01Purpose and principlesWhat the treatment does and how it fits into care.
Anticoagulants alter clotting-factor activity. Their benefit depends on the untreated event being sufficiently likely and sufficiently serious to justify the bleeding risk introduced by treatment. The same person can have a strong indication for anticoagulation and several modifiable bleeding risks. Recurrent falls, uncontrolled blood pressure, an interacting analgesic or excess alcohol should prompt a plan to reduce harm; they are not interchangeable with a demonstrated absolute contraindication. Shared decisions should distinguish an annual preventive benefit from the immediate need to treat an established clot. Record what the patient values, because daily treatment burden, monitoring access and concern about either stroke or bleeding influence whether the agreed regimen will actually be taken.
Direct oral anticoagulants inhibit either factor Xa or thrombin and are prescribed as fixed regimens within specific indication and patient criteria. Fixed does not mean universally interchangeable. A reduced atrial-fibrillation dose cannot be transferred to acute venous thrombosis simply because the person is old. Vitamin K antagonists remain important for circumstances such as mechanical heart valves; their effect is titrated using INR and they have different transition and monitoring requirements. Injectable anticoagulants remain useful in selected settings, including pregnancy and some inpatient pathways. The safe clinical question is therefore not which drug is strongest, but which licensed and guideline-supported strategy fits this indication, physiology and follow-up system.
Key points
- Write the indication and treatment phase before selecting a dose: atrial-fibrillation prevention, acute venous thrombosis treatment and extended recurrence prevention use different schedules.
- For non-valvular atrial fibrillation, apixaban is usually 5 mg orally twice daily long term; use 2.5 mg twice daily when at least two of age 80 years or over, weight 60 kg or less and serum creatinine 133 micromol/L or over apply.
- Apixaban for acute DVT or PE is 10 mg orally twice daily for 7 days, then 5 mg twice daily; assess treatment duration at 3 months. The 2.5 mg twice-daily recurrence-prevention regimen follows at least 6 months of treatment.
- Calculate creatinine clearance for DOAC dosing and confirm the individual product rules. For apixaban in atrial fibrillation, clearance 15–29 mL/min requires 2.5 mg twice daily; below 15 mL/min or dialysis, this UK product is not recommended.
- Obtain full blood count, kidney and liver tests, body weight, interacting medicines and a bleeding history before prescribing; arrange a named review and repeat testing during intercurrent illness.
- A DOAC does not require routine INR titration. A normal conventional clotting result cannot reliably establish that clinically important drug activity is absent.
- Explain missed-dose instructions, bleeding action, alert-card use and how planned procedures are coordinated. Never create an unplanned treatment gap when changing anticoagulants.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
Identify documented atrial fibrillation, the date and site of venous thrombosis, a mechanical valve, or another specialist indication. In atrial fibrillation, use the current NICE stroke-risk and bleeding-risk approach, including CHA2DS2-VASc and ORBIT, while addressing modifiable hazards. Antiplatelet treatment is not a substitute for indicated stroke-prevention anticoagulation. A historical entry saying blood thinner is inadequate evidence of the original indication.
Ask what was swallowed and when, rather than relying only on the electronic prescription. Twice-daily drugs require a realistic routine. Check hospital discharge changes, community supplies, monitored dosage systems and medicines bought without a prescription. A missing morning dose and a deliberate perioperative interruption have different implications. Reconcile the last dose before deciding whether an additional anticoagulant is due.
Explore previous gastrointestinal or intracranial bleeding, anaemia, thrombocytopenia, hepatic disease, uncontrolled hypertension and recent injury. Ask about aspirin, clopidogrel, NSAIDs and herbal products as well as prescribed interacting drugs. A falling haemoglobin without obvious bleeding merits investigation. Avoid reducing a licensed dose without criteria as a substitute for identifying and correcting a remediable source of bleeding.
Pregnancy, breastfeeding, very low or high body weight, rapidly changing kidney function and significant liver disease require a medicine-specific strategy. DOACs should not be assumed suitable in pregnancy or for mechanical valves. In advanced frailty, ask whether treatment can be administered reliably and whether the balance has changed; chronological age alone does not answer either question.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Full blood count and haemoglobin trendFirst step - Why
- Establish baseline blood counts and detect occult blood loss.
- Interpretation and limitations
- A single haemoglobin value must be compared with previous results and the clinical picture. Thrombocytopenia can alter treatment suitability, while unexplained anaemia may represent ongoing bleeding. An expected postoperative fall is not a reason to ignore continuing deterioration. Record who will investigate an abnormal result before issuing repeated supplies.
- 02
Creatinine clearance using appropriate inputs - Why
- Determine the renal category required by the chosen anticoagulant.
- Interpretation and limitations
- Use a current creatinine, age and measured weight with an appropriate Cockcroft–Gault calculation for DOAC dosing. eGFR reported by the laboratory may place a small older person in a different category. Neither estimate is dependable during rapidly evolving acute kidney injury; trend, urine output and acute assessment become essential.
- 03
Liver tests and clinical hepatic assessment - Why
- Identify liver disease that changes bleeding and medicine handling.
- Interpretation and limitations
- Transaminase elevation alone is not a complete assessment of hepatic synthetic function. Review bilirubin, albumin, clotting context, decompensation and the product restrictions. Apixaban is contraindicated where liver disease causes coagulopathy with clinically relevant bleeding risk. Do not infer that a normal creatinine neutralises the risks of decompensated cirrhosis.
- 04
Targeted assessment during acute bleeding - Why
- Define the site, severity and timing of anticoagulant exposure.
- Interpretation and limitations
- Send emergency blood tests and cross-match as clinically indicated, document the exact last dose and seek the relevant reversal pathway. Drug-specific assays may help when available, but resuscitation and specialist discussion must not wait for an assay that cannot return promptly. Interpret routine coagulation tests according to the agent rather than as a universal exclusion test.
