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January 3, 2022updated 07 Jan 2022 6:16am

The challenges of multiple drugs safety reporting

Pharmacovigilance of a single drug is one thing, but investigating an adverse event in case of polypharmacy is even more complex.

By Abi Millar

Polypharmacy – typically defined as taking five or more medications every day – has become a staple of many people’s lives, with many older people in particular being prescribed a cocktail of different pills.

While estimates for polypharmacy vary, there is broad agreement that the practice is on the rise. According to one UK-based study, the number of people aged over 65 taking five or more medicines (prescription and over the counter) has almost quadrupled over the past two decades, from 12% to 49%. Another study, focusing on older adults in care homes, found that 91% are taking more than five medications, and 65% are taking more than 10.

Access to medicines has undoubtedly saved many lives, while alleviating the burden of symptoms. However, polypharmacy can create problems in its own right. As Elen Jones, director for Wales at the Royal Pharmaceutical Society, explains, prescriptions can tend to get longer and longer over time as a person needs additional medical care. Medicines often remain on the prescription even once they’re no longer required.

“As people are living longer lives with complex and multiple conditions, they are prescribed an increasing number of medicines,” she says. “This increases the risk of side effects and interactions between medicines and leads to poor health, a lower quality of life and costly, unnecessary admissions to hospital.”

In some cases, a person might be prescribed a drug to treat the side effects from a different drug, when taking steps to reduce the number of drugs might be more appropriate. In other cases, their healthcare might be fragmented, with different prescriptions coming from different specialists who don’t talk to each other. Situations of this kind tend to be correlated with worse outcomes.

The risk of drug-drug interactions

One of the biggest sticking points when it comes to polypharmacy is the risk of drug-drug interactions (DDIs). When two or more medicines are taken together, the interactions between them can sometimes impact on efficacy and safety. According to one estimate, DDIs may be responsible for 30% of adverse drug reactions (ADRs).

For instance, two drugs that share an active ingredient can cause an overdose, while blood-thinning drugs coupled with ibuprofen can increase the risk of a dangerous bleed. Certain drugs have even been pulled from the market because of the likelihood of DDIs, such as the hypertension drug mibefradil, which caused toxic interactions with 26 other medications.

The more medicines a person takes, the harder it can be to keep track of all the different possible interactions. This is especially true in cases where healthcare isn’t joined up or the patient isn’t forthcoming about what they’re taking.

Any medicine prescribed for a patient should only occur through a shared decision-making process where the risks and benefits are discussed.

“When a new medicine is prescribed, the prescriber must consider the desired outcomes for the issue being treated but also be aware of any interactions between the new medicine and any existing medicines,” says Jones. “The prescriber will use clinical guidance and reference sources such as the British National Formulary and Stockley’s Drug Interactions to help make the best decisions for their patients.”

When a new medicine is added to a patient’s regimen, the prescriber may need to monitor that person more intensely and adjust some of their existing doses. In the case of an over-the-counter drug, the pharmacist should check to see whether the patient is already taking medications.

“Any medicine prescribed for a patient should only occur through a shared decision-making process where the risks and benefits are discussed,” she says. “The role of pharmacists in reviewing people’s medicines and ensuring they are on the right medicines for their conditions is becoming increasingly important.”

Polypharmacy and pharmacovigilance

As and when there are adverse effects, it can be hard to know what caused them. Was it caused by drug X, drug Y, or an interaction between them? Compounding this problem, the symptoms caused by polypharmacy can often be interpreted as the normal signs of ageing – tiredness, digestive symptoms, confusion, depression and so forth.

While pharmacovigilance in this area isn’t always straightforward, the first step is to report any suspected ADRs no matter what has caused them. In the US, this means reporting to the FDA’s Adverse Event Reporting System, while in the UK it means reporting to the Medicines and Healthcare products Regulatory Agency through the Yellow Card Scheme.

“Any health professional who identifies or is made aware of the ADR should report it using the Yellow Card Scheme, and ensure appropriate communication with the rest of the team,” says Jones. “This should not be the sole responsibility of the prescriber. Patients can also report themselves.”

As well as mining pharmacovigilance data, researchers can apply their tools to the scientific literature and even social media.

Once ADRs are recorded in the system, there is scope to use data mining tools to better understand what caused them. Using new informatics-driven approaches, data scientists can sift through reams of data to flag up possible drug-drug interactions. As well as mining pharmacovigilance data, researchers can apply their tools to the scientific literature and even social media.

Although these approaches do hold promise for better understanding DDIs, it simply isn’t feasible to evaluate all possible drug combinations. On top of that, older people tend to be underrepresented in scientific studies. This means the data may not accurately represent the way these drugs are used in the population. For that reason, the risks of excessive polypharmacy need to be tackled in their own right.

“Systems across health and social care should identify individuals who are most at risk from harm from polypharmacy,” says Jones. “Those taking multiple medicines, taking high-risk medicines and those who are not coping well with their medicines should then receive a structured, holistic medication review by a pharmacist, working with the multidisciplinary team.”

Evidently, there is a place for better safety reporting with appropriate data mining tools as well as a reduction in problematic polypharmacy more generally. Done appropriately, polypharmacy can extend life expectancy and improve quality of life – but it’s important to consider the harms to benefits ratio. With patients being prescribed ever more drugs, it will be critical to address this challenge from all angles.

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