Medications from Powders and Crystals: Oral and Intramuscular
Objectives
• Determine the best dilution strength to use for multiple-dosage strength vials.
• Calculate doses in milligrams, grams, and milliliters for oral and parenteral routes.
• Reconstitute and measure liquid medications.
Introduction
Preparation of reconstituted medications, mostly antibiotics, from powders and crystals is usually the nurse’s responsibility. The medications are reconstituted by adding a diluent (liquid) recommended by the manufacturer as the vehicle for administration. The shelf life of reconstituted medications is usually short; therefore, careful consideration must be given to how they are stored, the date and time of reconstitution (initialed by the nurse), the expiration date, and the route of administration. This chapter teaches the steps for safely preparing medications from powders and crystals. The measurement of units will be spelled out in the physician’s orders and is used in the problem setups.
Measuring Liquid Medications
When measuring a liquid medication, hold the transparent measuring device at eye level. The curved surface of the liquid is called the meniscus (Figure 6-1). All liquid medication is measured at the meniscus level.
Medications can be measured in a medicine cup and transferred to an oral syringe for ease in administration and accuracy (Figure 6-2).
However, liquid medications can be measured more accurately in a syringe than in a medicine cup (Figure 6-3).
Reconstitution: Medication Labels
Labels for medications that require reconstitution contain information about the amount of diluent to use and the resulting concentration. The important information is as follows:
CLINICAL ALERT
If the vial is a multiple-dose vial, the nurse must note on the label the date, time, amount of diluent used, and his or her initials.
Many solutions are unstable after being reconstituted. Read labels carefully for directions on storing the solution in the refrigerator or in a dark place. There is usually a time limit or expiration date on the vial. It is important to date, label, and initial all reconstituted medications.
WORKSHEET 6A
Answers on page 374
Practice in Reconstituting, Administering, and Measuring Liquid Medications
Show your calculations and proofs in the following problems. Shade in the correct dose on the medicine cup.
1. Ordered: Lorabid 150 mg po bid.
Follow mixing directions on the label.
a. How many total milliliters of water are needed?
b. How many total milligrams of Lorabid are in the bottle?
d. How many doses are in the bottle?
2. Ordered: Dynapen (Dicloxacillin sodium) 150 mg po stat, then 62.5 mg every 6 hours.
a. How many milliliters of water will you add?
b. How many milliliters will you administer?
c. How many doses are remaining after administering the stat dose?
3. Ordered: 500 mg of Vancocin suspension b.i.d. po.
a. How many milligrams are in the bottle?
b. How many milliliters will you administer? Draw the amount you will give on the medicine cup.
4. Ordered: Augmentin suspension 200 mg po q8h.
a. How many milliliters of water will you add?
b. How many total milliliters are in the bottle?
c. How many milliliters of Augmentin will you administer? Draw the amount you will give on the medicine cup.
5. Ordered: Lorabid 400 mg po q12h × 14 days 1 hour ac for pneumonia.
Follow mixing directions on the label.
a. How many total milliliters of water are needed?
b. How many total milligrams of Lorabid are in the bottle?
c. How many milliliters will provide 400 mg? Draw the amount you will give on the medicine cup.
d. How many doses are in the bottle?
6. Ordered: 40 mg Pepcid po four times a day.
a. How many milliliters of diluents will you add?
b. How many total milliliters of Pepcid are in the bottle?
c. How many milliliters will you administer?
d. How many doses are in the bottle?
7. Ordered: Vancocin HCl 300 mg po bid for colitis.
Follow mixing directions on the label.
a. How many milliliters of distilled water are needed?
b. How many total milligrams of Vancocin are in the bottle?
c. How many milliliters of Vancocin HCl will provide 300 mg? Draw the amount you will give on the medicine cup.
8. Ordered: Amoxil (amoxicillin) 500 mg po q8h for endocarditis prophylaxis.
a. How many milliliters of diluent will you add?
b. How many total milligrams are in the bottle?
d. How many doses are in the bottle?
CLINICAL ALERT
For accuracy, read the medication’s level at the meniscus.
9. Ordered: Fluconazole 50 mg po twice a day.
a. How many mL of sterile water will be added to the powder?
b. How many mL will you administer?
c. How many 50 mg doses are in the bottle?
10. Ordered: 200 mg of Biaxin po two times a day.
a. How many mL of water should be added?
b. How many mL will you administer?
c. How many doses are in the bottle?
Reconstituting Medications for Parenteral Use
Reconstituting medications is much like making a cup of soup out of dried soup mix from a package or using freeze-dried coffee crystals to make a cup of coffee. The concept is the same. When a lot of liquid, or diluent, as it is referred to when mixing medications, is used, the soup or coffee becomes weaker. The less liquid or diluent used, the stronger the soup or coffee. For some medications that must be reconstituted, various amounts of diluent or liquid can be added to produce various strengths of the medicine. As an example, if you add 16 oz, or 1 quart, of water to 1 Tbsp of instant coffee, you will have very weak coffee. If you add 8 oz of water to 1 Tbsp of instant coffee, you will have stronger coffee and less total volume. The main point is that the amount of instant coffee remains constant; only the amount of liquid (diluent) changes to make stronger or weaker coffee. Reconstituting medications works in the same manner. There is always a certain amount of powder or crystals in the container before the diluent is added. The drug manufacturer tells you what the displacement factor is. This amount is added to the amount of diluent to give the total number of milliliters. The label on the medication vial states the strength (amount) of medication in the vial. That amount never changes. The only thing that can change is the amount of diluent (liquid) that is added.
Most reconstituted medications come in single-dose vials rather than multiple-dose vials, and various amounts of diluent can be added to make varying strengths of medication.
Types of Diluents
It is important to use the type of diluent described in the directions for reconstitution. The diluents used to reconstitute powders vary based on the chemical properties of the powder. For example, erythromycin must be reconstituted with sterile water. If normal saline (NS) is used, the powder clumps and will not go into solution. The bacteriostatic agent used in bacteriostatic water is benzyl alcohol. If sterile water is used instead of bacteriostatic water, it may cause some products to clump instead of going into solution. The choice of diluent is based on the pH and the physical properties of the product (medication).
Dibasic sodium is added to some powders to correct the final pH of the product.
Lidocaine is added to ease pain during IM administration. The amount of lidocaine added to the medication would not affect vasoconstriction.
CLINICAL ALERT
Always use the diluent recommended for reconstitution.
Diluting Powders or Crystals in Vials
Directions for dissolving medications in vials can be found in the accompanying literature. What will be given is the volume of the powder after it is dissolved in the diluent. For instance, the directions may read: Add 1.4 mL NS to make 2 mL of reconstituted solution. These directions tell the user that the powder takes up to 0.6 mL of space. The displacement factor is 0.6 mL.
1.4 mL + 0.6 mL = 2 mL of medication
Example
Read the medication label to find out how many units, grams, milligrams, or micrograms are in each milliliter of the reconstituted drug.
Begin by adding 2.7 mL of air to the sterile water for injection (diluent) vial, and then invert the vial to withdraw the 2.7 mL of diluent. Add the 2.7 mL of diluent to the oxacillin sodium vial to make 500 mg of medication in 3 mL (Figure 6-4).
Ordered: 250 mg oxacillin sodium IM q6h.
CLINICAL ALERT
When giving intramuscular injections, always aspirate before injecting. If blood is returned, discard the dose.
When medications to be reconstituted are packaged with the diluent attached, the sterility and accuracy of the reconstituted powder are ensured (Figure 6-5). Some medications are reconstituted by the manufacturer and are delivered in prefilled cartridges or syringes (Figure 6-6).
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