7

Reconstitution of Powders and Liquids

OBJECTIVES

• Distinguish routes of drugs for reconstitution.

• Interpret directions for dilution of reconstituted medications.

• Select the appropriate concentration to prepare for the ordered dose.

• Calculate doses for reconstituted medications using DA equations.

• Measure the appropriate dose using a medicine cup and a syringe.

• Identify appropriate notation on reconstituted multidose medication labels.

• Interpret directions for safe storage of reconstituted medications.

• Calculate ratio dilutions for partial-strength solutions.

“Each problem that I solved became a rule which served afterwards to solve other problems.”

—RENE DESCARTES

Essential Prior Knowledge

• Mastery of Chapters 1–6

Essential Equipment

• The mathematics can be mastered without equipment, but eventually supervised clinical laboratory experience with vials, syringes, and powders will be necessary.

Estimated Time To Complete Chapter

• 1-2 hours

Introduction

Campers who have reconstituted dried food and care-givers who have mixed powdered baby formula with water to prepare a bottle have applied the technique of reconstitution of dry products. Some medications are supplied in the form of powders or crystals to which a liquid must be added for reconstitution shortly before use.

The medications are supplied in dry form because the product can be stored for a long time in dry form but becomes unstable and deteriorates in solution within a relatively short time. Such solutions are said to have a “short shelf life.” The equipment used to reconstitute medications must be calibrated for the medicines being dispensed. The capacity of syringes, medicine droppers, and “medication teaspoons” is precise, while that of household equipment varies greatly from spoon to spoon and cup to cup.

ESSENTIAL Vocabulary

Diluent Fluid that makes a mixture less concentrated or viscous. The fluid dilutes the mixture. It is also used to convert a dry form of a substance to a liquid form. For example, water is used to liquefy a dry form of baby formula. When reconstituting medications, read the directions to find out which diluent needs to be used. Water or normal saline (NS) solution is often used to dilute medicines and to liquefy dry, powdered forms of medicines.

Dilution Extent to which the concentration of a mixture is reduced.

Dilution Ratio Special ratio indicating the number of parts of an active ingredient to the number of parts of inactive ingredients in a solution. For example, a 1:4 dilution ratio means that, out of 5 total parts, 1 part is active and 4 parts are inactive. Adding 4 parts water to 1 part powdered milk would provide a dilution ratio of 1:4.

Displacement Volume occupied by a powder when a diluent is added during reconstitution.

Reconstitution Process of combining the dry form of a mixture with a fluid to achieve a usable state. Process of diluting a liquid concentrate to achieve a usable state.

Solution Concentration (Strength) Amount of drug in a quantity of solution expressed as a ratio (e.g., 100 mg per 100 mL, or 1:1) or as a fraction or a percentage (e.g., 12 strength, or 50% solution).

Suspension Liquid in which fine particles are dispersed throughout a fluid, where they are supported by the buoyancy of shaking or stirring. If a suspension is left standing, the solid particles settle. Antibiotics are often supplied as oral suspensions.

SW Sterile water. Sterile water with an antimicrobial agent, such as benzyl alcohol.

Bacteriostatic SW Sterile water and bacteriostatic sterile water cannot be used interchangeably with each other or with tap water. The product label specifies the diluent.

Unit Standardized laboratory measure of the therapeutic strength, as opposed to the weight or volume, of a drug. Often used as a standard of measure for medications that are derived from plants and animals and that have components with variable strengths. Substances, such as hormones and penicillin, that are partially derived from animal and plant sources are easily broken down to an unstable state of diminished effectiveness. The term units is also used to describe metric units of measurement.

Unstable Easily broken down to a state of diminished effectiveness. Breakdown can occur rapidly with reconstituted solutions. Foods, solutions, and certain medications that are unstable, such as reconstituted medications, have a short shelf life. They must be discarded if they are not used in a timely fashion. Refrigeration may extend shelf life. Consult the label.

RAPID PRACTICE 7-1   Vocabulary Review

Estimated completion time: 5 minutes Answers on page 520

Directions: Circle the correct definition for the following.

