chitosan and plga microspheres as drug delivery ... - UniCA Eprints

1. General Introductionhighly vascularized, which makes pulmonary targeting difficult because of fast absorption ofmost drugs (especially lipophilic and low molecular weight drugs).1.4. Pulmonary Drug Delivery Following Aerosol TherapyThere are several advantages in delivering drugs, such as antimicrobial agents, to the lungsincluding a non invasive method of delivery; a large surface area for absorption (~75m 2 ); thin(0.1 to 0.5 µm) alveolar epithelium, permitting rapid absorption; absence of first-passmetabolism; rapid onset of action; and high bioavailability.Since the advent of nebulizer therapy in 1859, nebulizers have been used to treat a range ofpulmonary diseases in pediatric and adult populations, including asthma, chronic obstructivepulmonary disease (COPD), and cystic fibrosis (CF).The expansion of nebulizer therapy inthe mid to late 20th century for common respiratory diseases has been followed by a focus onuse for more specific indications and certain new applications.The development of an inhalant therapy that is efficacious and safe depends not only on apharmacologically active molecule, but also on a well-designed delivery system andformulation. It is the optimization of the whole system (drug, drug formulation and device)that is necessary for the successful development of inhalation therapies, both new and old, forthe treatment of local and systemic diseases. Drug–device combinations must aerosolize thedrug in the appropriate particle size distribution and concentration to ensure optimaldeposition and dose in the desired region of the lung.Although the traditional form of inhalation therapy dates back to the earliest records ofancient cultures, the advantages of inhalation therapy have essentially remained the same.Several studies (1–3) have demonstrated the clinical advantage of inhalation aerosols oversystemic therapy for the treatment of lung disorders. Relatively small doses are required foreffective therapy, reducing systemic exposure to drug and thus minimizing adverse effects.Delivering small doses of active ingredients directly to the lung effectively targets the drug,thereby maximizing therapeutic effect while minimizing adverse effects.1.4.1. Delivery Device: Jet NebulizerNebulizers have been used for many years to treat asthma and other respiratory diseases.There are two basic types of nebulizer, jet and ultrasonic nebulizers. Ultrasonic nebulizersutilize high frequencies to convert liquid into a fine mist (74).18