Drug Administration Dosage Forms and Routes Quiz

Dosage Form Design and Routes of Administration

• Drugs can be administered using various dosage forms and routes of administration.
• The choice of dosage form and route of administration depends on whether the drug is intended for local or systemic effects.

Local vs Systemic Effects

• Local effects are achieved by direct application of the drug to the desired site of action (e.g., eye, nose, or skin).
• Systemic effects result from the entrance of the drug into the circulatory system and transport to the cellular site of its action.

Drug Absorption and Onset of Action

• Different dosage forms can result in different drug absorption rates and times of onset, peak, and duration of action.
• For example, sublingual, intravenous, and buccal forms of nitroglycerin have extremely rapid onsets of action, while oral and topical forms have slower onsets of action but greater durations of action.

First-Pass Effect

• The bioavailability of a drug is lowest when it undergoes a significant first-pass effect.
• The first-pass effect is calculated as the hepatic extraction ratio, or the fraction of drug metabolized (E).
• The fraction of drug that enters the systemic circulation and is ultimately available to exert its effect is equal to (1 − E).
• Examples of drugs that undergo a significant first-pass effect when administered orally include propranolol, verapamil, and metoprolol.

Compensating for First-Pass Effect

• To compensate for the first-pass effect, manufacturers may consider alternative routes of administration, such as intravenous, intramuscular, or sublingual.
• The dosage must be adjusted accordingly to avoid adverse effects.
• The metabolites themselves may be pharmacologically active or inactive, affecting the dosage required to achieve the desired therapeutic effect.