1. The amount of drug in a quantity of solution expressed as a ratio is called

1. An emulsion

2. The concentration

3. A suspension

4. A diluent

2. The solution used to reconstitute powders and crystals from a dry form of medicine to a liquid form is called

1. An emulsion

2. An elixir

3. A suspension

4. A diluent

3. Solutions that deteriorate rapidly in liquid form are considered to have a short shelf life and are described as:

1. Crystals

2. Unstable

3. Bacteriostatic

4. Diluents

4. The process of combining a liquid with a solid form of medication so that the medication can be used is called

1. Reconstitution

2. Dilution

3. Calibration

4. Concentration

5. Accurate measurement of liquid medications requires which type of equipment?

1. Household teaspoons and tablespoons

2. Equipment with metric calibrations

3. Household droppers and cups

4. A syringe and needle

Reconstituted Medications

Some medicines are very unstable in liquid form. Therefore, they are supplied in a dry form to which an inactive diluent is added just before use. The information about the specific type and amount of diluent to be added to achieve specific concentrations is provided on the label. The nurse selects the amount of diluent that will provide the concentration closest to the dose ordered.

Interpreting orders and reading labels for reconstituted medications

Examine the following order: Augmentin suspension 125 mg tid PO × 5 days. The order includes the form, oral suspension, but does not mention that the drug requires reconstitution or describe how to prepare it. The nurse must read the medication label and insert to determine how to prepare the medication.

 Pharmacists usually reconstitute large volume oral suspensions and relabel with the quantity per dose to be given.

Reading Labels

Directions on the label state the precise amount and type of liquid diluent to add in order to achieve specific dilutions or concentrations of the drug per milliliter. The directions always state conditions and time limits for storage after reconstitution to liquid form. Some products must be discarded immediately, while others may be refrigerated for several hours or days so that they can be used for additional doses.

There is a lot of information on the label, but most of it is self-explanatory once you have read one or two types of labels. Examine the directions on the following label for an oral suspension to be reconstituted:

 The route is oral. This is important to note because there are injectable antibiotics and other drugs with similar names made specifically for intramuscular or intravenous routes.

 The type of diluent is water. Most oral suspension diluents use tap water unless otherwise specified. Pediatric patients and immunocompromised patients may need SW.

 The total amount of diluent to be added is 90 mL, added in two parts: 60 mL for the first mix and 30 mL for the second.

 After reconstitution, the unit drug concentration (unit dose concentration) will be 125 mg per 5 mL water. The total amount of medication will be 100 mL, although only 90 mL of water was added. This discrepancy is due to displacement of liquid by the powder. Both ingredients occupy space. Discard after 10 days.

 Reconstitution of an injectable is illustrated on p. 217.

CLINICAL RELEVANCE

It is critical to communicate the date and time of preparation and the specific concentration of reconstituted solutions to nursing staff on subsequent shifts with a clearly marked added label.

Marking the label for reconstituted medications

The label is marked by the nurse only under the following conditions:

1. The drug label states that the medication may be used more than once after reconstitution.

2. The patient is eligible to receive another dose before the drug must be discarded.

 The label for reconstituted medications must contain the patient’s name, the date and time of preparation, the diluent type and amount added, the concentration per milliliter after dilution, and the nurse’s initials or name, according to agency policy. Discard date and time are added according to agency policy. Refer to the Augmentin label on p. 206 and the reconstituted label below.

EXAMPLES

RECONSTITUTED AUGMENTIN ORAL SUSPENSION BOTTLE

Patient: John B. Doe

01/05/11 1800: 90 mL SW added; 125 mg per 5 mL, JM, RN

Discard date and time^*:

---

^*Check institutional policies for specific agency requirements, especially discard date requirements. Some agencies require that the nurse add the discard date and time for the prepared reconstituted drug to the label. Other agencies prefer that the expiration or discard date and time be redetermined from the reconstitution date and label directions by each nurse administering the medication.

CLINICAL RELEVANCE

 Reconstituted medications for multidose use are the one exception to the rule, “Never give a medication prepared by someone else.”

 The exception may be made only if the label is clearly marked with all the required data.

 Reconstituted medications with labels that are not annotated with all the required data must be discarded to avoid giving an ineffective drug or a spoiled liquid.

Expired Reconstituted Drugs

Single-dose preparations cannot be stored. The remainder must be discarded. Only multidose preparations may be stored and reused according to label directions and hospital policy.

CLINICAL RELEVANCE

Because of the cost and short shelf life of reconstituted medications, it is appropriate that the nurse review the patient’s records and recent orders to be sure that the medication order has not expired before preparing the medication.

RAPID PRACTICE 7-2   Interpreting Labels for Reconstituted Medications

Estimated completion time: 25 minutes Answers on page 520

Directions: Read the labels for the medications and supply the required information. Use brief phrases.

