Deliberate or unintentional consumption of potentially harmful substances
- Accidental ingestion more common in young children
- Drug overdose more common in females
- Alcohol and drug abuse are risk factors
- Genetics is not a significant factor
In England, about 100,000 people attended hospital for treatment for poisoning in 2007. Most accidental poisonings occur in children under the age of 5, and many are preventable (see Home safety and health). However, poisoning in adults is commonly the result of a deliberate overdose (see Attempted suicide and suicide). Women are more likely than men to take a drug overdose.
Some substances, such as household bleach, are harmful regardless of how much is ingested. Prescribed drugs, such as sleeping drugs, usually cause harm only if the recommended dose is exceeded. Illegal substances, such as heroin, can have unpredictable effects, depending partly on the amount taken and on the person’s susceptibility to the drug (see Drugs and health).
What are the symptoms?
The symptoms vary from mild to severe. They may develop immediately or over a number of days. Some common general symptoms include:
Nausea and vomiting.
Shortness of breath.
Eventually, loss of consciousness.
There may also be local symptoms, such as burns in the mouth after swallowing caustic substances.
An overdose of certain drugs, such as tricyclic antidepressants (see Antidepressant drugs), can disturb the action of the heart and result in an irregular heart rhythm (see Arrhythmias) and sometimes a feeling of faintness. In some cases, an arrhythmia may even lead to cardiac arrest. Overdose of an opium-based drug, such as heroin, causes a reduction in breathing rate, which may be life-threatening. An overdose of some substances may also damage the liver and kidneys. For example, liver failure may result from an overdose of paracetamol (see Painkillers). Rarely, ingestion of certain poisons can cause a severe allergic reaction (see Anaphylaxis).
What can I do?
If the casualty is unconscious or loses consciousness, call an ambulance. Find a trained first-aider to monitor the person’s breathing and pulse rate and give emergency first aid as necessary. Stay with the casualty until help arrives.
Even if there are no symptoms and the quantity of poison ingested is small, always consult your doctor or poison centre for advice. Collect as much information as possible, including bottles or containers and remains of the substance that has been taken. If vomiting has occurred, collect a sample for analysis by the doctor. If the person is unconscious or reluctant to talk, you may be needed to provide vital information. Do not give the person anything to drink or try to induce vomiting unless instructed to do so by a medical professional.
What might the doctor do?
The doctor needs to know what has been taken and when. He or she will examine the person and, if a drug overdose has been taken, will arrange for blood tests to measure drug levels in the circulation. Other body fluids, such as vomit, may be analysed.
In some cases, admission to an intensive therapy unit for monitoring and treatment may be required. If tricyclic antidepressants have been taken, the heart rhythm is monitored to detect any abnormalities. After a paracetamol overdose, blood tests are carried out to look for signs of liver damage.
Various methods may be used to try to eliminate the ingested substance from the digestive tract and to prevent it from being absorbed into the circulation. If the person is conscious, a tube may be passed through the mouth into the stomach to wash out the stomach contents with sterile water or a saline solution, a procedure known as gastric lavage. If the person is unconscious, another tube is passed into the windpipe to prevent liquid from entering the lungs while gastric lavage is being performed.
Alternatively, activated charcoal may be given orally. The toxic substance binds to the charcoal in the digestive tract and is then passed out in the faeces. If very high levels of a toxic substance are present in the circulation, elimination can be increased by filtering the blood (see Dialysis). Some substances can be inactivated by giving a specific antidote. For example, naloxone may be given for an opium-based overdose.
Complications are usually treated as they arise. For example, antiarrhythmic drugs can be prescribed for an irregular heartbeat. If breathing difficulties are severe, mechanical ventilation may eventually be required.
If an overdose was taken deliberately, a psychiatric assessment will be carried out when the person is stable.
What is the prognosis?
Although poisoning may be fatal, most cases are treated successfully. However, in some cases, there may be permanent damage, such as liver damage following an overdose of paracetamol.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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