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Information for healthcare professionals:

Adverse Reactions to Drugs

Any drug may produce unwanted or unexpected adverse reactions (ADRs). Rapid detection and recording of these is of vital importance. All healthcare professionals and patients are therefore urged to help by reporting suspected ADRs directly to MHRA.

Suspected adverse reactions to any therapeutic agent should be reported, including drugs (self-medication as well as those prescribed), blood products, vaccines, rediographic contrast media and herbal products.

Suspected ADRs can be reported via the electronic Yellow Card, which can be found at

Alternatively, prepaid Yellow Cards for reporting are available from MHRA, CHM, Freepost, London SW8 5BR.

A 24-hour Freephone service is available to all parts of the UK for advice and information on suspected ADRs: contact the National Yellow Card Information Service at the MHRA on
0800 731 6789
. Outside office hours a telephone answering machine will take messages.

The following centres may follow up reports:

Yellow Card Centre Mersey
Freepost, Liverpool L3 3AB. Tel: 0151 794 8206

Yelllow Card Centre Wales
Freepost, Cardiff CF4 1ZZ. Tel: 029 2074 4181

Yellow Card Centre Scotland
CARDS, Freepost NAT3271, Edinburgh EH16 4BR. Tel: 0131 242 2919

Yellow Card Centre Northern & Yorkshire
Freepost 1085, Newcastle upon Tyne NE1 1BR. Tel: 0191 232 1525

Yellow Card Centre West Midlands
Freepost SW2991, Birmingham B18 7BR. Tel: 0121 507 5672


Patients or their representatives can report directly to the MHRA using the online system. Alternatviely, patient Yellow Cards are available from pharmacies or can be downloaded from the MHRA's website ( where more detailed information on reporting is available on 0808 100 3352.

Doctors, dentists, coroners and pharmacists are asked to report all suspected reactions (ie, any adverse or any unexpected event, however minor, which could conceivably be attributed to the drug.) Reports should be made despite uncertainty about a causal relationship, irrespective of whether the reaction is well recognised, and even if other drugs have been given concurrently.

Doctors, dentists, coroners and pharmacists are asked to report all serious suspected reactions, including those which are fatal, life threatening, disabling, incapacitating, or which result in or prolonged hospitalisation; they should be reported even if the effect is well recognised.

Examples include anaphylaxis, blood disorders, endocrine disturbances, effects on fertility, haemorrhage from any site, renal impairment, jaundice, ophthalmic disorders, severe CNS effects, severe skin reactions, reactions in pregnant women and any drug interactions.

Reports of serious ADRs are required to enable risk/benefit ratios to be compared with other drugs of a similar class. For established drugs, doctors are asked not to report well known, relatively minor side effects, such as dry mouth with tricyclic antidepressants, constipation with opicids, or nausea with digoxin.

Delayed drug effects
Some reactions (e.g., cancers, chloroquine retinopathy and retroperitoneal fibrosis) may become manifest months or years after drug exposure. Any suspicion of such an association should be reported.

The elderly
Doctors are asked to be particularly alert to 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.

Particular vigilance is required to identify adverse reactions in children, including those due to the unlicensed use of medicines; all suspected reactions should be reported.

Adverse reactions may be prevented as follows:

  1. Never use any drug without a good indication. In pregnant women do not use a drug unless the need is imperative.
  2. Allergy and idiosyncrasy are important causes of ADRs. Ask if the patient has had previous reactions.
  3. Ask if the patient is already taking other drugs including self-medication; interactions may occur.
  4. 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, notably of isoniazid and the tricyclic antidepressants.
  5. Prescribe as few drugs as possible and give very clear instructions to the elderly or any patient likely to misunderstand complicated instructions.
  6. When possible use a familiar drug. With a new drug be particularly alert for ADRs or unexpected events.
  7. If serious ADRs are liable to occur warn the patient.
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Copyright PAGB (Proprietary Association of Great Britain) - 2003 - All Rights Reserved. PAGB has made every effort to ensure the information contained in this site is as accurate and up to date as possible. However you should always read the label before you take a medicine for the first time as it is important that medicines are used correctly and according to the instructions. All OTC medicines are effective and safe when used properly. None of the information given in this directory should be construed to be advice or recommendation of a particular medicine. PAGB cannot accept responsibility for errors or omissions.