Development and Validation of Analytical Methods for the Determination of Some Dermatological Drugs A Thesis Presented by Amaal Abdullah Al-Tahami B. Pharm. Sci. (1993) Faculty of Pharmacy, Sana’a University M. Pharm. Sci. (2001) Faculty of Pharmacy, Jordan University Submitted for The Degree of Doctor of Philosophy in Pharmaceutical Sciences (Pharmaceutical Chemistry) Supervised By Prof. Dr. Asmaa Ahmed El-Zaher Professor of Pharmaceutical Chemistry Faculty of Pharmacy Cairo University Ass. Prof. Dr. Ehab Farouk El-Kady Associate Professor of Pharmaceutical Chemistry Faculty of Pharmacy Cairo University Faculty of Pharmacy Cairo University 2018 1 Abstract: This thesis is concerned with the development of simple and accurate methods for the determination of some dermatological drugs, namely; betamethasone dipropionate, clioquinol, clobetasol propionate, diflucortolone valerate, econazole nitrate, fusidic acid, hydrocortisone, metronidazole benzoate, miconazole nitrate, mometasone furoate, salicylic acid and triamcinolone acetonide either alone or in combination with other drugs. Different methods have been introduced for determination of the analyzed drugs in their pure form, laboratory prepared mixture and in pharmaceutical dosage forms. 2 Introduction Dermatosis is a term that refers to diseases of the integumentary system. This classification includes everything on the surface of the body: skin, nails, and hair. Any condition affecting the skin could be categorized a dermatosis. Skin has several layers, including the epidermis, the dermis, and the subcutaneous tissue Figure 1. A dermatosis may involve changes in any or all of these skin layers[1]. Figure 1: Skin layers Some of the most common dermatological disorders: Table 1: some of the most common dermatological disorders Name Description [2] Causes [3] Oil glands in skin cause pimples Acne Bacteria and hormone and scarring Alopecia Hair loss around patches Autoimmune disorders areata Impetigo Skin infection Bacteria Keratosis Crusty pre-cancerous growths Sun damage The most serious form of skin Melanoma Genetic susceptibility cancer basal 3 Nails curve around the fingertips Nail due to low oxygen levels in the Various types of lung disease clubbing blood Several causes such as The fingernails become loose and Onycholysis (Trauma, infection, and skin separate from the nail bed disease) Characterized by patches of Psoriasis Autoimmune disorders abnormal skin Fungal infection of skin that Tinea Fungus leaves round marks Vitiligo White of patches of skin Autoimmune disorders Dermatological formulation Different dosage forms (e.g. creams, ointments, gels, pastes, suspensions, lotions, foams, sprays, aerosols, and solutions) containing special topical agents are directly applied to the malfunctioning skin to treat a specific disease or alleviate a condition. A unique aspect of dermatological pharmacology is the direct accessibility of the skin as a target organ for the diagnosis and treatment. Therapeutic agents can reach epidermal keratinocytes and immunocompetent cells in the epidermis and the underlying dermis that are involved in the pathogenesis of numerous cutaneous diseases. Topical agents can be applied directly to the skin but must penetrate into the tissue to achieve efficacy. Appropriate use of topical agents requires an appreciation of the factors that influence percutaneous absorption [4]. On the other hand, there are a lot of dermatological drugs used systemically involving several route of administration: oral, intramuscular (e.g., methotrexate, glucocorticoids), intravenous (e.g., immunoglobulin, alefacept) or subcutaneous (e.g., eflizumab, etanercept)[4]. Most common drugs for dermatological disorders: 1- Corticosteroids Corticosteroids have immunosuppressive and anti-inflammatory properties. They are used for treatment of psoriasis, eczema, contact dermatitis, and other skin conditions manifested by itching and inflammation [5]. Topical corticosteroids act by binding to a specific receptor in the cellular cytoplasm and modulating the transcription of multiple genes. This leads to the suppression of the production of inflammatory 4 substances such as prostaglandins and leukotrienes, and also inhibits the recruitment of inflammatory cells into the skin[6]. There are many topical steroids available, and they differ in potency and formulation Table 2. Table 2: Most commonly used corticosteroids for dermatological disorders: Generic Name Chemical Structure Alclometasone dipropionate Amcinonide Betamethasone dipropionate Clobetasol propionate Desonide Diflucortolone valerate Flucinolone acetonide 5 Fluticasone propionate Halobetasol propionate Hydrocortisone Mometasone furoate Triamcinolone acetonide 2- Antibacterial agents: Majority of skin infections