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Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

Reconstitution and Safe Medication Administration Introduction In this module, you will learn the details of reconstitution, a process that generates liquid medication solutions from dry, concentrated forms of drugs. This technique is necessary for certain medications prior to delivery. You will then become acquainted with the principles of safe and effective medication delivery. These have been implemented as a means of reducing errors in patient care. Some of these concepts have been emphasized in previous modules, and will be summarized here as the six rights of safe medication administration.

Overview x x x x x

Process of Reconstitution Reconstitution of Medication with Multiple Strengths Storage of Reconstituted Solutions Medication Errors Six Rights of Safe Medication Administration

Module Outcomes y Identify pertinent information required to reconstitute powdered medication into a solution. y Perform reconstitution calculations appropriately when multiple directions for reconstitution are given. y Perform dosage calculations using a reconstituted medication solution. y Identify key information to be recorded on multiple-use vials of reconstituted solutions. y Recognize common sources of preventable medication errors. y Identify and apply methods of medication delivery designed to promote sound practice. y Use the six rights of medication administration to verify that a dosage is safe.

Reconstitution of Medications Many medications, including antibiotics and biopharmaceuticals, are unstable in the form of a solution. They either quickly degrade and lose potency, or require costly means of transportation and storage to retain their viability. These drugs are often manufactured and delivered to medical units in vials containing a concentrated form of powdered medication. Before delivering these drugs, a nurse must reconstitute them by adding liquid into the vial, forming a medication solution. Once reconstituted, these

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

solutions begin to decay and are only effective for a limited number of hours or weeks, depending on the drug.

Reconstitution of Medications Examples Here is an everyday example of reconstitution. Instant coffee grinds + Hot water → Coffee The reconstitution of concentrated medications is exactly analogous to this process. Powdered medication (solute) + Diluent (solvent) → Medication Solution (solution) In this context, the liquid added to a vial of powdered medication is referred to as the diluent. When preparing coffee, some prefer a stronger brew and add more coffee grinds or less water than recommended on the label. However, when reconstituting medications, this must be avoided. Vials of concentrated medication list detailed instructions for their reconstitution and should be followed carefully to prevent medication errors. Up until now, we have been working with drugs that are already in the form of a solution. They have a certain amount active ingredient (grams), dissolved in a volume (millilitres) of fluid. This yields a medication solution with a known concentration (grams per millilitre). Reconstitution is the process of combining these active ingredients with the solvent, generating a solution. The instructions for a particular medication are listed on the drug label, and include the following. 1) The volume of diluent to be added This volume should be carefully measured using a syringe. It may not be the same as the resulting volume of the solution. 2) The type of diluent to use. Common diluents include: x Sterile or distilled water: Water in which any microorganisms have been killed or removed by means of radiation, heat or distillation (condensation of water vapour). x Normal saline – NS or N/S: A 0.9% w/v solution of NaCl (salt) in water. x D5W: A 5% solution of dextrose in water. Dextrose is a form of glucose (sugar). x Bacteriostatic water: A sterile solution of water containing benzyl alcohol as a preservative. These solutions withstand contamination and remain sterile even after multiple uses. x Tap water: Generally safe to use for oral delivery. Parenteral medications should not be reconstituted using tap water. 3) The resulting volume Sometimes indicated on the mediation label. While somewhat useful, this value is irrelevant to dosage calculations. The resulting volume may be greater than the volume of diluent added.

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

4) The resulting concentration Always indicated on the medication label. Nurses are never required to independently calculate this value. The concentration is essential in performing dosage calculations. 5) How long the reconstituted solution retains its potency Ranges from hours to weeks. This is often coupled with storage instructions. Solutions that are refrigerated generally last longer than those stored at room temperature. When adding diluent to a concentrated drug form, the medication may occupy some space and contribute to the total volume. This is referred to as displacement, and it occurs is in the reconstitution of penicillin, among other drugs. For instance, adding 1.8 mL of diluent to a powdered drug may result in a total volume of 2 mL. In other cases, the resulting volume remains unchanged. The details of displacement involve complex molecular and ionic interactions, and are difficult to predict. Because of this irregularity, it is impossible to determine the concentration of a solution based on drug mass and diluent volume alone. Nurses must instead rely on the resulting concentration explicitly stated on the medication label.

