It can be confusing when you see the terms adverse reactions and side effects. Do they mean the same thing? Sometimes, but not always. Adverse Drug Reactions and Clinical Pharmacology - Learn about from the Merck Manuals - Medical Professional Version. An adverse drug reaction (ADR) is an injury caused by taking medication. ADRs may occur following a single dose or prolonged administration of a drug or.
Incidence and severity of adverse drug reactions vary by patient characteristics eg, age, sex, ethnicity, coexisting disorders, genetic or geographic factors and by drug factors eg, type of drug, administration route, treatment duration, dosage, bioavailability.
Incidence is higher with advanced age and polypharmacy. The contribution of prescribing and adherence errors to the incidence of ADRs is unclear. Adverse drug events in U. Agency for Healthcare Research and Quality. Most adverse drug reactions are dose-related; others are allergic or idiosyncratic. Dose-related ADRs are particularly a concern when drugs have a narrow therapeutic index eg, hemorrhage with oral anticoagulants.
ADRs may result from decreased drug clearance in patients with impaired renal or hepatic function or from drug-drug interactions. Allergic ADRs are not dose-related and require prior exposure. Allergies develop when a drug acts as an antigen or allergen. After a patient is sensitized, subsequent exposure to the drug produces one of several different types of allergic reaction. Clinical history and appropriate skin tests can sometimes help predict allergic ADRs. They occur in a small percentage of patients given a drug.
Idiosyncrasy is an imprecise term that has been defined as a genetically determined abnormal response to a drug, but not all idiosyncratic reactions have a pharmacogenetic cause. The term may become obsolete as specific mechanisms of ADRs become known. Adverse drug reactions are usually classified as mild, moderate, severe, or lethal see table Classification of Adverse Drug Reactions [ADRs].
Severe or lethal ADRs may be specifically mentioned in black box warnings in the physician prescribing information provided by the manufacturer. Symptoms and signs may manifest soon after the first dose or only after chronic use. They may obviously result from drug use or be too subtle to identify as drug-related. In the elderly, subtle ADRs can cause functional deterioration, changes in mental status, failure to thrive, loss of appetite, confusion, and depression.
A change in treatment eg, modified dosage, addition of a drug , but not necessarily discontinuation of the drug, is required; hospitalization may be prolonged, or specific treatment may be required. Allergic ADRs typically occur soon after a drug is taken but generally do not occur after the first dose; typically, they occur when the drug is given after an initial exposure.
Symptoms include itching, rash, fixed-drug eruption, upper or lower airway edema with difficulty breathing, and hypotension. Symptoms that occur soon after a drug is taken are often easily connected with use of a drug. However, diagnosing symptoms due to chronic drug use requires a significant level of suspicion and is often complicated. Stopping a drug is sometimes necessary but is difficult if the drug is essential and does not have an acceptable substitute.
When proof of the relationship between drug and symptoms is important, rechallenge should be considered, except in the case of serious allergic reactions. Only through such reporting can unexpected ADRs be identified and investigated. Patients should be given information about which drugs and drug-classes to avoid and encouraged to share their drug allergy status. If a drug allergy is suspected, consider stopping the suspected drug and advising the patient or carer to avoid this drug in future.
Symptoms of the acute reaction should be treated, in hospital if severe. Patients presenting with a suspected anaphylactic reaction, or a severe or non-immediate cutaneous reaction, should be referred to a specialist drug allergy service.
Patients presenting with a suspected drug allergic reaction or anaphylaxis to NSAIDs, and local and general anaesthetics may also need to be referred to a specialist drug allergy service, e.
Patients presenting with a suspected drug allergic reaction or anaphylaxis associated with beta-lactam antibiotics should be referred to a specialist drug allergy service if their disease or condition can only be treated by a beta-lactam antibiotic or they are likely to need beta-lactam antibiotics frequently in the future e. For further information see Drug allergy: Drug-induced disorders of the mouth may be due to a local action on the mouth or to a systemic effect manifested by oral changes.
