclonidine and brimonidine.

There has been no composition containing .alpha..sub.2 adrenoceptor agonists that can deliver a dose of the agonist to the patient, ameliorating the symptoms of rosacea, without causing systemic side effects. There has also been no topical skin composition containing .alpha..sub.2 adrenoceptor agonists that can deliver a dose of the agonist to the skin of the patient, ameliorating the symptoms of rosacea, without causing systemic side effects.


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