1. 

a. Form and route of medication: __________________________

b. Generic name: __________________________

c. Unit dose concentration after reconstitution (mg per mL)^*: __________________________

d. Unit dose or multidose container: __________________________

e. Total volume in container after reconstitution: __________________________

f. Storage directions: __________________________

2. 

a. Form and route of medication: __________________________

b. Type of diluent to be used: __________________________

c. Total amount of diluent to add to bottle: __________________________

d. Mixing directions: __________________________

e. Unit dose concentration after reconstitution: __________________________

f. Usual adult dose: __________________________

g. Usual child dose: __________________________

h. Unit dose or multidose container: __________________________

i. Expiration, or discard time, after reconstitution: __________________________

 If a slash (/) is used on a drug label or in a drug order, be careful to avoid reading it as the number 1. For example, 5 mg/5 mL may be misread as 5 mg per 15 mL.

3. 

a. Form and route of medication: __________________________

b. Type and amount of diluent to be used: __________________________

c. Total volume in container after reconstitution: __________________________

d. Unit dose concentration after reconstitution: __________________________

e. Storage directions: __________________________

f. Mixing directions after reconstitution: __________________________

g. Discard directions: __________________________

Note that the labels in problems 2 and 3 are for the same medication but contain different unit dose concentrations per 5 mL (1 medication teaspoon). Remember to use special calibrated medication teaspoons and/or droppers if those implements are needed. Use a syringe without a needle for measurement of oral suspensions if the implements are not provided.

4. 

a. Trade name: __________________________

b. Generic name: __________________________

c. Route: __________________________

d. Total amount in vial:

e. Unit dose concentration after reconstitution: __________________________

5. Ordered: Nystatin oral suspension 400,000 units swish and swallow four times daily while awake for an adult with an oral candidiasis (yeast) infection secondary to antibiotic administration.^*

    Directions: Administer ½ of dose each side of the mouth and have patient swish thoroughly and swallow.

a. How many mL will you prepare? __________________________

b. How many mL will you administer each side of the mouth? __________________________

c. Where should the product be stored? __________________________

---

^*milligram(s) per milliliter(s). The unit dose (drug) concentration is a multiple of the usual doses ordered. Note that mL is both the singular and plural abbreviation. Do not write mLs.

^*Problem 5 is an example of a prepared suspension that does not need further dilution.

CLINICAL RELEVANCE

The medications in problems 1 and 5 have already been reconstituted by the pharmacy prior to dispensing. This can reduce errors. Directions for storage and discard need to be emphasized when teaching patients.

RAPID PRACTICE 7-3   Reconstituting, Calculating, and Measuring Oral Doses

Estimated completion time: 30 minutes Answers on page 521

Directions: Read the order and the label, then estimate and calculate the dose using a DA equation. Shade in the medicine cup to the nearest multiple of 5 mL. Indicate the balance of the dose that will be added with the syringe, as shown in problem 1.

1. Ordered cephalexin oral suspension 0.3 g PO q6h for a patient with a respiratory tract infection

a. Total amount and type of diluent to be added: 36 mL (all at once or )

b. Estimate: or less than the dose per 5 mL after reconstitution (circle one)

c. How many mL will you prepare (per dose)? 12 mL to the nearest tenth of a mL?

    DA equation:

d. Evaluation: The answer supports the estimate. The equation is balanced.

Shade in the nearest measurable dose in mL on the medicine cup and draw a vertical line through the calibrated line of the syringe for the remaining mL as applicable.^*

2. Ordered: Augmentin oral susp 0.25 g q8h PO for a patient with otitis media.

a. Amount and type of diluent to be added: __________________________

b. Estimate: more than or less than unit dose after reconstitution? (Circle one.)

c. How many milliliters will you prepare? __________________________

    DA equation:

d. Evaluation: __________________________

Shade in the dose in mL on the medicine cup and draw a vertical line through the calibrated line of the syringe as applicable.

3. Ordered: amoxicillin oral susp 0.2 g PO q8h for a patient with an infection.

a. Estimate: more than or less than unit dose after reconstitution? (Circle one.)

b. How many milliliters will you prepare? __________________________

    DA equation:

c. Evaluation: __________________________

Shade in the dose in mL on the medicine cup and draw a vertical line through the calibrated line of the syringe as applicable.

4. Ordered: fluconazole oral susp 0.03 g PO daily for a patient with oral candidiasis.

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