ORAL ADMINISTRATION

Tablets, capsules and liquid preparations are relatively easy to administer and are suitable delivery systems for drugs that are effective when given orally. If a tablet or capsule sticks in the oesophagus, it can cause irritation to the point of ulceration of the mucosa, especially with drugs such as ferrous salts. Small tablets are generally easy to swallow. Larger uncoated tablets may present problems; torpedo-shaped coated tablets are more patient-friendly. It is important that soluble tablets and effervescent tablets are completely dissolved in water prior to administration. To ensure complete transit from mouth to stomach, tablets and capsules should be swallowed with a large drink, ideally when standing. Where this is not possible, the patient should be in the sitting position (Channer 1985).

The disguising of medicines in food and drink without informed consent is a complex issue. Covert administration of medicines to patients in Norwegian nursing homes was revealed in a study of 243 patients, of whom 95% had their drugs mixed in food and beverages routinely (Kirkevold and Engedal 2005).

The principles involved are underpinned by the Human Rights Act 1998. Registered nurses need to be sure that what they are doing is in the best interests of the patient, and are reminded of their accountability in any decision they make regarding what may be seen as misleading the patient (Nursing and Midwifery Council 2006, pp. 7-8). The doctor and pharmacist are available to suggest alternatives and to provide professional support. Any duty of care argument should be supported by good record keeping (Nursing and Midwifery Council 2006, p. 8).

SUBLINGUAL ADMINISTRATION

First-pass metabolism is avoided when drugs are given by the sublingual route (i.e. under the tongue), because the drug passes directly into the general blood circulation via the blood vessels on the undersurface of the tongue. Sublingual tablets are uncoated, ready for absorption. Once the tablet has been placed under the tongue, the patient should keep the mouth closed and refrain from swallowing saliva for as long as possible, as this contains the drug that will be absorbed. As absorption through the oral mucosa is rapid, the effects of the drug become apparent within a minute or two.

Tablets to be given by this route must be prescribed as such. The method of administration is simple, requiring no liquid and demanding little effort from the patient. The cooperation of the patient is necessary, however, and a clear explanation of this method of administration should be given. Although no harm will ensue if the tablet is swallowed, the patient will benefit from the drug only if it is taken sublingually.

The ease with which drugs can be given by this route can be used to advantage in pre- and postoperative patients and in those who are terminally ill, in whom swallowing of tablets can be a problem.

The sublingual route is also useful when there is risk of symptoms arising unexpectedly and when a rapid effect is wanted, such as in angina. Patients who are prescribed glyceryl trinitrate tablets for prevention of anginal attacks should be advised to carry with them a small supply of the tablets at all times. The expiry date (8 weeks after opening) should be carefully noted on the label of the container. Once individual patients realise which activities tend to precipitate an attack, they should get into the habit of placing the tablet under the tongue just before embarking on any of these activities. When the tablet is used to alleviate an anginal attack, it should be taken immediately the pain is experienced and retained under the tongue until the pain is relieved, after which any of the tablet remaining is spat out. This may help to prevent headache caused by cerebral vasodilatation, which often follows administration of this drug. Sublingual glyceryl trinitrate may also be administered in the form of an aerosol spray.

BUCCAL ADMINISTRATION

When a tablet is to be held in the mouth against the mucous membranes, the method of administration is described as buccal. This specific route appears on the packaging and on the prescription. It refers to the area high up between the upper lip and the gum where the dosage form is left to dissolve. Tablets for buccal administration are uncoated to facilitate absorption. Glyceryl trinitrate and prochlorperazine maleate are available as buccal tablets. The site chosen should be varied to reduce the risk of dental caries.

MEDICINE ROUNDS

Despite an increase in self-administration, the majority of medicines in hospital are still administered consecutively to groups of patients in the form of a medicine round (Box 4.2). A medicine trolley or an individual medicine cabinet may be used.

PRESENTATION AND PREPARATION OF SMALL-VOLUME INJECTIONS

Small-volume injections are presented in the form of an ampoule or a rubber-capped vial.

AMPOULES

Ampoules are mostly made of glass (an inert material) of special quality that does not react with the contents. Plastic ampoules are now used for certain products. Sizes range from 0.25–50 mL. Ampoules normally contain solutions ready for use but may contain a sterile powder for reconstitution.

