Doses of some drugs may need to be adjusted if a patient is severely overweight, severely underweight, or suffers from renal (kidney) or hepatic (liver) impairment.
However, these pharmacokinetic differences are outside of the scope of this module.
Want some more practice? Try the questions headed “injected medications”; “medications used in critical care”; “oral medications”; and “paediatric & neonatal medications” located here:
http://wps.pearsoned.com.au/au_hss_bullock_fundpharma_5/56/14450/3699402.cw/index.html
Different nomograms are available for adult, adolescent, and paediatric patients. Make sure you’re using the correct one!
Dose calculation is just a practical application of your basic maths skills.
The dose of a drug is the amount taken by a patient for the intended therapeutic effect
Doses can be stated in many different ways, depending on the patient, the formulation, and the route of administration. Generally, in healthy adults, doses are calculated based on patient weight. In children, the patient’s age and weight will generally be considered. There are some exceptions to these cases, however - some more potent medications (especially chemotherapeutic agents) will use body surface area instead of weight or age, as this is more accurate.
Doses in pharmacy and medical references are most commonly expressed in the form of quantity of drug (usually in milligrams) per unit weight of the patient (usually kilograms).
The expression "migs per kigs" is often heard on medical dramas on T.V., however the proper units is in fact mg/kg (milligrams of drug / kg of patient body mass)
After birth, different organ systems mature at different rates. As a result, children have different body compositions and organ function compared to adults, and so may require different doses. Also, children generally weigh less than a typical adult. Therefore, children’s doses are sometimes based not only on weight, but also on their age (which should identify their stage of physical development).
Oftentimes cancer chemotherapy doses will be stated based on dose per unit body surface area (BSA). This measure is sometimes also used in paediatric patients. Nomograms are available to convert between height, weight and BSA. Your APF also contains a table which gives average BSA based on a child’s weight and age.
https://emedia.rmit.edu.au/drugcalcs/?q=nomogram
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