Bridging the gap: new oral anticoagulants in elderly inpatients

Walking through the corridors of any large Australian tertiary hospital, the pattern is unmistakable. More than half the beds are occupied by patients over 65, many of them admitted with atrial fibrillation, venous thromboembolism, or post-operative complications that demand anticoagulation. The rise of non-vitamin K oral anticoagulants has rewritten the playbook, yet busy registrars and consultants still report a gnawing uncertainty when starting a new oral anticoagulant in an 86-year-old with a creatinine clearance of 38 mL/min and a stack of home medications. Sessions at Hospital Medicine 2017 tackled exactly this clinical anxiety, and the lessons translate well to the realities of Australian wards.

Australian practice sits inside a tightly regulated pharmaceutical landscape. The Therapeutic Goods Administration approves each agent, and the Pharmaceutical Benefits Scheme determines who can access subsidised therapy. Apixaban, rivaroxaban, dabigatran and edoxaban are all PBS-listed for specific indications, but the authority-script criteria often dictate the drug of choice long before any clinical nuance is considered. Layer on top the cultural shorthand of the ward round — a quick "no worries, we'll sort her anticoagulation out this arvo" — and the gap between published evidence and bedside decision-making becomes a practical concern, not an academic one.

Why elderly inpatients deserve a separate conversation

The over-75s are not simply older versions of the average trial participant. Reduced lean body mass, declining hepatic metabolism, and a glomerular filtration rate that can swing by 20 per cent during a single admission mean that pharmacokinetics behave unpredictably. Polypharmacy is the rule rather than the exception: a patient at Royal Prince Alfred may arrive on 11 regular medications, including amiodarone, verapamil, or a macrolide antibiotic, each capable of shifting NOAC exposure through P-glycoprotein or CYP3A4 pathways. Falls risk compounds the bleeding equation, and cognitive impairment can undermine adherence once the patient is back in their own home.

Australian prevalence data reinforces why this matters. The Heart Foundation estimates more than 5 per cent of Australians over 65 live with atrial fibrillation, and that figure climbs steeply past 80. Each hospital admission for an older patient is therefore a chance to get the anticoagulation plan right — or to lock in problems that will surface in the emergency department weeks later.

The table is a starting point, not a substitute for the product information. CrCl values are calculated using the Cockcroft-Gault equation, which still matters more than eGFR for NOAC dosing in older Australians.

Pharmacokinetics tailored to the older patient

Renal function is the single most important variable, and it is also the most often misjudged. Serum creatinine alone can be misleading in a frail 78-year-old whose muscle mass has dwindled; a "normal" creatinine of 95 µmol/L may correspond to a CrCl closer to 35 mL/min. Hospitals like The Alfred in Melbourne and Princess Alexandra in Brisbane have moved to embedded pharmacy-led NOAC dose reviews within 24 hours of admission, partly because early audits caught dose errors in nearly one in five elderly inpatients. The same audits consistently found that prescribers defaulted to the higher dose listed in the trials rather than the reduced dose triggered by the label.

Hepatic impairment is rarer but worth flagging. Child-Pugh B cirrhosis roughly halves the clearance of apixaban and halves rivaroxaban exposure; dabigatran is less affected because it relies on renal excretion. Drug-drug interactions deserve a quick scan: verapamil and diltiazem can lift dabigatran levels by up to 50 per cent, while rifampicin and carbamazepine — sometimes started for new diagnoses during an admission — slash exposure across the class. A simple medication reconciliation against the Australian Medicines Handbook takes minutes and prevents months of avoidable thromboembolism.

Bleeding risk, reversal, and the handover problem

Bleeding is the trade every anticoagulant story carries. HAS-BLED remains useful as a conversation tool, even if its predictive power is modest in the very elderly. What matters more at the bedside is whether a reversal strategy exists in real time. Idarucizumab is PBS-listed and held in many metropolitan emergency departments, allowing rapid dabigatran reversal for life-threatening haemorrhage or urgent surgery. Andexanet alfa has been the talk of international meetings, but its Australian availability at the time of Hospital Medicine 2017 was via Special Access Scheme only — worth documenting in the notes so the on-call team is not caught short at 2 am.

The handover between teams is where the plan often frays. A patient started on apixaban in the cardiology unit can be transferred to a general medical team overnight, and the next morning's ward round may have no record of the dosing criteria or the planned duration of therapy. Embedding structured handoff strategies for every anticoagulated patient — including the trigger for dose reduction and the follow-up plan — reduces both under- and over-anticoagulation. A handful of Australian sites now mandate an "anticoagulation passport" stapled into the bedside folder, with the brand, dose, indication, renal function, and reversal agent clearly noted.

Translating evidence into Australian wards

The Australian context shapes which NOAC ends up on the drug chart. PBS authority criteria for non-valvular atrial fibrillation require a CHA₂DS₂-VASc score of at least 2 in males or 3 in females, and prescribers must tick the appropriate box. Some hospital formularies favour apixaban because of its favourable bleeding profile in older subgroups from the ARISTOTLE trial, while others allow clinicians free choice once criteria are satisfied. Private hospital systems in Australia often mirror the public hospital protocol of their nearest tertiary centre, which is why a recommendation adopted at Royal North Shore can quickly spread across the North Shore private network.

Anticoagulation stewardship programs are quietly gaining traction. Drawing on experience from North American centres presented at Hospital Medicine 2017, several Australian hospitals now run daily weekday reviews of every newly started or continued NOAC, with a pharmacist, haematologist, or senior physician signing off on dose, indication, and duration. The early data — published in local QI registers and reviewed at meetings such as the Society of Hospital Medicine Australia symposium — suggest reductions in inappropriate dosing and shorter length of stay. The trick is sustainability: a program that depends on a single enthusiast collapses when that person takes long service leave, so formalising the process within the hospital's governance structure matters more than the original champion.

Practical steps at the bedside

A useful bedside routine takes about three minutes. Confirm the indication and the target CHA₂DS₂-VASc or VTE risk score. Calculate CrCl with Cockcroft-Gault using the admission weight, not the weight from three years ago. Check for interacting medications and over-the-counter supplements such as St John's wort. Decide the dose using the table above, and document the reason for any deviation from the standard dose. Set a review date — typically day three for inpatients, when renal function and clinical status have stabilised — and write the discharge plan in plain language for the GP.

For ongoing education, the top clinical updates from Hospital Medicine 2017 remain a useful summary of which evidence has matured enough for ward adoption. Pair those with the current NPS MedicineWise NOAC modules, and the average hospitalist will close most of the gap between abstract and bedside within a single audit cycle.

The single next step worth committing to today is this: the next time you prescribe a NOAC for an inpatient over 75, write the dose-reduction criteria in the progress notes alongside the prescription. Whether the team changes service overnight or the patient transfers to a rehabilitation facility, that one line of documentation travels with the medication chart and turns abstract evidence into a sustained clinical decision.