An ampoule has a body containing the drug, a top, and a narrow constriction in between referred to as the neck (Fig. 4.1). The neck may be marked with a white ring, or the top may have a coloured spot. These indicate where the ampoule is to be snapped off to enable the contents to be accessed. Some ampoules have coloured rings on the neck that help in avoiding mix-ups. These rings must not be used to identify the product.

Fig. 4.1 Ampoule.

Ampoule-opening devices of various designs are available (Fig. 4.2). Plastic ampoules are accessed by twisting off a tab on the neck or by direct penetration with a needle at a site indicated on the ampoule. Ampoules whose tops have been removed cannot be resealed and are therefore for single use only. Any unwanted contents must be discarded.

Fig. 4.2 Example of an ampoule-opening device.

After shaking down any solution that has entered the neck, the neck is wiped with an alcohol swab to remove any surface contamination and the top snapped off using an ampoule sleeve to protect the fingers from glass spicules and/or any sharp edges. Less commonly, it may be necessary to make a scratch on the ampoule using a small file.

VIALS

Rubber-capped vials are used for solutions for injection and sterile powders for reconstitution (Fig. 4.3). They are squat glass containers closed with a rubber plug that is held in place by a metal ring. The exposed rubber surface is generally covered with a protective pull-off metal or plastic disc.

Fig. 4.3 Rubber-capped vial.

Rubber-capped vials are capable of being used as multidose containers, because the rubber plug is self-sealing if correctly used. They should, however, be used as such only if the stability of the contents permits and there is a suitable antimicrobial preservative present in the formulation.

The disc is removed and the exposed surface swabbed with an alcohol swab and allowed to dry, prior to puncturing the centre of the rubber plug with a needle. To facilitate withdrawal of fluid, the plunger of the syringe is first withdrawn and air injected, the volume of air being the same as the volume of fluid to be withdrawn. The required dose is removed or the required volume of the appropriate reconstitution fluid is added prior to the removal of the dose. Great care is essential in calculating what portion of the total volume is required from multidose vials. It is vitally important to follow the instructions regarding reconstitution and to ensure that the powder is dissolved before withdrawing the dose.

The needle is then changed after drawing up the injection and before injecting the patient, in case particles of rubber are retained inside the needle. Another good reason is that when a needle is inserted through the rubber cap, it may become dulled or the needle coating that helps it glide through the skin may be removed (Beyea and Nicoll 1996). Besides, because of the high risk of needlestick injury when resheathing a needle, the practice of using a new needle for administering the injection to the patient is obligatory (Royal College of Nursing 2006).

RECONSTITUTION OF MEDICINES FOR INJECTION

Where there are problems of stability, the drug may be presented in powder form, which requires reconstitution with a diluent. Reconstitution is most often done using water for injections, although in certain instances special diluents may be required. It should be recognised that the addition of 1 mL of diluent to 250 mg of a drug will produce a volume in excess of 1 mL. Normally this is of little consequence, but it may be important if a fraction of the total content of the vial is to be administered. For emaciated patients, the volume of reconstituting fluid should be the minimum compatible with the physical and other properties of the drug such as solubility, and any possible local irritancy should be taken into account. Once the contents of a multidose vial have been reconstituted, the vial must be dated and stored in the refrigerator.

On occasion, it may be desirable to combine two drugs in the same injection. This may present problems such as the physical/chemical incompatibility in the syringe and in the management of any subsequent drug reaction. The prime considerations here should be the safety and comfort of the patient. Comfort of the patient, however, should not be allowed to detract from safety in drug therapy. The advice of the prescriber and clinical pharmacist will often be helpful in resolving these difficult situations.

ROUTES OF ADMINISTRATION

The routes most commonly used for administering injections are:

Intravenous medicines given by direct venepuncture are administered only by a doctor. A nurse who has undertaken specific training and is in possession of authorisation to do so may administer intravenous medication when venous access has already been established (Clinical Resource and Audit Group of NHS Scotland 2002). In clinical practice, there is widespread use of the intravenous route for the administration of drugs such as antibiotics and diuretics. However, some drugs still require to be given by either the subcutaneous or intramuscular route, and therefore nurses must maintain the skills involved.