are caused by Gram-positive bacteria, most commonly Staphylococcus aureus and group A β-hemolytic Streptococcus (GABHS). Some Gram-negative organisms and anaerobes may also cause pyogenic skin infections. Other organisms like Mycobacteria sp. and Treponema pallidum may also cause infections. Topical antibacterial agents may be useful in preventing infections in clean wounds, in the early treatment of infected dermatosis and wounds [5]. Each class of antibacterial drugs has a unique mode of action which is summarized in (inhibition of cell wall synthesis, inhibition of protein synthesis, inhibition of nucleic acid synthesis, alteration of cell membrane function or alteration of cell metabolism)[7]. Some topical anti-infectives contain corticosteroids in addition to antibiotics. There is no convincing evidence that topical corticosteroids inhibit the antibacterial effect of 6 antibiotics when the two are incorporated in the same preparation. In the treatment of secondarily infected dermatoses, which are usually colonized with streptococci, staphylococci, or both, combination therapy may prove superior to corticosteroid therapy alone. Antibiotic-corticosteroid combinations may be useful in treating diaper dermatitis and impetiginized eczema [8]. Table 3: Most commonly used antibacterial agents for dermatological disorders: Generic Name Chemical Structure Erythromycin Clindamycin Mupirocin Fusidic acid 3-Antifungal agents: The treatment of superficial fungal infections caused by dermatophytie fungi may be accomplished with topical antifungal agents Table 4. Topical antifungal corticosteroid fixed combinations have been introduced on the basis of providing more rapid symptomatic improvement than an antifungal agent alone. [4] Azole antifungal drugs inhibit the enzyme lanosterol 14 α-demethylase; the enzyme necessary to convert lanosterol to ergosterol. Depletion of ergosterol in fungal membrane disrupts the 7 structure and many functions of fungal membrane leading to inhibition of fungal growth [9]. Table 4: Most commonly used antifungal agents for dermatological disorders: Generic Name Chemical Structure Butenafine Clotrimazole Econazole nitrate HNO3 Fluconazole Ketoconazole Miconazole nitrate HNO3 8 4- Agents for acne: Acne, also known as acne vulgaris, is a long-term skin disease that occurs when hair follicles are clogged with dead skin cells and oil from the skin. It is characterized by blackheads or whiteheads, pimples, oily skin, and possible scarring. It primarily affects areas of the skin with a relatively high number of oil glands, including the face, upper part of the chest and back [10]. Many treatment options for acne are available, including lifestyle changes, medications, and medical procedures. Eating fewer simple carbohydrates such as sugar may help. Treatments applied directly to the affected skin, such as azelaic acid, benzoyl peroxide, and salicylic acid, are commonly used . Antibiotics and retinoids are available in formulations that are applied to the skin and taken by mouth for the treatment of acne Table 5. Isotretinoin pills are usually reserved for severe acne due to greater potential side effects [10]. Table 5: Most commonly used agents of acne for dermatological disorders: Generic Name Chemical Structure Azelaic acid Benzoyl peroxide Isotretinoin 5-Agents for pigmentation disorders Agents for pigmentation disorders include hydroquinone and methoxsalen, which are used for the treatment of hyperpigmented skin condition and vitiligo, respectively [5]. 9 Hydroquinone, monobenzone and mequinol (the monomethyl ether of hydroquinone) are used to reduce hyperpigmentation of the skin Table 6. Topical hydroquinone and mequinol usually result in temporary lightening, where a monobenzone causes irreversible depigmentation The mechanism of action of these compounds appears to involve inhibition of the enzyme tyrosinase, thus interfering with the bio-synthesis of melanin. In addition, monobenzone may be toxic to melanocytes, resulting in permanent loss of these cells. Some percutaneous absorption of these compounds takes place, because monobenzone may cause hypopigmentation at sites distant from the area of application. Both hydroquinone and monobenzone may cause local irritation. Allergic contact dermatitis to these compounds can occur. Prescription combinations of hydroquinone, fluocinolone acetonide, and retinoic acid (Tri-Luma®) and mequinol and retinoic acid (Solage®) are more effective than their individual components. Methoxsalen is a photoactive substance that stimulates melanocytes and is used as a repigmentation agent for patient with vitiligo [5]. Table 6: Most commonly used agents of pigmentation for dermatological disorders: Generic Name Chemical Structure Hydroquinone Mequinol Methoxsalen