Reconstitution of Medications Questions Most drugs that require reconstitution simply involve following a set of instructions. These are either listed on the medication label itself or are printed on an insert included with the vial.

a) b) c) d) e)

What is the strength of this vial before reconstitution? What type of diluent should be used? How much diluent should be used? What is the resulting volume after reconstitution? What is the concentration after reconstitution?

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

f) How should the reconstituted solution be stored? g) If the physician order 315 mg of Kefzol, what volume of medication will you administer? h) Validate your answer. Answers: a) b) c) d)

500 mg Sterile Water or 0.9% Sodium Chloride (0.9% sodium chloride is normal saline (N/S) 3 mL 2.2 mL (Due to displacement, the resulting volume is greater than the volume of diluent added.) e) 225 mg per mL. The solution's concentration is simply read off of the label. A common error is to calculate the strength as 500 mg ÷ 2 mL = 250 mg/mL. In fact, using 2.2 mL as the volume here also yields an incorrect concentration. Always use the concentration stated on the label. f) Store in a refrigerator. 315 mg g) Order: 1 225 mg

Concentration: 1 mL 1 mL 315 mg = 1.4 𝑚𝐿 × 225 mg 1 h) Validation: 225 mg 315 mg = 1.4 mL 1 mL 225 = 225

Reconstitution of Medications Example NSN 6505-01-227-3570 For I.V. or I.M. use. Important: This vial is under reduced pressure. Addition of diluent generates a positive pressure. Before reconstituting. See Instructions for Reconstitution. Each vial contains ceftazidime pentahydrate equivalent to 1 gram ceftazidime and 118 mg of sodium carbonate. (Sodium content is approximately 54 mg or 2.3 mEq.) Usual Adult Dose: 1 gram every 8 to 12 hours. See accompanying prescribing information for reconstitution. Dosage and administration instructions. Before reconstitution: Protect from light and store at 15 to 30C (59 to 86 F). Slight yellowing does not affect potency. Properly reconstituted solutions of Taticel are stable for 24 hours at room temperature or 7 days if refrigerated (5C) Caution: Federal law prohibits dispensing without prescription. Jointly manufactured by SmithKline Beecham Pharmaceuticals Philadelphia, PA 19101, and Bristol-Myers Squibb Co., New York, NY 10154 693818-H

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

This vial of ceftazidime has reconstitution instructions printed separately on a package insert. Reconstitution Single Dose Vials: For I.M. Injection, I.V. direct (boius) injection. Or I.V. infusion. Reconstitute with Sterile Water for injection according to the following table. The vacuum may assist entry of the diluent. Shaje Well Table 5 Vial Size Diluent to be added Approx. Avail. Volume Approx. Avg. Concertration Intramuscular or Intravenous Direct (bolus) Injection 1 gram 3.0 ml. 3.6 ml. 280 mg./ml Intravenous Infusion 1 gram 10 ml. 10.6 ml. 95 mg./ml. 2 gram 10 ml. 11.2 ml. 180 mg./ml/ Withdraw the total volume of solution into the syringe (the pressure in the vial may aid withdrawal) The withdrawn solution may contain some bubbles of carbon dioxide. Note: As with the administration of all parenteral products, accumulated gases should be expressed from the syringe immediately before injection of ‘Tazicef’. These solutions of ‘Tazicef’ are stable for 18 hours at room temperature or seven days if refrigerated (5 c). Slight yellowing does not affect potency. For I.V. infusion, dilute reconstituted solution in 50 to 100 ml. of one of the parenteral fluids listed under COMPATIBILITY AND STABILITY. This insert is used for more than one Tazicef product: one has a 1 gram vial, and the other has a 2 gram vial.

