Safe administration of parenteral medications: Routine injections in general practice. Part 1

Administering medications by injection is just one of the many practical skills a practice nurse needs to master. Our two-part series offers practical advice on the drugs and techniques practice nurses need to be familiar with

A wide variety of different medications are administered by injection and the practice nurse should be both knowledgeable of the medication being administered and skilled in the administration techniques to ensure the process is safe, effective and as untraumatic as possible for the patient.

As with the administration of any medicine regardless of the route it is delivered, all registered nurses should work within the NMC Code¹ and follow the NMC standards for medicines management,² which state ‘as a professional, you are personally accountable for actions and omissions in your practice, and must always be able to justify your decisions,’1 and ‘you must know the therapeutic uses of the medicine to be administered, its normal dosage, side effects, precautions and contra-indications.’²

This article is the first of two, which will cover some of the more common parenterally administered medications that are given to treat, modify or stabilise a condition, provide replacement of lacking elements or are given to prevent conditions. While immunisations and vaccinations, such as the influenza vaccination, fall into this final category they are administered as a specific campaign whereas this article will focus on those injections that are given on an ongoing basis throughout the year. And while many of the medications have a UK license for different indications, only conditions that are treated in primary care will be discussed.

Injections covered within this article are:

• Hydroxocobalamin – Vitamin B12
• Methotrexate
• Sodium aurothiomalate
• Low Molecular Weight Heparin (LMWH)

Hormonal injections and injections used in mental health will be discussed in Part Two.

VITAMIN B12 – HYDROXOCOBALAMIN

Vitamin B12 injections are used to treat both pernicious anaemia and vitamin B12 deficiency.

Pernicious anaemia & Vitamin B12 deficiency

Vitamin B12 is a water-soluble vitamin required for metabolism, normal functioning of the brain and nervous system, and in the formation of blood cells. It is absorbed in the small intestine and for this to happen intrinsic factor produced in the parietal cells of the stomach must be present.

Pernicious anaemia is an autoimmune condition, which results in antibodies being produced that attack and damage the parietal cells causing cessation of intrinsic factor production. But any condition affecting the integrity of the parietal cells such as large ulcers or cancer will also affect the production of intrinsic factor, while disease damage such as Crohns disease or surgery to the small intestine such as ileal resection can result in malabsorption and a resulting vitamin B12 deficiency.³

Dietary vitamin B12 is found in meat, fish, eggs and milk, so vegetarian or vegan diets may result in deficiency as can certain drugs such as metformin and anticonvulsants.

Diagnosis of vitamin B12 deficiency or pernicious anaemia is made through history taking, looking for signs and symptoms (see Box 1) and blood tests – an initial full blood count may show a low or normal haemoglobin and macrocytosis (large cells). Subsequent investigations may reveal a vitamin B12 deficiency and the presence or absence of intrinsic factor antibodies.

Treatment for dietary vitamin B12 deficiency may be via dietary supplementation with vitamin B12 rich foods and/or oral tablets. However, the British National Formulary4 suggests there is little place for use of low dose oral vitamin B12 supplements, therefore in pernicious anaemia and non-dietary causes, the treatment is with parenteral replacement.

In the UK there are two licensed injectable preparations of Vitamin B12 – hydroxocobalamin and cyanocobalamin. Hydroxocobalamin is the recommended drug of choice as it remains in the body for three months versus one month with cyanocobalamin. Initial hydroxocobalamin treatment is usually a 1mg dose administered every other day for two weeks, followed by a three monthly maintenance dose of 1 mg – usually for life. Cyanocobalamin follows a similar regime.

Vitamin B12 should only be given once a diagnosis has been fully established and the patient advised of the potential side effects, which may include nausea, headaches, dizziness and fever.⁴

Administration is by intramuscular injection (see Figure 1 & Table 1).

