Reconstitution of Solutions MAT 119 Chapter 12

Parts of Solutions

Terms Solute – a substance to be dissolved or diluted Solvent or Diluent – a substance (liquid) that dissolves another substance to prepare a solution. Solution – the resulting mixture of a solute plus a solvent/diluent

Reconstitution Drug

Parenteral Solution from a Solid Solute Solvent or diluent 4.8 mL sterile water Solid solute Zithromax 500 mg 5 mL reconstituted solution Zithromax 100 mg/mL

Parenteral Solution Reconstitution Procedure (continues) Order: Kefzol 225 mg IM q.6h

Parenteral Solution Reconstitution Procedure (continued) Withdraw 1 mL Kefzol solution for the ordered dosage of 225 mg Make Kefzol 500 mg in 2.2 mL reconstituted solution for Kefzol 225 mg/mL Inject 2 mL air into sterile water diluent vial Withdraw 2 mL sterile water Add 2 mL sterile water to Kefzol 500 mg powder and shake well

Reconstitution Video http://www.youtube.com/watch?v=8ECYuiHFObU

Multiple-Strength Reconstitution Drug

Different IM and IV Reconstitution Instructions

Reconstitution Drug Order (continues) Order: Solu-Medrol 200 mg IV q.6h

Reconstitution Drug Order (continued) Supply: 500 mg vial of powdered Solu-Medrol for IM or IV injection with directions on the left side of the label that state, “Reconstitute with 8 mL Bacteriostatic Water for Injection with Benzyl Alcohol. When reconstituted as directed each 8 mL contains: Methylprednisolone sodium succinate equivalent to 500 mg methylprednisolone (62.5 mg per mL).”

Reconstitution Dosage Calculation (continues) What do we know? First, to fill the order, how much and what type of diluent must you add? The directions state to add 8 mL of bacteriostatic water for injection with benzyl alcohol. Second, what is the supply dosage of the reconstituted Solu-Medrol? When adding 8 mL of diluent, the supply dosage is 62.5 mg/mL.

Reconstitution Dosage Calculation (continues) Third, what is the resulting total volume of this reconstituted solution? The total volume is 8 mL. You know this because 62.5 mg/mL × 8 mL = 500 mg. Finally, how many full doses of Solu-Medrol are available in this vial? The vial contains 500 mg and the order is for 200 mg. There are two full doses in the vial.

Reconstitution Dosage Calculation (continued) This means that you have available a vial of 500 mg of Solu-Medrol to which you will add 8 mL of diluent. The final yield of the solution is 62.5 mg per mL, which is your supply dosage. Calculate one dose. Step 1. Convert No conversion is necessary Order: Solu-Medrol 200 mg IV q.6h Supply: 62.5 mg/mL

Reconstitution Dosage Calculation (continued) Step 2. Think You want to give more than 1 mL. In fact, you want to give more than three times 1 mL. Step 3. Calculate 62.5 mg = 200 mg 1 mL X given intravenously every 6 hours

Problem The physician ordered Kefzol 265 mg IM q8h. The directions on the label state: “For IM use, add 2.5 mL of sterile water for injection and shake well. The resulting solution has an approximate volume of 3 mL yielding a strength of 300 mg/mL.” How many mL will you administer to the patient?

Answer Ordered: Kefzol 265 mg IM q8h The reconstituted solution now has a concentration of 300 mg/1 mL. Desired 265 mg X 1 mL = 0.883 mL = 0.88 Have on hand 300 mg Ratio/Proportion: 300 mg = 265 mg = 0.88 mL 1 ml X mL

The prescriber ordered Cefotan (cefotetan disodium) 1500 mg IM q 12h. How many milliliters of this antibiotic would you give the patient?

Problem Prescriber order: penicillin G 250,000 units IM daily Directions on the label: Add 9.6 mL diluent = 100,000 units/mL The correct dose based on the doctor's order and the directions on the label is ____ mL. What size syringe? What size needle? 3 mL syringe 1 – 1 1/2 inch

Problem Doctor's order: nafcillin 1 g IM Directions on the label: Add 8 mL diluent = 500 mg/mL The correct dose based on the doctor's order and the directions on the label is ____. What size syringe? What size needle? 3 mL syringe 1 – 1 1/2 inch needle

Problem Ordered: Rocephine (ceftriaxone) 125 mg IM stat. The package insert states that when “1.8 mL of diluent is added to a 500 mg vial, 1 mL of solution contains approximately 250 mg of cefriaxone.” How many milliliters will contain the prescribed dose? What size syringe? What size needle? 1 mL syringe Change needle size from 5/8 in to 1 to 1 1/2 in

Math Tips The diluent is used to dissolve the powdered medicine – becomes reconstituted. Once you use the diluent, it is no longer part of the problem – It is never part of the equation to solve for amount of medication to give. USE IT AND LOSE IT

Math Tip When given the option of diluents in IM reconstitution, choose the amount <3 mL. Question may ask, what is the appropriate amount for an IM injection. If a 1 mL syringe is chosen, the needle must be changed from the 1/2 – 5/8 inch to 1 to 1/2 inch needle.

Solution Strength When a fraction expresses the strength of a solution made from a liquid concentrate: The numerator of the fraction is the number of parts of solute. The denominator of the fraction is the total number of parts of total solution. The difference between the denominator (final solution) and the numerator (parts of solute) is the number of parts of solvent. Numerator = number of parts of SOLUTE . Denominator = total number of parts of SOLUTION Solution – Solute = Solvent

Solution Strength (continued) Example: strength nutritional formula 1 part concentrate (solute) 3 parts of total solution 3 – 1 = 2 parts solvent (water)

Calculating Solutions To prepare solutions: apply ratio-proportion to find the amount of solute: Quantity of desired solution – Amount of solute = Amount of solvent

Solution Calculation Example: Suppose a physician orders a patient’s wound irrigated with strength hydrogen peroxide and normal saline solution q4h while awake. You will need 60 mL per irrigation and will do 3 irrigations during your 12 hour shift. You will need to prepare 60 mL × 3 irrigations = 180 mL total solution. How much stock hydrogen peroxide and normal saline will you need?

Solution Calculation (continued) Step 1. Convert No conversion is necessary. Step 2. Think You want to make strength, which means 2 parts solute (concentrated hydrogen peroxide) to 3 total parts solution. The amount of solvent is 3 – 2 = 1 part saline. Because you need 180 mL of solution, you estimate that you will need of it as solute (120 mL) and of it as solvent (60 mL).

Solution Calculation (continued) Step 3. Calculate (solute) (total solution needed) Now, 180 mL – 120 mL of the solute (hydrogen peroxide) = 60 mL of solvent