Injection sites & Equipment

Vials

Parenteral medications come packaged in vials, ampules, and premeasured syringes and cartridges. Vials are the most common packaging for medication that is administered parenterally. A vial is a plastic or glass container that has a rubber stopper (diaphragm) on the top. The rubber stopper is covered with a metal lid or plastic cover to maintain sterility until the vial is used for the first time. Some manufacturers do not guarantee a sterile top even though it is covered, and therefore it is necessary to wipe the top with alcohol pad with first use and any use after. Vials are available in different sizes. Multidose vials contain more than one dosage of the medication. The label on the vial will specify the amount of medication in a certain amount of solution, for example, 60 mg per mL or 0.2 mg per 0.5 mL. Multidose vials usually expire after 28 days unless the manufacturer states otherwise. Make sure you write the expiration date on the vial upon opening. Single-dose vials contain a single dosage of medication for injection. Many vials are single dose because it is safer. Even if medication is in a single-dosage vial, it should still be measured and drawn up according to the prescribed amount. The medication in a vial may be in liquid (solution) form, or it may contain a powder that must be reconstituted before administration. Reconstitution requires the adding a liquid diluent to a dry ingredient to make a specific concentration of a medication. ​​​​​​​

Withdrawal from a Vial Technique

Before withdrawing medication from a vial, wipe the top with alcohol and allow it to dry. A vial is a closed system, and air must be injected into it to allow for withdrawal of the medication. If air is not injected into the vial before the medication is withdrawn, a vacuum remains in the vial that makes the withdrawal of medication difficult. Inject air equal to the amount of solution being withdrawn into the air space between the solution and the rubber stopper, invert the vial, and the withdraw the desired volume of medication.

Ampule

An ampule is a sealed glass container designed to hold a single dose of medication. Ampules have a particular shape with a constricted neck. They are designed to snap open. The neck of the ampule may be scored or have a darkened line or ring around it to indicate where it should be broken to withdraw medication. ​​​​​​​

Withdrawal from an Ampule Technique

When withdrawing medication from an ampule, snap the neck off by grasping it with an alcohol wipe, sterile gauze, or ampule protector. Aspiration of the medication into a syringe occurs easily and may be accomplished with a filter needle, if required by the medical practice’s policy. A filter needle prevents withdrawal of glass or rubber particulate. When the needle is inserted into an ampule, take care to prevent the shaft and tip of the needle from touching the rim of the ampule. Withdraw medication into the syringe by gently pulling back on the plunger, which creates a negative pressure and allows the medication to be pulled into the syringe. Discard the needle used to withdraw the medication and replace it with a new needle.

Syringes

Premeasured Syringes

Premeasured syringes and cartridges are prefilled syringes that are single dosed and packaged with the needle that is provided by the manufacturer. These syringes are disposable and supplied already loaded with the substance to be injected. Premeasured syringes are convenient and help ease the administration process. They allow for convenience and efficiency, accuracy in dosing, reduced risk of infection and contamination, and reduced waste. You do not have to worry about the transfer of a medication from a vial to a syringe or about leaving a small percentage of the dose behind. Common prefilled syringes are often used for immunizations and for emergency administration, such as naloxone for overdoses and sodium bicarbonate for shock and cardiac arrests.

Hypodermic Syringe

There are generally three types of syringes: hypodermic, tuberculin, and insulin. Hypodermic syringes come in a variety of sizes from 0.5 to 60 mL and even larger. Syringes are calibrated or marked in milliliters but hold varying capacities. Of the small-capacity syringes, the 3 mL syringe is used most often for the administration of medication. Although many syringes are labeled in milliliters, a few syringes are still labeled with cubic centimeters (cc). Milliliter (mL) is the correct unit. The milliliter is a measure of volume, the cubic centimeter is a three-dimensional measure of space and represents the space that a milliliter occupies. The terms, although sometimes used interchangeably, are not the same. Many institutions are now purchasing syringes that indicate mL as opposed to cc, but either is acceptable for use.

Tuberculin Syringe

A tuberculin syringe is a narrow syringe that has a capacity of 0.5 mL or 1 mL. The 1-mL size is used most often. The volume of a tuberculin syringe can be measured on the milliliter scale. On the milliliter side of the syringe, the syringe is calibrated in hundredths (0.01 mL) and tenths (0.1 mL) of a milliliter. Tuberculin syringes are used to accurately measure medications given in very small volumes (e.g., heparin). This syringe is also often used in pediatrics and for diagnostic purposes (e.g., skin testing for tuberculosis). It is recommended that dosages less than 0.5 mL be measured with a tuberculin syringe to make certain that the correct dosage is administered to a patient. Dosages such as 0.42 mL and 0.37 mL can be measured accurately with a tuberculin syringe. When using a tuberculin syringe, read the markings carefully to avoid error.​​​​​​​

Insulin Syringe

Insulin syringes are designed for the administration of insulin only. Insulin dosages are measured in units. Insulin syringes are calibrated to match the dosage strength of the insulin being used. They are marked U-100 and are designed to be used with insulin that is marked U-100. U-100 insulin should be measured only in a U-100 insulin syringe. It is important to note that for U-100 insulin, 100 units = 1 mL. Insulin syringes do not have detachable needles. The needle, hub, and barrel are inseparable.