1. Dose measurement Lecturer: dr. Asmaa abdelaziz Mohamed
Faculty of pharamcay
Ibn hayan University 1

2. dose
Dose: is the quantitative amount administered or taken by patient for the intended medicinal effect. Single dose: The amount taken at one time. Daily dose: The amount taken during the course of therapy. Divided dose: two or more times per day. 2

3. Dosage regimen
Dosage regimen: the schedule of dosing, e.g. four times per day for 10 days. Drugs doses vary among drugs; some of them have small doses and other have large doses. The dose of a drug for a particular patient may be determined on the basis of the patient’s age, weight, body surface area, general physical health, liver and kidney function (because drug metabolism and elimination occur in these two organs) and the severity of the illness. 3

4. MEC & MTC
minimum effective concentration (MEC): The minimum concentration expected to produce pharmacological activity the minimum toxic concentration (MTC):The level of serum concentration that begins to produce toxic effects is referred to as or maximum safe concentration (MSC) of the drug. Ideally, appropriate drug dosage should result in serum drug concentration that is above the MEC and less than MTC 4

5. CURVE * 5

6. ROUTE OF ADMINSTRATION6

7. Dose measurements
In the institutional settings, doses are measured and administered by professional personnel. A variety of measuring devise may be use including calibrated cups for oral liquid and syringes and intravenous sets for parenteral medication. In the home setting the adult patient or child parents generally measures and administered medication. They use household terms such as teaspoon and tablespoon. In calculating doses, pharmacist and physician accept a capacity of 5mL for the teaspoonful, and 15mL for the tablespoonful. It should be noted that the capacity of household teaspoons may vary from 3-7 mL and those of tablespoons may vary from mL. The following factors affecting dose measurements of liquid drugs: viscosity, surface tension as well as the technique of the person measuring the liquid can influence the actual volume held by household spoon. 7

8. *The drops as unit of measures
the drop is used as a measure for small volume of liquid medication. A drop does not represent a definite quantity, because drops of different liquid vary greatly. The official dropper is calibrated to deliver approximately 20 drops of water per mL. It should be kept in mind that few medical liquid have the same surface and flow characteristics as water and therefore the size of drops varies from one liquid to another. 8

9. example
A physician asked a pharmacist to calculate the dose of cough syrup so that it may be safely administered dropwise to a child. The cough syrup contains the active ingredient, Dextromethorphan 30 mg/15mL in a 120 mL bottle. Based on the child weight, the pharmacist determines the dose of dextromethorphan to be 1.5 mg for the child. The medicine dropper to be dispensed with the medication is calibrated by the pharmacist and shown to deliver 20 drops of the cough syrup per one mL. Calculate the dose, in drops, for the child.
Solution:
30 mg mL X
X = 0.75mL
20 drop mL
X mL
X = 15 drops, answer. 9

10. General Dose Calculation
Number of doses = Total amount / size of dose.
Example: If the dose of a drug is 200 mg, how many doses are contained in 10 g?
10 g = mg
10 000/200= 50 dose
Example: How many teaspoonfuls would be prescribed in each dose of an elixir if 180 mL contained 18 doses?
180/18= 10 mL = 2 teaspoonfuls.

11. Example
Example: How many drops would be prescribed in each dose of a liquid medicine if 15 mL contained 60 doses? The dispensing dropper calibrates 32 drops/mL.
15 mL dose
X dose
X = 0.25 mL
32 drop mL
X mL
X = 8 drops.

12. Some meanings
Fixed dose combination products Many medical products are available containing two or more therapeutic agents in fixed dose. The advantages of this combination are: more convenient, enhance patient’s compliance, less expensive and act as synergistic agents. While the disadvantage: inflexibility in dosing. Splitting tablets A number of tablets are scored or grooved to allow braking into approximately equal pieces. This allows dosage flexibility, reduce the cost of treatment and enables the patient to take a product at a strength that is not otherwise available.

13. Parameters of Dose Calculation
For certain patients, the dose of drugs is determined on the basis of specific patient’s parameters. These parameters include age, weight, body surface area and nutritional status. Among patients requiring individualize dose are: Neonates and pediatric patients. Elderly patients. Any patient (whatever his age) with compromised liver and/or kidney function. Critically ill patients. Patients treated with chemotherapeutic agents.

14. Pediatric patients
It’s the branch of medicine that deals with disease in children from birth through adolescence. Because of the rapid variation in body development in children, the pediatric group is further classified as follow: 1- Premature baby: if he born at less than 37 weeks gestation 2- Neonate (newborn): from birth - 1 month. 3- Infant: 1 month - 1 year 4- Early childhood: 1-5 years 5- Late childhood: 5-12 years 6- Adolescence: years

15. Factors affecting the dose of drug in pediatric patients
1- child age
2- weight
3- overall health status
4- The function of liver and kidney.
In neonates, the liver and kidney functions are under development. Renal function, for example, develops over the span of the first 2 years of life. So we have to be very careful when the antimicrobial and other drugs which are determined by the kidney. This fact is very important because most of the drugs used in children are antimicrobial agents which are eliminated primarily by the kidney. If drugs elimination is not probably considered, drugs accumulation in the body could occur, leading to drug overdose and toxicity. That is why the use of pharmacokinetics data (rate of drug absorption and elimination) together with the patient’s response should be checked.

16. Geriatric Patients
Geriatric medicine is the field that deals with the management of illness in the elderly patients. Most physiologic functions peak before age 30 years, with subsequent gradual linear decline. Kidney function is a major consideration in drug dosing in the elderly because reduced function results in reduced drug elimination. Renal blood flow diminishes nearly 1% per year after age 30, making the decline in most persons 60 to 70 years of age is about 30% to 40%, a value that is even greater in older persons.

17. Special Considerations in Dose Determinations for Elderly Patients
Dose determinations for elderly patients require consideration of the following:
Therapy is often initiated with a lower-than- adult dose.
Dose adjustment based on the therapeutic response.
The patient’s physical condition may determine the drug dose and the route of administration employed.
The dose may be determined on the patient’s weight, body surface area, health and disease status.
Concomitant drug therapy may affect drug/dose effectiveness.
A drug’s dose may produce undesired adverse effects and may affect patient compliance.
Complex dosage regimens of multiple drug therapy may affect patient compliance

18. Thank you