The subcutaneous route is generally used for ad-ministering small doses of non-irritating, water-soluble substances. Drugs commonly given subcutaneously include:

Patients receiving outpatient treatment for certain ongoing conditions are encouraged to self-administer subcutaneous medication when possible. Examples include the administration of insulin, heparin, interferon and granulocyte-colony stimulating factor. Alternatively, a family member may be taught to do this.

The intramuscular route is used for administering formulations such as aqueous solutions, oily solutions and aqueous suspensions. Drugs commonly given intramuscularly include:

RATE OF ABSORPTION

The rates at which drugs are absorbed and take effect after subcutaneous or intramuscular injection depend on two factors. These are the local blood circulation and the nature of the drug solution or suspension. Subcutaneous absorption occurs chiefly through the capillaries and is much faster compared with absorption following oral medication but usually slower than intramuscular absorption because of muscle tissue’s excellent blood supply.

Absorption following intramuscular injection may be speeded up by massaging the area of injection. However, insulin-dependent diabetics are discouraged from massaging the site vigorously, in an attempt to preserve the state of the capillaries. An inflamed or oedematous site should be avoided when administering subcutaneous or intramuscular injections, so as to prevent a worsening of the inflammation/oedema and consequently a delay in absorption. In states of shock, blood flow to the skin and superficial muscle may be greatly reduced, thus reducing the absorption of drugs from these sites. In this case, intravenous injection should be used.

SYRINGES

A syringe consists of a barrel and a plunger (Fig. 4.4). The barrel is graduated. The plunger has a rubber stopper attached. Syringes are available in various sizes (e.g. 1, 2, 5, 10 and 20 mL). The choice of syringe is made according to the volume of medication to be injected. It should be noted, however, that insulin must always be measured using an insulin syringe. The tip of a syringe can vary, with the concentric Luer tip being the one used for subcutaneous and intramuscular injections. It is also used for introducing medication via an already sited intravenous cannula. For direct intravenous injections, the eccentric Luer tip is used to allow the needle to lie within the vein wall without puncturing the distal wall. The Luer tips of syringes interlock to an international standard with needle hubs.

Fig. 4.4 Syringe.

Disposable syringes are made of a plastic material that is compatible with most substances to be injected. There are one or two exceptions, however. Paraldehyde, for example, should be administered using a glass syringe, because it dissolves plastic and rubber on prolonged contact. Syringes are individually sealed in a sterile pack. Before use, a check should be made that the seal has not been broken. Once a syringe has been removed from its pack, the utmost care is required to prevent contamination of the tip of the syringe.

NEEDLES

A needle consists of a hub and a cannula (Fig. 4.5). The cannula is hollow and is made of strong flexible steel that has been siliconised to assist penetration. For the same reason, the tip of the cannula is bevelled. Different types of needle have a different bevel. A shorter bevel encourages minimal penetration, as is required in an intradermal injection (see p. 63). A longer bevel allows easier deep penetration, as needed for an intramuscular injection (see p. 56). The gauge of the cannula is an indication of its diameter. The higher the gauge, the finer the bore. Higher gauges are used for ‘watery’ solutions and make for less painful injections. Low gauges are essential for injecting viscous (syrupy) solutions.

Fig. 4.5 Needle.

Needle lengths also vary. Selection of length depends on the route of the injection as well as the patient’s age and physical build. A study by Chan showed that only 32% of patients received the correct dose of intramuscular injection, the reason being that needles could not penetrate the muscle due to excessive fat in patients’ buttocks caused by obesity (Anonymous 2005).

Each needle is enclosed in a removable guard and individually sealed in a sterile pack. Before use, a check should be made to ensure that the pack has not been damaged. Once a guard is removed, the needle should be in one of three places only: in the ampoule or vial containing the medication, in the patient or in the sharps container.

For drawing up any injection from a glass ampoule, it is important to use a needle with a bore that is 21-gauge or smaller to filter out any shards of glass that may have entered the ampoule (Shaw and Lyall 1985).

For administering subcutaneous injections, a short fine-bore needle is used. For adults, this may be ½ inch (13 mm) or ⅝ inch (16 mm), 25-gauge or 26-gauge; ½ inch (13 mm), 26-gauge; or ⅜ inch (10 mm), 27 gauge.