Medicaments left in contact with or applied directly to the oral mucosa can lead to inflammation or ulceration; the possibility of allergy should also be borne in mind.
Aspirin tablets allowed to dissolve in the sulcus for the treatment of toothache can lead to a white patch followed by ulceration. Flavouring agents, particularly essential oils , may sensitise the skin, but mucosal swelling is not usually prominent. The oral mucosa is particularly vulnerable to ulceration in patients treated with cytotoxic drugs, e. Other drugs capable of causing oral ulceration include ACE inhibitors, gold, nicorandil , NSAIDs, pancreatin , penicillamine , proguanil hydrochloride , and protease inhibitors.
Erythema multiforme or Stevens-Johnson syndrome may follow the use of a wide range of drugs including antibacterials, antiretrovirals, sulfonamide derivatives, and anticonvulsants ; the oral mucosa may be extensively ulcerated, with characteristic target lesions on the skin.
Oral lesions of toxic epidermal necrolysis have been reported with a similar range of drugs. Candidiasis can complicate treatment with antibacterials and immunosuppressants and is an occasional side-effect of corticosteroid inhalers.
Brown staining of the teeth frequently follows the use of chlorhexidine mouthwash, spray or gel, but can readily be removed by polishing. Iron salts in liquid form can stain the enamel black. Superficial staining has been reported rarely with co-amoxiclav suspension. Intrinsic staining of the teeth is most commonly caused by tetracyclines. They will affect the teeth if given at any time from about the fourth month in utero until the age of twelve years; they are contra-indicated during pregnancy, in breast-feeding women, and in children under 12 years.
All tetracyclines can cause permanent, unsightly staining in children, the colour varying from yellow to grey. All patients receiving bisphosphonates should have a dental check-up and any necessary remedial work should be performed before bisphosphonate treatment, or as soon as possible after starting treatment.
Patients with cancer receiving bevacizumab or sunitinib may also be at risk of osteonecrosis of the jaw. Gingival overgrowth gingival hyperplasia is a side-effect of phenytoin and sometimes of ciclosporin or of nifedipine and some other calcium-channel blockers. Thrombocytopenia may be drug related and may cause bleeding at the gingival margins, which may be spontaneous or may follow mild trauma such as toothbrushing.
The most common effect that drugs have on the salivary glands is to reduce flow xerostomia. Patients with a persistently dry mouth may have poor oral hygiene; they are at an increased risk of dental caries and oral infections particularly candidiasis.
Many drugs have been implicated in xerostomia, particularly antimuscarinics anticholinergics , antidepressants including tricyclic antidepressants, and selective serotonin re-uptake inhibitors , alpha-blockers, antihistamines, antipsychotics, baclofen , bupropion hydrochloride , clonidine hydrochloride , 5HT 1 agonists, opioids , and tizanidine.
Excessive use of diuretics can also result in xerostomia. Pain in the salivary glands has been reported with some antihypertensives e. Swelling of the salivary glands can occur with iodides, antithyroid drugs, phenothiazines, and sulfonamides. There can be decreased taste acuity or alteration in taste sensation.
Many drugs are implicated, including amiodarone hydrochloride , calcitonin, ACE inhibitors , carbimazole , clarithromycin , gold , griseofulvin , lithium salts , metformin hydrochloride , metronidazole , penicillamine , phenindione , propafenone hydrochloride , protease inhibitors , terbinafine , and zopiclone. During the manufacture or distribution of a medicine an error or accident may occur whereby the finished product does not conform to its specification.
While such a defect may impair the therapeutic effect of the product and could adversely affect the health of a patient, it should not be confused with an Adverse Drug Reaction where the product conforms to its specification. The Defective Medicines Report Centre assists with the investigation of problems arising from licensed medicinal products thought to be defective and co-ordinates any necessary protective action.
Reports on suspect defective medicinal products should include the brand or the non-proprietary name, the name of the manufacturer or supplier, the strength and dosage form of the product, the product licence number, the batch number or numbers of the product, the nature of the defect, and an account of any action already taken in consequence.