Order: Give 500 mg Tazicef IM tid Question: What volume of Tazicef will you administer at each dose? Answer: There are three separate set instructions for reconstitution. The prescribed route of administration and the strength of the Tazicef product on hand determine which instructions to follow. Be careful not to confuse dilution with reconstitution. The term dilution is used when preparing solutions for IV infusion, using much larger volumes of fluid. Order:

500 mg 1

Concentration:

280 mg 1 mL

500 mg 1 mL = 1.8 𝑚𝐿 × 280 mg 1

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

Reconstitution: Multiple Concentrations Reconstitution: Multiple Concentrations Example 1

Bulk Pharmacy Package Read Accompanying Professional Information Usual Dosage 6 to 40 million units daily by intravenous infusion only ml diluent added

Approx. units per ml of solution

75 ml 33 ml 11.5 ml

250,000 u/ml 500,000 u/ml 1,000,000 u/ml

Some drugs have multiple directions for reconstitution. Here, if a large volume of diluent is added (75 mL), then a relatively weak solution results (250 000 units/mL). Conversely, a small volume of diluent (11.5 mL) yields a strong solution (1 000 000 units/mL). The most appropriate concentration to prepare depends on hospital policy, and is based on the prescribed dosage and route of administration. Recall that while intravenous injections can provide large volumes of fluid, subcutaneous and intradermal injections are quite restricted. To illustrate the effect of concentration on dosage volume, consider the following medication order.” [Display the order.] “Any of these three directions for reconstitution may be used, resulting in three different concentrations. Using the order above, the possible dosages are calculated below. x

Adding 75 mL of diluent:

600 000 units 1

×

1 mL 250 000 units

= 2.4 mL

Mathematics for Medication Administration

x

Adding 33 mL of diluent:

x

Adding 11.5 mL of diluent:

Reconstitution and Safe Medication Administration 600 000 units 1

600 000 units 1

×

1 mL 500 000 units

= 1.2 mL

1 mL

× 1 000 000 units = 0.6 mL

It should stand to reason that a small volume of diluent yields a highly concentrated solution; and a highly concentrated solution requires a small volume for injection. For the purposes of this course, the most appropriate dosage to administer is that which is closest to 1 mL. This is an acceptable dosage volume for IV, IM and SC routes (IV doses would likely be further diluted for infusion). In this case, 1.2 mL is closest to a 1 mL dosage, so its associated concentration (500 000 units/mL) is most appropriate. To summarize, given this vial of Pfizerpen and an order for 600 000 units, it would be most appropriate to reconstitute the drug with 33 mL of diluent. This results in a dosage that is close to 1 mL. Fortunately, it not necessary to calculate all possible dosages before performing reconstitution. A shortcut to determine the most appropriate volume of diluent to add is to identify the concentration that is closest to the ordered amount. Here, 600 000 units was ordered. The closest concentration to this value is 500 000 units/mL. Therefore, this is the desired concentration for this prescription. Note that only the instructions available on the label or insert are to be followed. It is not permissible to reconstitute powdered medication using non-standard volumes of diluent. Although it is possible to achieve a dosage of exactly 1 mL, the benefits are insignificant when compared with the potential for committing a computational error.

Reconstitution: Multiple Concentrations Example 2 Read Accompanying Professional Information Recommended Storage in Dry Form. Store below 86°F (30°C) Sterile solution may be kept in refrigerator for one (1) week without significant loss of potency. Caution: Federal law prohibits dispensing without prescription.

NDC 00490520-83 Buffered Pfizerpen® (penicillin G potassium) For Injection Five million units Pfizer Roerig Division of Pfizer Inc, NY, NY 10017

Usual Dosage Average single intramuscular injection: 200, 000-400, 000 units. Intravenous: Additional information about the use of this product intravenously can be found in the package insert. mL diluent added

Units per mL of solution

18.2 mL

250, 000

8.2 mL

500, 000

3.2 mL

1, 000, 000

Buffered with sodium citrate and citric acid to optimum pH. Patient: Room No.: Date Diluted:

Order: Administer 800 000 units penicillin G, IM TID Questions:

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

a) What volume of diluent should be added to the vial for reconstitution? Answer: 3.2 mL. Of the three available concentrations, 1 000 000 units/mL is closest to the ordered amount. This requires adding 3.2 mL of diluent, according to the instructions for reconstitution. b) What volume of penicillin will you administer to give the prescribed dose? Answer: 0.8 mL. With an order for 800 000 units, and a resulting concentration of 1 000 000 units/mL, this problem is no different than any other dosage calculation. 800 000 units 1 mL = 0.8 mL × 1 000 000 units 1 A common error is to interpret this concentration as 1 000 000 units per 3.2 mL. Recall that the concentration is always stated explicitly on the label. In this case, the number 1 000 000 is expressed in units/mL.

