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
Geriatric patients are generally classified as persons over ___ years of age.
60
Some patients may have geriatric symptoms at ___ years of age or even younger.
50
___ and ___ functions are major concerns when dosing medications in elderly patients.
Kidney and liver
Drug determination for elderly patients frequently require consideration of some or all of the following:
Therapy is often initiated with a ___ compared to adult dose
lower dose
Drug determination for elderly patients frequently require consideration of some or all of the following:
___ may be required based on the therapeutic response
Dose adjustments
Drug determination for elderly patients frequently require consideration of some or all of the following:
The patient’s ___ may determine the drug dose and the route of administration applied.
physical conditions
Drug determination for elderly patients frequently require consideration of some or all of the following:
The dose may be determined, in part, on the patient’s ___ , ___ , ___ and ___ , and ___
weight, body surface area, health and disease status, and pharmacokinetic factors
Drug determination for elderly patients frequently require consideration of some or all of the following:
___ may affect drug/dose effectiveness
Concomitant drug therapy
Drug determination for elderly patients frequently require consideration of some or all of the following:
A drug’s dose may produce ___ and may affect patient compliance
undesired adverse effect
Drug determination for elderly patients frequently require consideration of some or all of the following:
___ may affect patient compliance
Complex dosage regimen of multiple drug therapy
___ is a major consideration in drug dosing in the elderly because its reduced function results in drug elimination.
Kidney function
___ diminishes nearly 1% per year after age 30, making the cumulative decline in most persons 60 to 70 years of age about 30% to 40% a value that is even greater in older persons
Renal blood flow
___ is greatly affected by kidney function.
Drug elimination
___ is derived from metabolism of ___ in skeletal muscles and from dietary meat and releases into the circulation at a relatively constant rate with a stable plasma concentration and freely filtered across glomerulus.
Creatinine
Reduced ___ function results in reduced creatinine clearance rate
kidney
___ are classified as persons under the age of 18
Pediatric patient
Pediatric patients should be dosed based on their ___ or ___
weight or BSA
Toxicity also occur at smaller doses. Weight is still the best way to dose when the ___ is unknown. When done by weight, the drug product tells you the dosing guidelines.
BSA
Types of Pediatric Patients: (4)
- Neonatal
- Infant
- Child
- Adolescent
Neonatal
Birth to 1 month
Infant
1 month to 2 years
Child
2 years to 12 years
Adolescent
13 years to 17 years
Formulas to determine a child’s dose: (3)
- Fried’s Rule (For infants up to 2 years old)
- Young’s Rule (For children 2 years and above)
- Clark’s Rule (For 2 years old and older children)
Are very potent, hazardous chemicals that cause cell death.
Chemotherapy agents
Often, ___ is used with more than a single treatment modality included in a patient’s treatment plan (e.g., radiation and chemotherapy). The ___ plans often include: ___ , ___ , and ___
Combination therapy;
Two-agents regimen
Three-agents regimen
Four-agents regimen
Chemotherapeutic agents act by destroying cancer cells through their effects on ___ or function
DNA synthesis
The major categories of chemotherapeutic agents include: (5)
Alkylating agents
Antimetabolites
Plant alkaloids
Antitumor antibiotics
Steroid hormones
Chemotherapeutic agents most often are administered ___ , by ___ , or by ___ ; however, other routes of administration are used as required, including ___ , ___ , or ___ , or administration to a specific site, such as the ___ , the ___ , the ___ , or others.
orally
intravenous injection
continuous intravenous infusion;
intra-arterial (artery)
intrathecal (spinal column)
intramuscular injection;
lungs (intrapleural)
abdomen (intraperitoneal)
skin (topical)
Cancer chemotherapy therapy is unique in the following ways:
- It may include ___ or ___ of well-established drug therapy regimens or protocols, or it may involve the use of investigational drugs as part of a clinical trial.
single or multiple drugs
Cancer chemotherapy therapy is unique in the following ways:
- Combination of drugs may be given by the same or different routes of administration, most often ___ and/or ___
oral; intravenous
Cancer chemotherapy therapy is unique in the following ways:
- The drugs may be administered ___ or ___ on the same or different days during a prescribed treatment cycle.
concomitantly or alternatively
Cancer chemotherapy therapy is unique in the following ways:
- The days of treatment generally follow a prescribed format of written instructions:
D for ___ , followed by the ___ of treatment cycle;
With a dash meaning ___ and a comma for ___
Day/s;
“To”
“And”
Cancer chemotherapy therapy is unique in the following ways:
- The drugs used in combination chemotherapy often fit into a standard drug/dosage regimen identified by ___ or ___ .
abbreviation and acronyms
Cancer chemotherapy therapy is unique in the following ways:
- Treatment for BLADDER CANCER referred to as MVAC consists of ~
Methotrexate + Vinblastine + Doxorubicin (or Actinomycin) + Cisplatin
Cancer chemotherapy therapy is unique in the following ways:
- Treatment for COLORECTAL CANCER called FU/LU consists of ~
Fluorouracil + Leucovorin
Cancer chemotherapy therapy is unique in the following ways:
- Treatment for LUNG CANCER called PC consists of ~
Paclitaxel + Carboplatin
Cancer chemotherapy therapy is unique in the following ways:
- Treatment for OVARIAN CANCER called CHAD consists of ~
Cyclophosphamide + Hexamethylmelamine + Adriamycin + Diamminedichloroplatinum (cisplatin)
Cancer chemotherapy therapy is unique in the following ways:
- In addition to the use of abbreviations for the drug therapy regimens, the drugs themselves are commonly abbreviated in medication orders, such as MTX for ___ , DOX for ___ , VLB for ___ , and CDDP for ___ .
Methotrexate
Doxirubicin
Vinblastine
Cisplatin
Cancer chemotherapy therapy is unique in the following ways:
- For systemic action, chemotherapeutic agents are usually dose based either on ___ or ___ . Often, the drug doses stated in standard regimens must be reduced based on particular patient’s diminished kidney or liver function and, thus, his or her ability to metabolize and eliminate the drug(s) from the body.
body weight or body surface area
Cancer chemotherapy therapy is unique in the following ways:
- For some patients, ___ is used to kill tumor cells.
high-dose chemotherapy
