One in Three Older Hospital Patients Gets a Wrong Blood Thinner Dose, Study Finds

Every day, millions of older adults take direct oral anticoagulants, or DOACs, the modern blood thinners that have largely replaced warfarin for preventing strokes in atrial fibrillation and for treating dangerous clots. These drugs are powerful and convenient, but their safety depends entirely on getting the dose right. A new prospective multicenter study from France suggests that, even in 2023, hospitals are still getting it wrong for roughly one in three older patients on admission, and one in four at discharge.

The study, published in BMC Geriatrics by a team of hospital pharmacists and pharmacoepidemiologists affiliated with Assistance Publique–Hôpitaux de Paris and Paris-Saclay University, set out to measure how often DOAC prescriptions in hospitalized older adults deviated from European Society of Cardiology (ESC) guidelines, and whether the situation had improved since a comparable assessment in 2018. The answer, in short, is that it had not.

Between November 2022 and May 2023, the researchers consecutively enrolled older adults who were already taking a DOAC before admission and who stayed in one of three French university hospitals for more than 24 hours. The participating departments spanned cardiology, internal medicine, post-emergency care, and acute geriatrics, giving a broad picture of real-world prescribing across the acute care pathway. In total, 536 patients were eligible, with a mean age of 84.1 years and a slight majority of women; 421 patients formed the primary analysis cohort.

The pharmacological profile of the cohort reflected current practice. Apixaban dominated, accounting for 70.1 percent of prescriptions, and atrial fibrillation was the indication in 83.6 percent of cases. This matters because apixaban, like all DOACs, has a narrow therapeutic window whose appropriateness hinges on patient-specific factors: renal function, age, body weight, and the indication being treated. Unlike warfarin, which is monitored with routine blood tests, DOAC dosing is fixed at prescription time, so an error at the moment of prescribing persists silently until harm occurs.

Using ESC guidelines as the benchmark, the team classified prescriptions as appropriate or inappropriate at two critical moments: hospital admission and hospital discharge. On admission, 32.0 percent of prescriptions were judged inappropriate. By discharge, the figure had fallen to 24.9 percent, a statistically significant improvement (p = 0.004), suggesting that the hospital stay does correct some errors, but leaves a substantial fraction of patients heading home with potentially unsafe anticoagulation.

The consequences of such errors are not abstract. An excessive dose in a frail 85-year-old with declining kidney function increases the risk of major bleeding, including intracranial hemorrhage. An insufficient dose, conversely, can mean therapeutic failure, allowing a stroke or systemic embolism to occur despite the patient dutifully taking their medication. In older patients with polypharmacy, where DOACs interact with other drugs and renal clearance is often reduced, the margin for error shrinks further, which is why inappropriate prescribing is considered a major patient safety concern in geriatric care.

To understand who was most at risk, the researchers used logistic regression to identify predictive factors for inappropriate prescribing. Two variables stood out at admission: age over 80 years nearly doubled the odds of an inappropriate prescription (odds ratio 1.80, 95 percent confidence interval 1.20–2.72), and elevated serum creatinine above 133 µmol/L, a marker of impaired kidney function, similarly raised the odds (OR 1.84, 95 percent CI 1.13–2.98). At discharge, age over 80 remained a strong risk factor (OR 2.71, 95 percent CI 1.63–4.61), while a body weight below 60 kilograms was unexpectedly protective (OR 0.42, 95 percent CI 0.25–0.69), possibly because clinicians scrutinize low-weight patients more carefully when selecting doses.

The renal connection deserves particular emphasis. DOACs are cleared substantially by the kidneys, and estimates of glomerular filtration rate in older adults vary depending on the formula used, whether Cockcroft–Gault, MDRD, or CKD-EPI. The study’s authors assessed prescriptions against the Summary of Product Characteristics for each molecule, which specify dose reductions based on renal function, age, and weight. When kidney function is overestimated, or when a hospitalization changes a patient’s renal status without the prescription being adjusted, the fixed daily dose can quickly become dangerous. Advanced age and impaired renal function, the two risk factors identified here, are precisely the conditions that make this pharmacokinetic tightrope hardest to walk.

Perhaps the most sobering finding is the comparison with 2018. Using chi-squared tests, the team compared their results with data collected five years earlier and found no significant changes. Despite growing awareness of DOAC dosing pitfalls, updated guidelines, and the expansion of clinical pharmacy services in French hospitals, the rate of inappropriate prescribing in this vulnerable population has remained essentially flat. The authors conclude that further efforts to optimize DOAC prescribing are warranted, and they point toward concrete interventions: pharmacist-led medication reviews at admission and discharge, and integrated prescribing tools embedded in electronic medical records that would automatically flag doses inconsistent with renal function, age, and weight.

The study has the strengths and limits of its design. As a prospective observational study, it captures real prescribing behavior rather than idealized trial conditions, and its multicenter scope across four department types strengthens generalizability within the French hospital system. But it also reflects a single country’s practice in a single year, and appropriateness was defined by ESC guidelines rather than patient-specific outcomes, so the findings measure guideline concordance rather than directly measured harm. Even so, the message is clear and actionable: the transition points of hospital care, admission and discharge, remain moments where older patients on DOACs are at elevated risk of a prescribing error, and after years of stagnation, systematic medication reconciliation and decision support may be the tools that finally bend the curve.

Subject of Research: Appropriateness of direct oral anticoagulant prescribing in hospitalized older adults

Article Title: Appropriateness prescriptions of direct oral anticoagulants in hospital in 2023 in the older population: a prospective observational multicenter study

Article References: Rodier, T., Gibert, A., Lepors, A., Fernandez, C., Hindlet, P., Savoldelli, V., & Schwab, C. (2026). Appropriateness prescriptions of direct oral anticoagulants in hospital in 2023 in the older population: a prospective observational multicenter study. BMC Geriatrics. https://doi.org/10.1186/s12877-026-08330-9

Image Credits: AI Generated

DOI: 10.1186/s12877-026-08330-9

Keywords: DOACs, anticoagulants, older adults, prescribing appropriateness, medication safety, atrial fibrillation, apixaban, renal function, polypharmacy, hospital discharge, pharmacist-led medication review, geriatrics