The Centre can be contacted at:. Home Medicines guidance Adverse reactions to drugs. Yellow card scheme Any drug may produce unwanted or unexpected adverse reactions.
Send Yellow Cards to: The following Yellow Card Centres can be contacted for further information: Self-reporting Patients and their carers can also report suspected adverse drug reactions to the MHRA. Newer drugs and vaccines Only limited information is available from clinical trials on the safety of new medicines. Established drugs and vaccines Healthcare professionals and coroners are asked to report all suspected reactions to established drugs including over-the-counter, herbal, and unlicensed medicines and medicines used off-label and vaccines that are serious, medically significant, or result in harm.
Medication errors Adverse drug reactions where harm occurs as a result of a medication error are reportable as a Yellow Card or through the local risk management systems into the National Reporting and Learning System NRLS. Adverse reactions to medical devices Suspected adverse reactions to medical devices including dental or surgical materials, intra-uterine devices, and contact lens fluids should be reported.
Side-effects in the BNF The BNF includes clinically relevant side-effects for most drugs; an exhaustive list is not included for drugs that are used by specialists e.
In the product literature the frequency of side-effects is generally described as follows: Description of the frequency of side-effects Very common greater than 1 in 10 Common 1 in to 1 in 10 Uncommon [formerly 'less commonly' in BNF publications] 1 in to 1 in Rare 1 in 10 to 1 in Very rare less than 1 in 10 Frequency not known frequency is not defined by product literature or the side-effect has been reported from post-marketing surveillance data For consistency, the terms used to describe side-effects are standardised using a defined vocabulary across all of the drug monographs in the BNF e.
Special problems Delayed drug effects Some reactions e. The elderly Particular vigilance is required to identify adverse reactions in the elderly.
Congenital abnormalities When an infant is born with a congenital abnormality or there is a malformed aborted fetus doctors are asked to consider whether this might be an adverse reaction to a drug and to report all drugs including self-medication taken during pregnancy.
Children Particular vigilance is required to identify and report adverse reactions in children, including those resulting from the unlicensed use of medicines; all suspected reactions should be reported directly to the MHRA through the Yellow Card Scheme see also Adverse Drug Reactions in Children.
Prevention of adverse reactions Adverse reactions may be prevented as follows: If the patient is pregnant do not use a drug unless the need for it is imperative; allergy and idiosyncrasy are important causes of adverse drug reactions. Ask if the patient had previous reactions to the drug or formulation; ask if the patient is already taking other drugs including self-medication drugs, health supplements, complementary and alternative therapies; interactions may occur; age and hepatic or renal disease may alter the metabolism or excretion of drugs, so that much smaller doses may be needed.
Genetic factors may also be responsible for variations in metabolism, and therefore for the adverse effect of the drug; notably of isoniazid and the tricyclic antidepressants; prescribe as few drugs as possible and give very clear instructions to the elderly or any patient likely to misunderstand complicated instructions; whenever possible use a familiar drug; with a new drug, be particularly alert for adverse reactions or unexpected events; consider if excipients e.
If the reaction is minor, a trial of an alternative formulation of the same drug may be considered before abandoning the drug; warn the patient if serious adverse reactions are liable to occur. Drug allergy suspected or confirmed Suspected drug allergy is any reaction caused by a drug with clinical features compatible with an immunological mechanism. A reaction is more likely to be caused by drug allergy if: The reaction occurred while the patient was being treated with the drug, or The drug is known to cause this pattern of reaction, or The patient has had a similar reaction to the same drug or drug-class previously.
The following signs, allergic patterns and timing of onset can be used to help decide whether to suspect drug allergy:
Medsafe: New Zealand Medicines and Medical Devices Safety Authority
An adverse reaction to a drug has been defined as any noxious or unintended reaction to a drug that is administered in standard doses by the. Adverse reactions to medicines include side effects, reactions between two or more medicines or herbal supplements, reactions between a food and a medicine. Adverse reaction: In pharmacology, any unexpected or dangerous reaction to a drug. An unwanted effect caused by the administration of a drug. The onset of.