Medicine overdose is widely understood in the context of taking higher than the medically recommended dose of medicine to harm oneself or “get high”.
In addition, illicit drugs are commonly known to be associated with overdose. However, overdose can also be accidental, occurring with the use of either a prescription or over-the-counter medicines.
Medicine overdose is considered accidental if one unknowingly takes a higher quantity than the recommended dose of a medicine.
An individual can also experience an overdose from taking certain medicines with food or beverages due to interactions. This results in high blood levels of medicine, which can cause toxicity.
Accidental overdose is also common in young children or adults with impaired mental abilities by taking medication left within their reach.
Causes of overdose
Forgotten administration instructions: Overdose can occur if one does not follow the administration instruction provided by their doctor or pharmacist; hence, they may end up taking more than what has been recommended. In addition, it can occur when one does not properly read the package insert or labelling of the medicines.
Using similar medicines: Overdose can also occur when taking more than one medicine containing a similar active ingredient. For example, two cold and flu medicines with different brand names may contain the same active ingredients, and this can result in one taking double the recommended dose if taken together. Even if the active ingredients are not exactly the same, but are from similar pharmacological classes, concomitant use can result in synergistic effects, therefore getting an effect greater than each medicine separately.
Incorrect use of measuring devices: Accidental overdose can also occur if one uses the wrong measuring device to administer medicine, for example using a tablespoon instead of a medicine spoon. This is usually risky with medicines categorised as having a narrow therapeutic index, meaning the gap between the safe and toxic levels is very small, therefore it is easy to reach toxicity.
Interactions: Accidental overdose can also result from taking medicine with another medicine(s), food or beverage that causes its levels in the blood or site of action to rise. This can occur via different mechanisms, one of which is when medicine or food or beverage inhibits the breakdown or conversion (metabolism) of a medicine. Interactions with the disease are also possible, where for example in individuals with kidney impairment there is decreased clearance of certain medicines leading to their accumulation in the body and ultimately toxicity.
Consequences of overdose
The consequences of a medicine overdose depend on the type of medicine taken. Specific medicines can also affect specific organs.
Generally, in an overdose, the effects of the medicine may be a heightened level of the therapeutic effects seen with regular use. In an overdose, side effects become more noticeable, and other effects can take place, which would not occur with the use of recommended doses. These may manifest as changes in pulse rate, respiratory rate, and blood pressure, which can be life-threatening. Sleepiness, confusion and coma are common with some medicines when taken in overdose. Seizures may also occur as well as damage to organs such as the lungs and liver. Breathing may become rapid, slow, deep, or shallow. Abdominal pain, nausea, vomiting and diarrhoea are also possible results of overdose.
If an overdose is identified, one should seek medical attention immediately. Some medicines have antidotes that are used to reverse the effects of a medicine overdose. In addition, the medical team can manage the resultant adverse effects where possible.
Accidental overdose of a medicine can be prevented by:
Following the instructions provided by your pharmacist, doctor or nurse. Always refer to the label or package insert of the medicine, even if you have taken the medicine before.
Talking to your pharmacist or doctor about other medicines that you are already taking to avoid duplication of the same or similar medicines, as well as interactions.
Ensuring that one always measures the liquid medicines accurately with the specified measuring device.
Ensure that your medicines are stored safely and out of reach of children and individuals with mental impairment. It is also important to note that alcohol should not be taken with medicines.
When you are not sure about any medicine, contact or visit your nearest pharmacist, medical doctor or health facility for advice.
* Nadine Mouton and Anna Shimbulu are medicines information and safety pharmacists from Namibia Medicines Regulatory Council (NMRC).