INTRODUCTION

An adverse drug reaction (ADR) has been defined by the World Health Organization as ‘any response to a drug which is noxious, unintended and occurs at doses used for prophylaxis, diagnosis and therapy’. All pharmaceutical preparations are potentially harmful, and this is a key reason why many medicines are strictly controlled and available only on prescription. The safe use of medicines is an important issue for nurses, pharmacists, doctors, regulatory authorities, the pharmaceutical industry and the public. Health professionals have a responsibility to their patients, who themselves are increasingly aware of problems associated with drug therapy. It is essential that the practising nurse has a knowledge of the adverse effects of drugs and how to recognise and prevent them. The special roles performed by nurses give them a unique opportunity to help reduce the incidence of ADRs and to minimise their impact on patients.

A tragic event occurred in the early 1960s that involved a hypnotic called thalidomide. This drug proved to be teratogenic, and many babies with congenital limb defects were born to mothers who had taken this preparation in early pregnancy. This major disaster led to the establishment of regulatory agencies that enforce rigorous testing and evaluation of drugs prior to the granting of a product licence and subsequent marketing. In addition to these processes, detection and recording of ADRs that occur when the drug is in use are of vital importance. A well-established reporting system enables ADRs to be reported to the Committee on Safety of Medicines. Both prescribed and non-prescribed medicines are included in this system. Yellow reporting forms for ADRs are included in the British National Formulary (BNF).

DRUG-INDUCED GASTROINTESTINAL DISORDERS

Adverse drug reactions frequently affect the gastro-intestinal tract. This is understandable when one considers that this is the most common route for medication administration and the vast range of oral medicines now available. Nausea and vomiting are one of the commonest adverse effects experienced by patients. However, in many cases symptoms soon resolve with continued use. When this is not the case, a lower dose or an alternative preparation may need to be considered, otherwise a concurrent antiemetic may be required. If nausea and vomiting are severe, treatment may have to be stopped.

Non-steroidal anti-inflammatory drugs including aspirin are very widely used but have a potential to damage the gastrointestinal tract. NSAIDs are administered to reduce pain and inflammation, particularly in arthritis. This is achieved by inhibition of synthesis of certain prostaglandins. However, they also inhibit prostaglandins, which are protective to tissues, resulting in irritant effects on the gastric epithelium.

Adverse drug reactions including abdominal pain, nausea, diarrhoea and dyspepsia are experienced. NSAID-induced erosions can result in bleeding and perforation of the stomach and duodenum. The following guidance can help minimise the risk from NSAIDs.

Table 10.1 provides details of several of the more commonly experienced gastrointestinal adverse effects (dry mouth, taste disturbance, oesophageal reflux, nausea and vomiting, diarrhoea and constipation) and examples of drugs causing these.

Table 10.1 Examples of drugs causing gastrointestinal adverse drug reactions

DRUG-INDUCED MENTAL HEALTH DISORDERS

Drug-induced mental health disorders are relatively common. Most adverse psychiatric effects of drugs are classified as type A reactions, as they are dose-related or predictable, although a few are idiosyncratic type B reactions. Psychiatric symptoms are also a common feature of withdrawal reactions, which can occur after certain drug therapy is stopped, particularly when it is stopped abruptly. For example, rapid withdrawal of benzodiazepines may cause rebound insomnia and anxiety.

The risk of an individual experiencing a psychiatric reaction to a drug is greater if mental illness is present or has been experienced in the past. Other associated factors include alcohol or drug abuse. Drugs implicated in psychiatric reactions can cause more than one effect. For example, phenytoin can cause delirium, hallucinations and psychosis.

DRUG-INDUCED SKIN DISORDERS

Drug-induced skin eruptions are likely to be the most frequent adverse reaction seen by a nurse, because approximately 30% of reported drug reactions involve the skin. Reactions are frequently seen after immunisations and can range from mild to more severe (Fig. 10.1).

Fig. 10.1 Adverse effect following immunisation.

DRUG-INDUCED BLOOD DISORDERS

Like other ADRs, those affecting the blood can be divided into type A and type B reactions. Type A reactions can be predicted from the therapeutic action of the drug. Bone marrow suppression by cytotoxic drugs is a common type A effect.

The nurse has a role in advising patients prescribed high-risk drugs to seek urgent medical attention should they develop signs or symptoms suggestive of haematological ADRs. Patients will often present with a sore throat, mouth ulcers, rash, malaise, fever, bruising or bleeding. For some high-risk drugs, the risk is such that regular monitoring of the blood count is advised. These include amphotericin, clozapine, gold therapy, penicillamine, phenytoin, sulfasalazine and zidovudine.

Drugs can cause blood dyscrasias by acting at different stages of haemopoiesis from the stem cell through to the mature cells – red cells, white cells and platelets. Aplastic anaemia, agranulocytosis and thrombocytopenia are blood dyscrasias that can occur.

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