Ampoules (Figure 15.21) are traditionally single‐dose glass containers although increasingly plastic ampoules are used for a number of products (Downie et al. [82]). They are sealed by heat fusion to exclude any contamination. They have a thin wall that allows rupture of the glass to expose the contents of the liquid or powder. There is a narrow constriction leading to the neck, which is often marked with a white ring, which indicates the place where the neck can be snapped off (Downie et al. [82]). Ampoule opening devices of various designs are available. Ampoules are available in several sizes, from 1 to 20 mL (Ostendorf [277]).

Vials (Figure 15.22) are glass containers with a rubber closure that can be penetrated to allow the addition of a diluent to dissolve powder contents and withdrawal of a dose via the needle. The exposed rubber surface is usually covered by a protective pull‐off metal or plastic cap, which prevents tampering or damage but does not provide sterility (Downie et al. [82], Ostendorf [277]). A vial may be packaged with a specific transfer needle, and it is important to follow the manufacturer's instructions in these instances. Most vials are intended for single use but a small number are multidose containers.

A number of drugs (e.g. insulin and low‐molecular‐weight heparins) are presented in pre‐filled syringes with a needle attached. There are various designs and the nurse must ensure that they are familiar with the device being used. Drugs should never be transferred from these specialist dosage forms into other containers or syringes for administration due to the danger of error (NHS England [232], NPSA [274]). In addition, there are a number of pre‐prepared syringes that contain 0.9% sodium chloride specifically for flushing or ready‐to‐administer medicines for use in emergency situations.

Syringes are commonly plastic and disposable, although occasionally a medicine must be administered via a glass syringe (e.g. adenosine). They consist of a graduated barrel and a plunger and a tip. It is the tip that classifies the type of syringe as either Luer‐Lok or Luer‐Slip (Figure 15.23).

Syringes come in various sizes, from 1 to 60 mL. The choice of syringe is made according to the volume of medication to be administered so it is important to choose the smallest syringe possible to ensure accuracy (Downie et al. [82], Ostendorf [277]). For Luer‐Lok syringes, the needle must be twisted onto the tip and ‘locked’ into position. This provides security and these syringes are recommended for use with intravenous medicines, especially cytotoxic medications and any medicines administered via a syringe pump. Luer‐Slip syringes tend to be used for intramuscular and subcutaneous injections. Insulin syringes are low‐dose syringes often calibrated in units and are only used for insulin administration (Downie et al. [82], NICE [253], Ostendorf [277]). They should be stored and distinguished from intravenous syringes (MHRA [205], Reid [297]). Injection pens are pre‐filled syringes that contain a disposable cartridge. They provide a convenient delivery method and allow patients to self‐administer their medications subcutaneously (e.g. insulin and adrenaline) (Ostendorf [277]).

Following intrathecal incidents, the NPSA ([273]) issued a safety alert stating that all spinal (intrathecal) bolus doses and lumbar puncture samples (part A) and all epidural, spinal (intrathecal) and regional anaesthesia infusions and bolus doses (part B) should be performed using syringes, needles and other devices with connectors that will not also connect with intravenous equipment.

A hypodermic needle is composed of three parts (Figure 15.24):

Needle sizes are known as ‘gauges’ – for example 19 G (used for intravenous injections), 21 G (used for intramuscular injections), 23 G (used for subcutaneous injections) and 25 G (used for intradermal injections). This indicates their diameter. The higher the gauge, the finer the needle, and selection is made depending on the viscosity of the liquid to be injected (Downie et al. [82], Ostendorf [277]). Needles vary in length from 10 to 16 mm, and selection of length will depend on the size and weight of the patient, and the type of tissue into which the drug is to be injected (e.g. longer for intramuscular injections and shorter for subcutaneous injections). Each needle is enclosed in a removable plastic guard and then sealed in a sterile pack. Filter needles may be used to prevent drawing up glass and rubber particles into the syringe (Downie et al. [82], Ostendorf [277]).

There are now a variety of safety needles available to prevent needle stick injury, where a plastic guard or sheath slips over the needle after an injection (EASHW [84]) (Figure 15.25) or the needle retracts into the barrel.

Three categories of needle bevel are available:

Following is how to calculate the drug volume required from the stock strength:

Another way of expressing this is to start with the strength you want, divide it by the strength of the stock you have, and then multiply the result by the volume of stock solution.

The volume of the injection in a single‐dose container is sufficient to permit the withdrawal and administration of the required dose using a normal technique.

Multidose aqueous injections contain a suitable antimicrobial preservative at an appropriate concentration except when the preparation itself has adequate antimicrobial properties. When it is necessary to present a preparation for parenteral use in a multidose container, the precautions to be taken for the preparation's administration and more particularly for its storage between successive withdrawals will be provided.

Parenteral infusions are sterile, aqueous solutions or emulsions with water; they are free from pyrogens and are usually made isotonic with blood. They are principally intended for administration in large volumes. Parenteral infusions do not contain any added antimicrobial preservative (British Pharmacopoeia 2018, Hillery et al. [128]).