chapter 8 Flashcards
It is the quantitative amount administered or taken by a patient for the intended medicine effect
dose of a drug
It is the amount taken at one time.
Single dose
It is the amount taken during the course of therapy. A daily dose may be subdivided and taken in divided doses.
Daily dose or Total dose
These are two or more times per day depending on the characteristics of the drug and the illness.
Divided doses
It is the schedule of dosing (i.e., four times per day for 10 days).
Dosage regimen
The dose of a drug si based on its biochemical and pharmacologic activity, its physical and chemical properties, the dosage form used, the route of administration and various patient factors.
The dose of a drug for a particular patient may be determined ni part on the basis of the patients’ age, weight, body surface area, general physical health, liver and kidney functions, and the severity of the illness being treated
He devised a five-step approach in dealing with drug calculations.
Hutton
Some drugs are not chemically stable in solution and so are supplied as dry powders for reconstitution just before use. Many of these are antibiotics, but there is also a range of chemotherapeutic agents used in cancer treatment
An oral antibiotic for reconstitution comes as a powder in a bottle with sufficient space to add the water.
The powder itself wil remain stable for up to ___ when dry. When reconstituted, a shelf life of ____ is normal, depending on whether it is refrigerated or not.
two years
10 to 14 days
1 kg = 2.2 lbs
Certain situations would require to calculate doses based on body weight (mg/kg) or in terms of a patient’s body surface area (mg/m’).
Using body surface area (BSA) estimates is more accurate than using body weight, since many physical phenomena are more closely related to the BSA.
This particularly applies to cytotoxics and other drugs that require an accurate individual dose.
For many clinical purposes, it is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass.
Body Surface Area
It is usually divided by the BSA to gain an appreciation of the true required glomerular filtration rate (GFR).
Renal clearance
It is often dosed according to the patient’s BSA.
Chemotherapy
It can also be expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.
Glucocorticoid dosing
A common method used to identify BSA
Nomogram
A nomogram typically has three columns:
• height based in both centimeters and inches;
• body surface area in m2; and
• weight based in both kilograms and pounds
The formula derived by Mosteller (1987) combines an accurate BS calculation with ease of use and has been validated for both children and adults. This formula can be used on a handheld calculator:
m2 = height (cm) x weight (kg) / 3,600
Take note that for most patients the _____ is the weight to be considered for dosing drugs.
actual (total) body weight (ABW or TBW)
BSA rule:
BSA of child (m2)/1.73 m2 x adult dose
They are generally classified as persons over 60 years of age.
Geriatric patients
Some patients may have geriatric symptoms at 50 years of age or even younger. As we age, our physiologic functions start to decline.
These are major concerns when dosing medications in elderly patients. They both affect the absorption and elimination of medications.
Kidney and liver functions
It may affect drug/dose effectiveness.
Concomitant drug therapy
It is a major consideration in drug dosing in the elderly because its reduced function results in reduced drug elimination.
Kidney function
It 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%,
Renal blood flow
It is derived from metabolism of creatinine 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 the glomerulus
Creatinine
They are classified as persons under the age of 18
Pediatric patients
Age Breakdown of Pediatric Patients
Neonatal - birth to 1 month
Infant - 1 month to 2 years
Child - 2 years to 12 years
Adolescent - 13 years to 17 years
These are medications that are used for cancer.
They are very potent, hazardous chemicals that cause cell death.
Because these agents are so hazardous, dosing them correctly is critical. These medications are normally dosed based on BSA and take into consideration kidney (renal) function
Chemotherapy agents
It is used with more than a single treatment modality included in a patient’s treatment plan (e.g, radiation and chemotherapy) (14). It often include two-agent regimens, three-agent regimens, and four-agent regimens
combination therapy
The major categories of chemotherapeutic agents include:
alkylating agents
antimetabolites
plant alkaloids
antitumor antibiotics
steroid hormones
The major categories of chemotherapeutic agents include:
alkylating agents
antimetabolites
plant alkaloids
antitumor antibiotics
steroid hormones
Chemotherapeutic agents most often are administered orally, by intravenous injection, or by continuous intravenous infusion;
however, other routes of administration are used as required, including intra-arterial (artery), intrathecal (spinal column), or intramuscular injection, or administration to a specific site, such as the lungs (intrapleural), the abdomen (intraperitoneal), the skin (topical), or others
For systemic action, chemotherapeutic agents are usually dosed based either on body weight or body surface area.
