Medication Dosing and Administration

Calculation of Doses

• Objectives: Differentiate dose types, describe drug administration routes and dosage forms, calculate doses using household measures, determine medication quantities for a prescribed period, consider factors for pediatric and elderly patients, calculate doses based on age, weight, and body surface area, use dosing tables and nomograms, and calculate doses for single and combination chemotherapy.

• Dose: The quantitative amount of a drug administered or taken for the intended medicinal effect. It can be a single dose (amount taken at one time), daily dose, or total dose (amount taken through therapy). Daily doses can be divided and taken multiple times a day, depending on the drug and condition.

• Dosage Regimen: A schedule for administering doses (e.g., four times a day for ten days).

• Minimum Dose: The lower limit essential for a therapeutic response.

• Maximum Dose: The upper limit tolerated by an average individual.

• Factors Affecting Dose & Action: Age, weight, gender, disease severity, health/nutrition, pathological state, tolerance, simultaneous drug administration, timing/frequency of administration, route, idiosyncrasy (unusual reaction), and allergy.

• General Dose Calculation: Number of doses = (Total quantity)/(Size of dose). Ensure units of weight or volume are consistent.

• Example Calculations (Number of Doses): If a 10g dose is 200 mg each, then there are 50 doses. Likewise, 1 pint (473 mL) of medicine with a 15 mL tablespoon dose, results in approximately 31 doses.

• Example Calculations (Size of a Dose): If 180 mL of medicine contains 18 doses, then each dose is 10 mL (approximately 2 teaspoonfuls).

• Example Calculations (Drops/mL): If 15 mL medication contains 60 doses, and the dropper calibrates at 32 drops/mL, then each dose is 8 drops.

• Example Calculations (Total Quantity): If 2 tablespoonfuls (30 mL) medicine is taken twice daily for 8 days, the total quantity is 480 mL.

• Example Calculation (Tablet Splitting): If a 20mg tablet is split in half, and the two halves differ by 1.5 mg, each half tablet would contain approximately 10.75 mg and 9.25 mg, respectively.

Drug Dosage Based on Age

• Young's Rule: Dose for a child = (Age of child / (Age of child + 12)) × Adult dose.

• Cowling's Rule: Dose for a child = (Age of child / 24) × Adult dose.

• Fried's Rule: Dose for an infant = (Age of infant in months / 150) × Adult dose.

• Clark's Rule: Dose for a child = (Weight of child in lbs / 150) × Adult dose.

• Note: 150 is typically an average adult weight, and values may vary slightly depending on the source.

Drug Dosage Based on Body Weight

• Equation: Patient's dose (mg) = Patient's weight (kg) × Drug dose (mg/kg).

• Example Calculations (Dose Based on Weight): To determine the appropriate dose of chlorambucil for a 154-pound patient, given the 150mcg/kg dose, follow the given calculations in the provided text.

Drug Dosages Based on Body Surface Area (BSA)

• BSA Method: Commonly used for cancer patients receiving chemotherapy and pediatric patients (excluding neonates). It considers factors such as age, biochemical, physiologic, functional, pathologic, and immunologic factors.

• Average Adult BSA: Generally considered 1.73 m².

• BSA Equation: Patient's dose = (Patient's BSA in m² / 1.73 m²) × Drug dose (mg).

• Example Calculations (BSA): Given a 100 mg adult dose, a child with a BSA of 0.83 m² should receive approximately 48 mg.

Nomograms

• Nomogram Use: A graphical tool that determines BSA based on weight and height.

• Nomogram Procedure: Connect the patient's height and weight on the nomogram with a straight line; the intersection with the central column indicates BSA.

• Example Calculations (Nomogram): The provided nomogram allows for visual determination of BSA values based on weight and height data.

Additional Information

• Specific Examples (various ages/conditions): The presented text contains examples of dosage calculations based on age, weight, and BSA.
• Important Considerations: Always check that the units of measurement are consistent throughout any dose calculation to prevent inaccuracies (e.g., convert pounds to kilograms for weight-based calculations).

This quiz covers the essentials of medication dosing and administration, including different dose types, routes, and dosage forms. You'll learn how to calculate doses for various populations, including pediatric and elderly patients, using practical tools like dosing tables and nomograms.