Concentrations

PREPARING SOLUTIONS AND REAGENTS

concentrations
Is weight over volume (w\v) relationship, it mean certain weight dissolved in certain volume of solvent.

The amount of a drug in a given volume of blood plasma, measured as the number of micrograms per milliliter.

One way of comparing drug potency is by the concentration at which 50% of the maximum effect is achieved. This is referred to as the 50% effective concentration or EC50. When two drugs are tested in the same individual, the drug with a lower EC50 would be considered more potent

For liquid drugs ,both oral and injectable

concentration is important factor in dosing.

It refers to the amount of active drug(dose in mg) in a given volume vehicle usually a liquid but could be paste. e.g Suspension is 100mg\ml
e,.g ampoule contain 50mg\2ml

concentrations

1%--------------1gm in 100ml
1:100,000--------------1gm in 100,000ml
1:80,000----------------1gm in 80,000ml
2%=2gm of lidocaine in 100ml of solvent


Dose calculation
Dose: is the measured portion of medicine to be taken at one time.

Factors influencing dosage

1- age: children and elderly
2-sex:pregnancy and fetus
3- condition of the patient: resistance ,kidney and liver disease
4-enviromental factors:
5-method of administration:
6- genetic factor:
7-body weight:
8- severity of disease:

Dose calculation in children

1-Youngs rule:
a Child dose= age of child(year)x average adult dose
age of child(year)+12
CHILD FROM 1-12 years

Dose calculation in children

2- Clarks rule:
Child dose= weight of child(pound)x adult dose
150 pound


Dose calculation in children
3-For infant less than one year old use
FRIEDS RULE
child dose= age in months x adult dose
150 pound

Chemical Solutions (aqueous = water is the solvent)

• DEFINITIONS:
• SOLUTES -- substances that are dissolved
• SOLVENTS -- substance in which solutes are dissolved (usually water)
• AMOUNT -- how much

Goals

Make solutions
Dilute solutions
Convert between different concentrations of solutions

Facts of Life

• 1g = 1000mg = 1,000,000µg
• 1L = 1000mL = 1,000,000 μL


Facts of life (cont’d)
Concentration means: amount of solute in a volume of solution

Expressed in many ways:

1. percent
2. mg/ mL
3. molar
4. “X” solution

Each star represents 1 mg of NaCl.

What is the total amount of NaCl in the tube? _____
What is the concentration of NaCl in the tube (in mg/mL)? _____

8 mL

5 mg = ?
8 mL 1 mL

? = 0.63 mg, so the concentration is

0.63 mg/mL


Percent Solutions
Per means “for every one”
Cent means 100

Example: a 5% sugar solution has

5 grams of sugar for 100ml of solution, or

Make 250 mL of a 3% starch solution

3 g / 100 ml = 3 g / 100 mL because density of water is 1 g / mL

Set up a ratio:

3 g / 100 mL = ?g / 250 mL

Use 7.5 g of starch and bring to a volume of (BTV) 250 mL with distilled water

5 mg/mL has 5 milligrams of solute in
one milliliter of solution
mg / mL Solutions