Intramuscular injections

To give an intramuscular injection the skin should be stretched flat with one hand and the needle inserted at 90º to the skin (this is also known as the Z-Track method) deep into the muscle tissue. There is no need to aspirate and only gentle pressure should be applied after administration if bleeding occurs. Care should be taken to ensure the correct needle size is used to ensure delivery into the muscle and to prevent local reactions.⁵

METHOTREXATE

Methotrexate is an antimetabolite antineoplastic agent that inhibits folate metabolism thus interfering with DNA synthesis. It is therefore a valuable drug in diseases where treatment is based on reducing new cell production. Methotrexate also has both anti-inflammatory and immunosuppressive properties.⁶

It may be used:

• As a disease modifying anti rheumatic drug (DMARD) in the treatment of rheumatoid arthritis. Rheumatoid arthritis is an inflammatory condition which affects multiple synovial joints. It is usually the smaller joints such as the hands and feet that are affected and it differs from osteoarthritis in that it usually affects both sides symmetrically. Treatment consists of analgesia and medications used to slow or stop the progression of the disease and protect the bone structure. Methotrexate may be given orally but at times is administered parenterally as a deep intramuscular injection.⁷ Wegrzyn et al⁸ demonstrated increased efficacy with less side effects using the IM route.
• For dermatological conditions such as psoriasis (overproduction of skin cells resulting in a build up of immature flaky skin cells), pemphigoid (autoimmune disease resulting in skin splitting and blistering), sarcoidosis (inflammatory disease resulting in granuloma formation) and psoriatic arthritis (a type of inflammatory arthritis).
• Neoplastic diseases where it is used as a form of chemotherapy to decrease the production of cancer cells.
• For inflammatory bowel conditions to reduce or stop inflammation of the bowel.

Methotrexate is given by a once weekly deep intramuscular injection (Figure 1, Table 1). However, the doses differ dramatically depending on the condition being treated so it is essential the practice nurse administering the dose is aware of the indication to be able to check the correct dose is being given.

Methotrexate can be highly toxic therefore it is essential that patients are aware of the signs of potential adverse effects (see box 2) and understand the need for regular blood tests to monitor full blood count, renal and liver function - this is usually undertaken before treatment, then repeated initially every 1-2 weeks until stabilised then monitored every 2-3 months.⁴

The BNF should be consulted to check for any drug interactions with concurrent medications and patients advised that they should not self administer over the counter non steroidal anti-inflammatory drugs (NSAIDs) or aspirin, and should avoid alcohol during treatment.

Methotrexate is a human teratogen so is absolutely contraindicated in pregnancy. Because it causes genetic damage and has potential for chromosome irregularities, both male and female patients should avoid conception until 6 months after treatment has finished. Methotrexate is excreted in breast milk, so should be avoided in lactating females, and if treatment is essential, breast feeding should be stopped.

As methotrexate is a cytotoxic drug staff who are to administer it should undergo specific cytotoxic training before administering to ensure they are aware of correct procedures involved with handling, administration and disposal of the used syringe. Pregnant staff should not administer methotrexate.

SODIUM AUROTHIOMALATE

Sodium aurothiomalate, which contains gold, is also a DMARD used in the treatment of rheumatoid arthritis. Although the precise mechanism of action is unknown it is used to reduce joint inflammation, to slow disease progression and help to reduce further joint damage. However, sodium aurothiomalate is potentially toxic with up to 5% of patients experiencing adverse effects, therefore the patient should be monitored closely during treatment. The urine should be checked before each injection is given to look for proteinuria, which may indicate renal damage, together with a full blood count looking for signs of bone marrow suppression causing neutropenia, thrombocytopenia and anaemia.

These potential adverse effects mean it is contraindicated in severe renal and hepatic disease; certain blood disorders; pregnancy and lactation; systemic lupus erythematosus (SLE); and some dermatological conditions. It is essential to check that women of child bearing age are using a reliable method of contraception as it may be teratogenic.

The practice nurse should be aware that anaphylactoid reactions have been reported with sodium aurothiomalate., and should be able to recognise and treat it quickly. Anaphylactoid reactions are due to direct mast cell degranulation whereas anaphylactic reactions are mediated by immunoglobulin E (IgE). However, they both produce similar symptoms and are treated in the same way.

