JNTU B.Pharmacy I PHARMACEUTICS- I Previous Question Paper (September/October-2021 - R17)

A dosage form is the physical form of a dose of a chemical compound used as a drug or medication intended for administration or consumption. It is the means by which drug molecules are delivered to the site of action within the body to produce the desired therapeutic effect.

Dosage forms are classified based on their physical state and route of administration:

1. Solid Dosage Forms: These are stable and convenient for transport and administration.
   Examples: Tablets (Paracetamol), Capsules (Amoxicillin), Powders (ORS), and Suppositories (Glycerin).
2. Liquid Dosage Forms: These are mixtures of drug substances in a suitable vehicle, categorized as monophasic (solutions) or biphasic (emulsions, suspensions).
   Examples: Syrups (Cough syrup), Elixirs (Paracetamol elixir), Suspensions (Antacid), and Emulsions (Cod liver oil).
3. Semi-solid Dosage Forms: These are intended for topical application on skin or mucous membranes.
   Examples: Ointments (Betamethasone), Creams (Cold cream), Pastes (Zinc oxide paste), and Gels (Diclofenac gel).
4. Gaseous Dosage Forms: These involve drugs administered via inhalation to reach the respiratory tract or systemic circulation.
   Examples: Aerosols (Salbutamol inhaler) and Sprays (Nasal sprays).

The selection of a dosage form depends on factors such as the stability of the drug, the required onset of action, the patient's age, and the site of administration.

Posology is the branch of pharmacy that deals with the study of doses or the quantitative determination of the amount of a drug to be administered to a patient to produce the desired therapeutic effect.

The factors affecting posology include:

• Age: Infants and elderly patients often require smaller doses compared to adults due to differences in drug metabolism and excretion.
• Body Weight: Doses are often calculated based on body weight or surface area to ensure therapeutic consistency, especially in pediatric patients.
• Sex: Physiological differences, such as hormonal variations and body composition, can influence drug response.
• Route of Administration: Intravenous doses are typically smaller than oral doses because the drug enters the systemic circulation directly, bypassing the first-pass metabolism.
• Time of Administration: Certain drugs may cause irritation or have altered absorption depending on whether they are taken on an empty or full stomach.
• Environmental Factors: Factors like climate and occupation can influence the patient's physiological state and drug requirements.
• Presence of Disease: Impaired renal or hepatic function significantly affects the clearance of drugs, necessitating dose adjustments to prevent toxicity.
• Tolerance and Idiosyncrasy: Repeated use may lead to tolerance, requiring higher doses, whereas idiosyncratic reactions are abnormal, unpredictable responses to a drug.
• Drug Interactions: The presence of other medications can lead to synergistic, additive, or antagonistic effects, altering the required dosage of the primary drug.
• Accumulation: Drugs with long half-lives may accumulate in the body, requiring a reduction in maintenance doses to avoid cumulative toxicity.