Jawaharlal Nehru Technological University Hyderabad B.Pharmacy II Year PHYSICAL PHARMACEUTICS-I Previous Question Paper (August/September - 2022 - R17)

Amorphous substances lack a defined crystalline lattice structure, resulting in a random molecular arrangement. They exhibit higher solubility and faster dissolution rates than crystalline forms due to their higher internal energy and lack of a crystal lattice energy barrier. However, they are often physically unstable and prone to recrystallization. Polymorphic substances exist in more than one crystalline form, where molecules pack differently in the crystal lattice. Polymorphs differ in physical properties such as melting point, density, and solubility, which significantly impacts the bioavailability of drugs.

Applications include: 1. Enhancing the bioavailability of poorly water-soluble drugs by utilizing amorphous solid dispersions. 2. Selecting the most stable polymorph during formulation development to ensure consistent shelf-life and therapeutic efficacy. 3. Controlling drug release rates through the selection of specific polymorphic forms.

Relative humidity (RH) is the ratio of the actual amount of water vapor present in the air to the maximum amount of water vapor the air could hold at the same temperature, expressed as a percentage. It is a critical parameter in pharmaceutical stability testing because it dictates the moisture content of solid dosage forms. High RH can lead to drug degradation, changes in physical state, or microbial growth.

Aerosols are pressurized dosage forms containing one or more active ingredients which, upon actuation, emit a fine dispersion of liquid or solid particles in a gaseous medium. They consist of a propellant, a product concentrate, and a container with a valve assembly. The interaction between the formulation and the environment, particularly moisture ingress or loss, is influenced by the integrity of the aerosol system. Relative humidity is specifically monitored during the storage and stability testing of aerosols to ensure the valve mechanism and container seals remain effective against environmental moisture, preventing corrosion or phase separation within the canister.