Preparation of two medications in one syringe depends on how the medication is supplied. When using two multidose vials, air is injected into both vials before withdrawing the first medication, to prevent the accidental injection of medication into the second vial. When using a single-dose vial and a multidose vial, air is injected into the multidose vial and the medication in the multidose vial is drawn into the syringe first. This prevents the contents of the multidose vial from being contaminated with the medication in the single-dose vial. The CDC recommends that medications packaged as multiuse vials be assigned to a single patient whenever possible (CDC, 2019). In addition, it is recommended that the top of the vial be cleaned before each entry, and that a new sterile needle and syringe are used before each entry (CDC, 2019).

When considering mixing two medications in one syringe, you must ensure that the two drugs are compatible. Be aware of drug incompatibilities when preparing medications in one syringe. Certain medications are incompatible with other drugs in the same syringe. Other drugs have limited compatibility and should be administered within 15 minutes of preparation. Mixing more than two drugs in one syringe is not recommended (Taylor et al., 2023). If it must be done, contact the pharmacist to determine the compatibility of the three drugs, as well as the compatibility of their pH values and the preservatives that may be present in each drug. A drug-compatibility table should be available to nurses who are preparing medications.

Insulin, with many types available for use, is an example of a medication that may be combined together in one syringe for injection. Insulins vary in their onset and duration of action and are classified as rapid acting, short acting, intermediate acting, and long acting (Frandsen & Pennington, 2021). Before administering any insulin, be aware of the onset time, peak, and duration of effects, and ensure that proper food is available. Be aware that some insulins, such as glargine and detemir, cannot be mixed with other insulins. Refer to a drug reference for a listing of the different types of insulin and action specific to each type.

Insulin is used as the sample medication in the steps outlined below for mixing two medications in one syringe. Insulin is typically available in multidose vials, and dosages are calculated in units. The scale commonly used is U100, which is based on 100 units of insulin contained in 1 mL of solution. An insulin syringe is also calibrated in units. Insulin is also available in injection pens, which eliminate the need to prepare two medications in one syringe. Insulin injection pens are prefilled devices that combine the insulin container and syringe. Patients attach a needle for each administration, dial a dose of insulin, and depress a plunger to administer the dose. Use of an insulin injection pen is outlined in the Skill Variation in Skill 5-7 on page 244.

Assessment

Assess the appropriateness of the drug for the patient. Review the medical history and allergy, assessment, and laboratory data that may influence drug administration. Determine the compatibility of the two medications. Not all insulins can be mixed together. Assess the contents of each vial of insulin. It is very important to be familiar with the particular drug's properties to be able to assess the quality of the medication in the vial before withdrawal. Unmodified preparations of insulin typically appear as clear substances, so they should be without particles or foreign matter. Modified preparations of insulin are typically suspensions, so they do not appear as clear substances. Check the expiration date before administering the medication. Assess the patient's knowledge of the medication. If the patient has a knowledge deficit about the medication, this may be the appropriate time to begin education about the medication. Check the patient's blood glucose level, if appropriate, before administering the insulin. Verify patient name, dose, route, and time of administration.

Actual or Potential Health Problems and Needs

Many actual or potential health problems or issues may require the use of this skill as part of related interventions. An appropriate health problem or issue may include:

• Infection risk
• Knowledge deficiency
• Hyperglycemia

Outcome Identification and Planning

The expected outcomes to achieve when mixing two different types of medication in one syringe are the accurate withdrawal of each medication into a syringe in a sterile manner, the medication is free from contamination, and the proper dose is prepared.