While gold may be given orally it is far less effective so is given by a deep intramuscular injection (Figure 1, Table 1), and is one of the few drugs that once given should be followed by gentle massage to the injection site.⁴ Again doses may differ for each individual patient and the patient should be made aware that it may take several doses before any benefit may be felt. The BNF4 suggests that if there is no improvement in the patient’s condition, the drug should be stopped. Therefore it is important for the practice nurse to monitor response and report back to the prescriber to prevent long-term use of an ineffective drug. However, for those patients where it is working and keeping the disease in remission, injections may be prescribed two-, three-, four- or six-weekly and continued for up to five years.

LOW MOLECULAR WEIGHT HEPARIN (LMWH)

LMWH is commonly administered for both the treatment and prevention of venous thromboembolic (VTE) conditions such as pulmonary embolism (PE) and deep vein thrombosis (DVT) (NICE 2012).⁹ LMWH is an anticoagulant that works by enhancing the effects of antithrombin. Antithrombin inhibits factors in the coagulation cascade, including factor IIa (thrombin) and factor Xa.

LMWH is used in preference to unfractionated heparin as it has equal efficacy with less risk of heparin induced thrombocytopenia (low levels of platelets) and there is no need to monitor activated partial thromboplastin time (APTT).

As the duration of action is longer than unfractionated heparin a once daily dosing regime can be used and the patient treated at home rather than in hospital. Often the patient is taught to self-administer the injections, but at times it may be necessary for the practice nurse to undertake this role. Oral heparin is poorly absorbed so needs to be given as an injection.

The dose given is dependent on both the patient’s weight and the condition being treated, and it is given by deep subcutaneous injection into the abdomen. LMWH is in a pre-filled syringe so care should be taken to calculate the amount necessary for the correct dose to be given to the individual patient. Unlike the usual technique for giving a subcutaneous injection (Figure 1, Table 1), the injection is given at 90º to the skin rather than 45º, although it is still necessary to bunch the skin before administration, and the sites of administration should be altered. The area should not be rubbed after the injection is administered, as this may increase the risk of bruising, and the injection should not be administered into a previous bruise.

As with any anticoagulation treatment there is a risk of bleeding so the patient should be advised to seek medical help if there is excessive bleeding of any kind.

Subcutaneous injections

The deep SC injection technique is usually reserved for patients with bleeding disorders. For a SC injection the skin should be bunched up and the needle inserted at a 45º angle to the skin, again there is no need to aspirate and gentle pressure should be administered if required (Figure 1, Table 1).

CONCLUSION

Healthcare provision develops and changes constantly so it is important to ensure the most up to date, evidence based information regarding medications and their administration are used to guide practice.

Patients should be central to any management plan to ensure individuality in the care provided. Where possible they should be encouraged to engage in a partnership approach to that care and be advised to report adverse effects and attend for monitoring as required.

The practice nurse however who administers the medicine must take full responsibility and accountability for their actions so adopting a systematic approach that includes the safe practice points above will ensure consistent high standards of quality care when administering parental medications.

REFERENCES

1.Nursing & Midwifery Council (2008) The code: Standards of conduct, performance and ethics for nurses and midwives. Nursing & Midwifery Council. London

2.Nursing and Midwifery Council (2010) Standards for medicines management. NMC. London.

3.Hoffbrand AV, Provan D. (2007) Macrocytic anaemias. In: Provan, D. (Ed.) ABC of clinical haematology. London: BMJ Publishing.

4.Joint Formulary Committee (2013) British National Formulary 65. London. BMJ Publishing and the Royal pharmaceutical Society.

5.Diggle L. Injection technique for immunisation. Practice Nurse 2007; 33 (1)

6.Electronic Medicines Compendium (2013) Methotrexate. Available at: http://www.medicines.org.uk

7.NICE (2009) Rheumatoid Arthritis: The management of Rheumatoid Arthritis in Adults. NICE clinical guideline 79. Available at : guidance.nice.org.uk cg79

8.Wegryzn J, Adeleine P, Miossec P (2004) Better efficacy of methotrexate given by intramuscular injection than orally in patients with rheumatoid arthritis. Annuls of the Rheumatic Diseases 2004;63(10):1232-1234

9.NICE (2012) Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing. NICE clinical guideline 144. Available at: guidance.nice.org.uk/cg144