For administering intramuscular injections, the needle used has to be sufficiently long to reach deep into the muscle so as to increase the speed of effect and to reduce the likelihood of the drug seeping back along the needle track. For adults, a 1½-inch (40 mm), 21-gauge (0.8 mm) needle is normally used. In severely emaciated adults, a 1-inch (25 mm), 23-gauge (0.6 mm) needle may be used.

When drawing up and injecting drugs with a known potential to cause sensitivity reactions, disposable gloves should be worn to prevent possible contact with the skin and the development of a sensitivity reaction. The special precautions that require to be taken when handling cytotoxic drugs are given in Chapter 19.

VOLUME

When preparing an injection, the nurse should give consideration to the volume that may be effectively accommodated in one site. Apart from the route to be used, the patient’s age and physical build are factors that will influence the decision. Normally, the following would apply.

SITE

The sites most commonly used for subcutaneous injections (Fig. 4.6) are as follows:

Fig. 4.6 Sites for administering subcutaneous injections.

(The back and lower loin may also be used.)

The sites most commonly used for intramuscular injections are as follows:

(The deltoid is used for hepatitis B and influenza vaccines.)

It is vital that the intramuscular injection is confined to the upper outer quadrant of the buttock or the anterolateral aspect of the mid-thigh so as to avoid damage to the sciatic nerve (Fig. 4.7) and to avoid penetrating a major blood vessel.

Fig. 4.7 Upper outer quadrant of the buttock (shaded area).

Rotation of the sites used for subcutaneous and intramuscular injections helps to reduce the likelihood of irritation and improves absorption. Rotation within the sites is also important. Patients who, for example, have to repeatedly self-administer subcutaneous injections may be taught to visualise a clock face on the site and systematically work round it. Where nurses are repeatedly administering injections, the site used on each occasion may be plotted on a diagram held at the bedside. Before administering any type of injection, the skin should be inspected on each occasion. Lesions, such as birthmarks, moles or scars, and inflamed or oedematous sites should be avoided.

SKIN PREPARATION

Despite now quite old research findings, old habits die hard. It is not considered necessary to use an alcohol swab to disinfect the skin prior to the administration of injections. Although there are inconsistencies in practice, the lack of skin preparation does not result in infections (Dann 1969, Koivisto and Felig 1978, Workman 1999). Torrance (1989) cites two studies that prove this point. One describes a series of 1078 injections given by all routes without any skin preparation, which resulted in no case of systemic or local infection. The second was a study of 7000 insulin injections given to a group of diabetic patients without skin cleansing, with no infection noted. Lipids in the epidermis provide an antibacterial barrier, so that removal of the lipids may encourage bacterial colonisation (Torrance 1989).

Clinical evidence suggests that no harm will be caused by pricking the skin so long as it is socially clean. Contaminated skin will need preparation to produce a low bacterial count. In this case, the site should first be made socially clean followed by a 30-s rub using an ‘alcohol swab’ (alcohol swabs contain 70% alcohol and a disinfectant such as chlorhexidine). The skin should then be allowed to dry for a further 30 s before proceeding to ensure that bacteria are rendered inactive (Cullen 2004) and so that the antiseptic does not cause irritation by being injected into the tissues. In immunosuppressed patients, the skin must be cleansed in this way, as this group of patients may become infected by inoculation of a relatively small number of pathogens.

ANGLE

The angles at which the needle is directed for subcutaneous and intramuscular injections are illustrated in Figure 4.8. It is common practice for subcutaneous injections of, for example, heparin or insulin to be given into the abdomen at an angle of 90° using a very short subcutaneous needle. An angle of between 45 and 90° may be used with a longer subcutaneous needle. Where the syringe and needle have been previously prepared in a pack (as for self-administration), the needle is usually very short and an angle of 90° is recommended.

Fig. 4.8 Angles for the administration of (A) subcutaneous and (B) intramuscular injections.

IRRITANT OR STAINING SUBSTANCES

The injection may be known to irritate the tissues and stain the skin if it is allowed to seep along the needle track to the epidermis (e.g. iron sorbitol injection). To prevent this, several precautions should be taken. After the syringe is filled, the needle is changed so that the substance is contained in the syringe only and is less likely to drip from the tip of the needle as it penetrates the skin. To reduce pain as well as the risk of staining, the injection is made deep into the muscle of the upper outer quadrant of the buttock. The arm and thigh do not allow for the depth required and so should not be used.