Add 3.2 mL diluent

Add 8.2 mL diluent

Add 18.2 mL diluent

The 3.2 mL volume is not a component of the concentration; it is merely part of the directions for reconstitution. [Empty vial]: To understand this concept, consider the vial before reconstitution. Initially, the vial only contains dry, concentrated medication. There are 5 000 000 units of penicillin altogether, as indicated on the drug label. [5 mL vial]: After adding 3.2 mL of diluent, a fairly concentrated solution results. In this case, the dissolved drug displaces some volume, resulting in more than 3.2 mL of

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

solution. [show 5 mL indicator] Incidentally, the total volume after reconstitution is 5 mL, though this is not stated on the vial. [10 mL vial]: If instead, 8.2 mL of diluent were added, then 10 mL of solution would result. Again, the total volume here is unnecessary for dosage calculations and is not indicated on the drug label. [20 mL vial]: Finally, adding 18.2 mL of diluent yields a total volume of 20 mL. In each of these three cases, displacement causes the total volume to be greater than expected. It is not possible to predict the resulting volume without physically performing reconstitution. Consequently, it is not possible to determine the concentration of each solution without mixing in the various volumes of diluent. Fortunately, this work has been done for you, and is summarized on the medication label. [5 mL vial] Here, the vial contains a total of 5 000 000 units of penicillin in 5 mL of 5 000 000 units solution. The concentration is , which reduces to 1 000 000 units/mL. 5 mL

[10 mL vial] This vial also has a total of 5 000 000 units, but this is contained in 10 mL of 5 000 000 units solution. The concentration is , which reduces to 500 000 units/mL. 10 mL

[20 mL vial] Finally, the 20 mL vial also contains 5 000 000 units of penicillin but is 5 000 000 units diluted in 20 mL of solution. The concentration is , which reduces to 250.000 20 mL units/mL. You can now appreciate how each of the three concentrations was determined. This information is neatly summarized on the drug label and does not need to be calculated separately.

Reconstitution: Labelling Vials Some medications for reconstitution are packaged in single-dose vials. Typically, most of the medication is used in one dose, and the remainder is discarded. There are also multiple-dose vials that contain more than one standard dose of medication. Once a volume is withdrawn for injection, the remaining solution can be stored for later use. In doing so, the following details must be recorded on the vial: x x x x x

Concentration Date and time of preparation Date and time of expiration Storage instructions Nurse’s initials

Note: The concentration is especially critical when more than one set of reconstitution instructions is listed on the label.

Types of Medication Errors Several bodies of research have shown that medication errors occur at an alarming rate. The Canadian Medical Association Journal (2004) estimates that across Canada,

Mathematics for Medication Administration

Reconstitution and Safe Medication Administration

medication errors contribute to between 9 000 and 24 000 preventable fatalities each year. This has prompted extensive research into the causes of such errors, and several preventive measures have been implemented as a result. Medication errors occur in all facets of the healthcare system and include errors: x x x x x x

diagnostics and prescribing drug labelling storage and preparation drug dispensing and administration patient education and monitoring surgical and therapeutic procedures.

For healthcare practitioners, these errors could lead to legal consequences or suspension of licence to practice. More concerning is that patients could be subject to injury, disability or death as a result of malpractice. These errors directly contradict a well-known guiding principle in the practice of medicine: do no harm. This doctrine is deceptively simple, but often misunderstood. Consider an individual with a condition that requires professional attention. He or she visits a hospital to seek therapy. If the condition worsens as a result of this visit, or further injury occurs, then the patient would have been better off without pursuing treatment. Here, the hospit...