Calculation of Medication Doses Flashcards
CHAPTER 8
BSA
Body Surface Area
CrCl
Creatine Clearance
IBW
Ideal Body Weight
PRN
Pro re nata
Play an integral role within the pharmacy profession and are an essential fundamental component of professional degree knowledge.
Pharmacy calculations
Quantitative amount administered or taken by a patient for the intended medicine effect.
Dose
Types of doses (4)
- Single dose
- Daily dose or Total dose
- Divided dose
- Dosage regimen
The amount of dose taken at one time
Single dose
The amount of dose taken during the course of therapy. A daily dose may be subdivided and taken in divided doses
Daily dose or Total dose
Two or more times per day depending on the characteristics of the drug and illness
Divided dose
The schedule of dosing (4x a day for 10 days)
Dosage regimen
The dose of a drug is based on its ___ and ___ , its ___ and ___ , the ___ used, the ___ and ___ .
biochemical and pharmacologic activity; physical and chemical properties; dosage form, route of administration, and various patient factors
Hutton (2009) devised five-step approach in dealing with drug calculations:
- Extract the relevant information from the prescription
- Check if the available medicine is in the same units as the prescribed dose
- For the dose prescribed, estimate whether you need more or less than the medicine on hand
- Calculate the dose to be given
- Check that your answer is around the estimate amount and is a sensible amount to be given by the prescribed route.
Body weight unit
mg/kg
Body surface area unit
mg/m2
Using ___ estimate is more accurate, since any physical phenomena are more closely related to it.
Body Surface Area (BSA)
BSA is a better indicator of ___ than body weight because it is less affected by abnormal adipose mass.
metabolic mass
BSA can be applied as follows:
___ is usually divided by the BSA to gain an appreciation of the true required glomerular filtration rate (GFR)
Renal clearance
BSA can be applied as follows:
___ is often dosed according to the patient’s BSA
Chemotherapy
BSA can be applied as follows:
___ can also be expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement
Glucocorticoid dosing
To find the BSA of a patient, first measure the patient’s ___ and ___ . Then, the BSA can be calculated using a formula or ___
height and weight; nomograms
A nomogram typically has three columns:
- Height based in both centimeters and inches
- Body surface area in m2
- Weight based in both kilograms and pounds
To use a nomogram, the height and weight of the patient are marked on the nomogram and then a straight line is drawn connecting the two values. The BSA for that patient is found where the line ___ the BSA column.
intersects
Most patient the ___ is the weight to be considered for dosing drugs.
Actual body weight (ABW) or Total body weight (TBW)
Obese
BMI greater than 30
In the case of obese patients, they may receive an ___ . The reason for this is that ___ plays virtually no part in metabolism (including drug clearance). Using ___ may be more appropriate.
artificially high dose;
fat tissues;
Ideal Body Weight