A 21-gauge needle is normally suitable, but it is important that it is long enough to reach the muscle. As a rule of thumb, a 1½-inch (40 mm) needle will do for most normal-sized adults. Obese patients (e.g. > 90 kg) will require a 2-inch needle. The so-called Z-track technique must be used. This technique involves displacement of the skin and subcutaneous tissue laterally prior to injection (Fig. 4.9). The injection is made slowly and steadily. Before withdrawing the needle, 10 s should be allowed to elapse so that the muscle mass can accommodate the volume of the injection. The site is not massaged, otherwise the medication may be forced into the subcutaneous tissue, causing irritation.

Fig. 4.9 Z-track technique: (A) Injection (B) Post-injection.

REDUCTION OF PAIN

For most people, the prospect of receiving an injection of any kind is not one that they relish. Pain caused by injections can be reduced in a number of different ways (Box 4.3). First, it is important to try to encourage patients to relax. This may be achieved by explaining to them what they should do. Patients should be positioned so that they are at ease. For example, for subcutaneous injections into the upper arm, the patient should be sitting with the hand resting on the iliac crest; for intramuscular injections, the patient should be lying on, as opposed to leaning over, a couch or bed.

When the buttock is the chosen site for intramuscular injection, administration may be made less painful by asking the patient to adopt the prone position and to point the feet inwards. Internal rotation of the femur helps to relax the gluteus maximus muscle. Alternatively, the patient may lie on one side with the lower leg extended and the upper leg flexed.

As a general rule, with intramuscular injections the needle should be inserted (and withdrawn) quickly. Subcutaneous injections require the needle to be steadily pushed through the skin into the tissues and then eased out gently on completion of the injection.

Fine-bore needles create less pain on puncturing the skin and necessitate slow injection of the fluid. Pain can result from injecting too large a volume of fluid at one site or injecting the drug too quickly, resulting in improper distribution of the drug. The medication should be injected using slow, steady pressure at a rate of about 10 s/mL (Beyea and Nicoll 1996).

The skin may be cooled using a volatile spray such as ethyl chloride. A further possibility is to use a local anaesthetic agent such as Emla (eutectic mixture of local anaesthetic) cream.

Subcutaneous administration may be carried out by means of a high-pressure jet of liquid, using an injector that delivers an accurate dose without the aid of a needle. This technique may be useful in mass inoculation programmes. There is a reduction in pain to the patient and no risk of needlestick injury. The risk of transmitting blood-borne infections by this method should be carefully considered.

Use of the Z-track technique (see p. 57) may also reduce the discomfort associated with intramuscular injections, because there is less likelihood of the medication leaking into the subcutaneous tissue by this method.

Needle phobia is a very real problem to those who suffer from it. Ten per cent of the population is said to be affected by it. Little is written about it. There have been instances of vasovagal reflex reaction (fainting) even resulting in death. Patients may need courage to admit they suffer from needle phobia, just as they need courage to admit they suffer from a painful condition. Physicians must learn how fearful the problem is to the individual concerned and that many appointments and opportunities are missed because of it, with consequent increase in morbidity. The development of microneedles that are 0.15–0.3 mm long will allow permeability of the skin without reaching pain receptors.

ADMINISTRATION

The process of checking a medicine for injection against the prescription is the same as for the administration of any medicine. This should be done immediately prior to the administration procedure. It is not acceptable to prepare a substance for injection in advance of its immediate use or to administer a medication drawn into a syringe by another nurse without him or her being present (Nursing and Midwifery Council 2006, p. 5). Hands must be washed thoroughly using chlorhexidine gluconate solution at the start and finish of the procedure. Asepsis must be maintained throughout, because puncturing the integument provides easy access for pathogenic micro-organisms. Every effort must be made to encourage the patient to relax and to minimise pain as far as possible. Extra support will be required for patients suffering from needle phobia. Careful disposal of syringes and needles is of great importance.

The procedure for administering a subcutaneous injection is outlined in Box 4.4. Patients may be taught to self-administer medication by this route. The procedure for administering an intramuscular injection is outlined in Box 4.5.

Box 4.4 Administration of subcutaneous injection

Documentation

• As for intramuscular injection

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