Implementation

Action	Rationale
1. Gather equipment. Check each medication prescribed against the original in the health record, depending on facility policy and the medication order system in place. Clarify any inconsistencies. Check the patient's health record for allergies.	The prescription is the legal record of prescribed medication interventions. This comparison helps to identify errors that may have occurred when orders were transcribed. Computer provider order-entry (CPOE) systems allow prescribers to send electronic medication prescriptions directly to the pharmacy located in a health care facility and to outpatient pharmacies.
2. Know the actions, special nursing considerations, safe dose ranges, purpose of administration, and adverse effects of the medications to be administered. Confirm the compatibility of the medications in one syringe. Consider the appropriateness of the medication for this patient.	This knowledge aids the nurse in evaluating the therapeutic effect of the medication in relation to the patient's health status and can also be used to educate the patient about the medication.
3. Perform hand hygiene.	Hand hygiene prevents the spread of microorganisms.
4. Move the medication supply system to the outside of the patient's room or prepare for administration at the medication supply system in the medication area. Alternatively, access the medication administration supply system at or inside the patient's room.	Organization facilitates error-free administration and saves time.
5. Unlock the medication supply system or drawer. Enter the passcode and scan employee identification, if required.	Locking the supply system or drawer safeguards each patient's medication supply. Facility accrediting organizations require medication supply systems to be locked when not in use. Entering the passcode and scanning ID allows only authorized users into the system and identifies the user for documentation by the computer.
6. Prepare medications for one patient at a time.	This prevents errors in medication administration.
7. Read the eMAR/MAR and read the label when selecting the proper medications from the medication supply system or the patient's medication drawer.	This is the first check of the label.
8. Read the label and compare the labels with the eMAR/MAR. Check expiration dates and perform dosage calculations, if necessary. Scan the bar code on the package, if required.	This is the second check of the labels. Verify calculations with another nurse to ensure safety, if necessary.
9. If necessary, remove the cap that protects the self-sealing stopper on each vial.	The cap protects the self-sealing top.
10. If the medication is a suspension (e.g., a modified insulin, such as NPH insulin), roll and agitate the vial to mix it well.	There is controversy regarding how to mix insulin in suspension. Some sources advise rolling the vial; others advise shaking the vial. Consult facility policy or pharmacist. Regardless of the method used, it is essential that the suspension be mixed well to avoid administering an inconsistent dose.
11. Scrub the self-sealing stopper top with the antimicrobial swab and allow it to dry.	The antimicrobial swab removes surface microbial contamination. Allowing the antimicrobial solution to dry completely (5 to 20 seconds) ensures complete antimicrobial effectiveness (Gorski et al., 2021; Slater et al., 2018). Drying also prevents antimicrobial solution from entering the vial on the needle.
12. Remove the cap from the needle by pulling it straight off. Touch the plunger only at the knob. Draw back an amount of air into the syringe that is equal to the dose of modified insulin to be withdrawn.	Pulling the cap off in a straight manner prevents accidental needlestick. Handling the plunger only by the knob ensures sterility of the shaft of the plunger. Before fluid is removed, injection of an equal amount of air is required to prevent the formation of a partial vacuum, because a vial is a sealed container. If not enough air is injected, the negative pressure makes it difficult to withdraw the medication with repeated use.
13. Hold the modified vial on a flat surface. Pierce the self-sealing stopper in the center with the needle tip and inject the measured air into the space above the solution (Figure 1). Do not inject air into the solution. Withdraw the needle.	Unmodified insulin should never be contaminated with modified insulin. Placing air in the modified insulin first without allowing the needle to contact the insulin ensures that the second vial-entered (unmodified) insulin is not contaminated by the medication in the other vial. Air bubbled through the solution could result in withdrawal of an inaccurate amount of medication.
14. Draw back an amount of air into the syringe that is equal to the dose of unmodified insulin to be withdrawn.	A vial is a sealed container. Therefore, injection of an equal amount of air (before fluid is removed) is required to prevent the formation of a partial vacuum. If not enough air is injected, the negative pressure makes it difficult to withdraw the medication.
15. Hold the unmodified vial on a flat surface. Pierce the self-sealing stopper in the center with the needle tip and inject the measured air into the space above the solution (Figure 2). Do not inject air into the solution. Keep the needle in the vial.	Air bubbled through the solution could result in withdrawal of an inaccurate amount of medication.
16. Invert the vial of unmodified insulin. Hold the vial in one hand and use the other to withdraw the medication. Touch the plunger only at the knob. Draw up the prescribed amount of medication while holding the syringe at eye level and vertically (Figure 3). Turn the vial over and then remove the needle from the vial.	Holding the syringe at eye level facilitates accurate reading, and the vertical position allows easy removal of air bubbles from the syringe. First dose is prepared and is not contaminated by insulin that contains modifiers.
17. Check that there are no air bubbles in the syringe.	The presence of air in the syringe would result in an inaccurate dose of medication.
18. Check the amount of medication in the syringe with the medication dose and discard any surplus.	Careful measurement ensures that the correct dose is withdrawn.
19. Recheck the vial label with the eMAR/MAR.	This is the third check to ensure accuracy and to prevent errors. It must be checked now for the first medication in the syringe, as it is not possible to ensure accuracy once a second drug is in the syringe.
20. Calculate the endpoint on the syringe for the combined insulin amount by adding the number of units for each dose together.	This allows for accurate withdrawal of the second dose.
21. Insert the needle into the modified vial and invert it, taking care not to push the plunger and inject medication from the syringe into the vial. Invert the vial of modified insulin. Hold the vial in one hand and use the other to withdraw the medication. Touch the plunger only at the knob. Draw up the prescribed amount of medication while holding the syringe at eye level and vertically (Figure 4). Take care to withdraw only the prescribed amount. Turn the vial over and then remove the needle from the vial. Carefully recap the needle. Carefully replace the cap over the needle.	The previous addition of air eliminates the need to create positive pressure. Holding the syringe at eye level facilitates accurate reading. Capping the needle prevents contamination and protects the nurse against accidental needlesticks. A one-handed recap method may be used as long as care is taken to ensure that the needle remains sterile.
22. Check the amount of medication in the syringe with the medication dose.	Careful measurement ensures that correct dose is withdrawn.
23. Depending on facility policy, the third check of the label may occur at this point. If so, read the label and recheck the labels with the MAR before taking the medications to the patient. However, many facilities require the third check to occur at the bedside, after identifying the patient.	This third check ensures accuracy and helps to prevent errors. Note: Many facilities require the third check to occur at the bedside, after identifying the patient and before administration.
24. Label the vials with the date and time opened and beyond-use date, and store the vials containing the remaining medication, according to facility policy.	Because the vial is sealed, the medication inside remains sterile and can be used for future injections. Labeling the opened vials with a date and time limits its use after a specific time period. The CDC recommends that medications packaged as multiuse vials be assigned to a single patient whenever possible (CDC, 2019; Dolan et al., 2016).
25. Label the syringe with the medication's name, dose, and amount date (The Joint Commission, 2021).	Unlabeled syringes are unidentifiable and may lead to a medication administration error (The Joint Commission, 2021).
26. Log out of and/or lock the medication supply system before leaving it.	Locking the medication supply system or drawer safeguards the patient's medication supply. Facility accrediting organizations require medication supply systems to be locked when not in use.
27. Perform hand hygiene.	Hand hygiene deters the spread of microorganisms.
28. Proceed with administration, based on prescribed route.	See appropriate skill for prescribed route.

Evaluation

The expected outcomes have been met when the medication was withdrawn into the syringe in a sterile manner, it was free from contamination, and the proper dose was prepared.