From cough syrups to laxatives, there are several medications available over the counter that can give a false sense of security and make patients ignore the risks of taking excessive doses.
Many people assume that over-the-counter medications are inherently safe. After all, if you can buy something in a supermarket or a pharmacy, how dangerous can it be?
The reality is more complex. Several commonly used over-the-counter medications have a real risk of addictionmisuse or harm when taken in higher doses than recommended, for longer than necessary or for the wrong reasons. Here are five medications worth knowing about.
1. Codeine-based painkillers
Codeine is an opioid used to treat mild to moderate pain and, in some formulations, to suppress coughs. It is generally sold without a prescription combined with ibuprofen or paracetamol. After ingestion, the body converts codeine into morphine, which produces its analgesic effects.
Common side effects include drowsiness, constipation, nausea and dizziness. At higher doses, codeine can slow breathing and impair coordination. Some people are particularly vulnerable. Ultra-rapid metabolizers have a genetic variant that causes them to convert codeine into morphine much faster than normal. This characteristic is more common in people of North African, Middle Eastern and Oceanian origin and can lead to dangerous side effects, even at standard doses.
With repeated use, the body may also develop tolerance to codeine, meaning that the same dose no longer provides the same relief. This process, known as tolerance, occurs as the brain’s opioid receptors adapt to the drug. People may then increase the dose, increasing the risk of physical dependence. Sudden cessation of use may cause withdrawal symptoms such as anxiety, restlessness, sweating, and sleep problems.
To reduce these risks, codeine should be used for as short a time as possible. In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) limits packaging sizes to 32 tablets and recommends that over-the-counter products be used for no more than three days.
2. Decongestants
Decongestants are available in tablets containing pseudoephedrine or in sprays and nasal drops, such as xylometazoline and oxymetazoline. Both work by narrowing the blood vessels in the nasal passages, reducing swelling and mucus.
Excessive use of nasal sprays can lead to bouncing congestion, medically known as medicinal rhinitis. Over time, the medication becomes less effective, a phenomenon called tachyphylaxis. This can trap people in a cycle of increasing use, worsening congestion, and dependence.
Long-term excessive use can damage the lining of the nosecausing dryness, nosebleeds and, in severe cases, perforation of the nasal septum. Many users also develop psychological dependence on the spray. Most guidelines recommend limiting use to three to five days.
Pseudoephedrine also has mild stimulant effects. Although the evidence on improving athletic performance is controversial, its stimulant properties make it appear on the list of substances prohibited in competitions. It is also used illicitly to produce methamphetamine, which is why strict sales controls remain in place following a 2016 review.
3. Sleeping tablets
Promethazine and diphenhydramine are sedating antihistamines sold as short-term sleep aids. Recent research has linked sedative antihistamines to increase in the number of deathswhich has led to calls for a review of the way they are provided.
Promethazine can quickly lead to tolerance, which means they are higher doses required to achieve the same effect. Some long-term users report severe rebound insomnia when they try to stop.
It is also used recreationally in “purple drinks”, a mixture of cough syrup containing promethazine and soft drinks. This combination can cause extreme sedation, slow breathing and serious harm.
4. Cough syrups
Dextromethorphan (DXM) is a common cough suppressant. A 2021 review found it was the most frequently misused over-the-counter medication among those studied. At high doses, blocks NMDA receptors in the brainwhich can cause dissociative effects similar to those of ketamine. Although it is safe at recommended doses, its psychoactive effects have raised concerns about misuse.
5. Laxatives
Stimulant laxatives stimulate the intestinal muscles to move stool. They are often misused by people with eating disorders, athletes in weight-restricted sports or those who believe that daily bowel movements are essential. In fact, constipation is generally defined as less than three bowel movements per week.
Research shows that stimulant laxatives do not prevent calorie absorption, despite common myths. Instead, misuse may cause dehydrationelectrolyte imbalance and long-term damage to the intestine, with serious effects on the heart and kidneys in severe cases. In 2020, the MHRA introduced new rules on pack sizes and warnings.
The common link between these medications is not that they are inherently dangerous, but that their risks are often underestimated. The availability of non-prescription medicines can create a false sense of security, especially when they are purchased online without professional advice. Although regulatory bodies have taken action, research suggests that misuse persists.
Over-the-counter medications are not always risk-free, and greater awareness could help keep these medications helpful rather than harmful.
