Final answer:
Most drugs are given orally as tablets or capsules due to convenience, safety, and the suitability for long-term treatment, although some drugs are designed for local treatment within the GI tract or as topical applications. When oral administration is not feasible, alternative, often parenteral, routes are chosen. Dosage determination is a critical aspect that considers safety and therapeutic effectiveness.
Step-by-step explanation:
Most drugs are given orally as tablets or capsules because this mode of administration is generally more convenient for patients, allowing them to take their medication at home. In comparison to parenteral routes such as intravenous or intramuscular injections, oral administration is less invasive and better suited for long-term treatment. Furthermore, it avoids the risks associated with injections, such as infections and requires less medical supervision.
Some drugs, however, are not readily absorbed through the gastrointestinal (GI) tract and may then be designed to treat local conditions within it, such as tapeworms or for bowel decontamination. Drugs with poor systemic absorption might also be produced as topical preparations for skin conditions. In the case of severe illness where oral ingestion is not possible, alternative routes like intravenous administration are used in healthcare settings, which can achieve higher plasma levels more rapidly when necessary.
The dosage of a drug must be carefully determined to ensure the optimal therapeutic levels are reached without causing toxicity. Various properties, such as solubility and permeability, affect a drug's ability to be effectively absorbed via the oral route. Factors to consider when determining dosage include the patient's age, mass, and organ function, particularly the liver and kidneys which are involved in drug metabolism and clearance.