04Treatment approachPreparation, options, escalation and aftercare.
01InitiationChoose an atrial-fibrillation regimenFirst stepA stable adult has an agreed indication for stroke-prevention anticoagulation.+
- 1Confirm the rhythm diagnosis and risk assessment, discuss expected benefit and bleeding concerns, then exclude circumstances needing a different strategy, including a mechanical valve or pregnancy. Agree who will prescribe and monitor after initiation.
- 2Check weight, full blood count, liver function and creatinine clearance. Apply the product-specific criteria to the selected agent and indication; do not combine thresholds remembered from several different DOACs into an invented dose rule.
- 3Prescribe the medicine with route, dose and frequency, document why any reduced dose is appropriate, and provide patient-specific instructions about missed doses and bleeding. Ask the person to describe how the regimen will fit their day.
- 4Book an early review of adherence, adverse effects and practical access, followed by ongoing laboratory and clinical review. Arrange earlier reassessment when illness, dehydration, weight change or a newly prescribed interaction could alter exposure.
02Acute treatmentCarry a venous-thrombosis schedule across dischargeAn adult is starting oral treatment after confirmed DVT or pulmonary embolism.+
- 1Confirm that immediate oral treatment is suitable and check haemodynamic stability, kidney function, bleeding risk, cancer context and other reasons a different pathway might be required. Record the actual first treatment dose and date.
- 2For apixaban, prescribe the initial 10 mg twice-daily oral phase for exactly 7 days and identify the calendar date on which 5 mg twice daily begins. Provide enough correctly labelled tablets and remove any contradictory prescription.
- 3Explain that a lower tablet strength does not itself define the correct treatment phase. Check the discharge summary, pharmacy label and patient account all agree, particularly when the initial course began several days before discharge.
- 4Plan review after 3 months to assess provoking factors, recurrence risk, bleeding and preferences. If extended prevention is chosen after at least 6 months, make the change to the appropriate recurrence-prevention regimen explicit rather than allowing an old acute prescription to persist.
03DeteriorationRespond to a suspected major bleedAn anticoagulated adult presents with significant bleeding or haemodynamic compromise.+
- 1Start emergency assessment and resuscitation, withhold further anticoagulant doses and obtain senior help. Establish the bleeding site and call the relevant emergency specialty; physiological instability outweighs apparently reassuring initial laboratory numbers.
- 2Identify the exact agent, dose, last administration, indication and kidney function. Check antiplatelets and interacting medicines, because reversal decisions depend on the likely residual exposure and the clinical severity rather than simply on a positive medication history.
- 3Use the local major-haemorrhage and agent-specific reversal pathway with haematology or other appropriate expertise. Reversal, transfusion, endoscopy, intervention or surgery address different components of harm and may need to proceed together.
- 4After control, document a deliberate reassessment of whether and when anticoagulation should restart. Leaving a previously strong thrombotic indication untreated indefinitely through omission can create a second preventable event.
05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.
Apixaban for non-valvular atrial fibrillation
5 mg orally twice daily long term; reduce to 2.5 mg twice daily for at least two of age ≥80 years, weight ≤60 kg and serum creatinine ≥133 micromol/L, or for CrCl 15–29 mL/min.UK SmPC regimen, distinct from VTE dosing. Not recommended with CrCl below 15 mL/min or dialysis; avoid hepatic coagulopathy, assess major interactions and pregnancy, and reassess during acute illness.
Apixaban for DVT or pulmonary embolism
10 mg orally twice daily for 7 days, then 5 mg twice daily; review duration at 3 months. For continuing recurrence prevention after at least 6 months, 2.5 mg orally twice daily.National duration review and product dose schedule answer different questions. Use caution with CrCl 15–29 mL/min; not recommended below 15 mL/min. Do not import AF age/weight dose-reduction criteria into acute VTE treatment.
06Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- Review an unexplained change in bruising, fatigue, dark stools, haematuria or breathlessness promptly. Monitoring is a clinical process as well as a scheduled blood test, and a patient may identify bleeding before a routine appointment occurs.
- Check full blood count, liver function and renal function at least annually once stable, with more frequent review for older or frail people, impaired clearance or intercurrent illness. Select the interval using current SPS guidance and the individual trajectory.
- At every transition, reconcile the indication, exact agent, last dose, intended duration and next review. A specialist decision to combine antiplatelets and anticoagulation needs its own stop or reassessment date and clearly assigned ownership.
- Confirm that procedures, dental work and new prescriptions trigger an anticoagulant check. Interruption and restart timing depend on procedural bleeding risk, renal handling and thrombotic risk; the patient should receive a specific coordinated plan.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Dose criteria are logical rules
An 80-year-old weighing 59 kg meets two apixaban AF reduction criteria even with creatinine below 133 micromol/L. Conversely, age alone does not satisfy the two-criterion rule. Write each input separately so that a correct result is reproducible.
A drug level has a question
The useful question during urgent surgery may be whether substantial anticoagulant activity remains. During routine follow-up the useful questions are usually adherence, bleeding, kidney function and interactions. Ordering an INR does not convert a DOAC into a titratable warfarin-like treatment.
Bleeding scores support action
A bleeding estimate is most useful when it changes modifiable risks, follow-up intensity or the discussion of trade-offs. It is not a replacement for evaluating an active bleed or a reason to ignore a major indication for stroke prevention.
Transitions deserve calendar dates
A discharge instruction saying reduce after one week is ambiguous when treatment started in hospital. Writing the actual change date helps the patient, pharmacist and community prescriber reach the same answer without reconstructing the admission.
08Common pitfallsFrequent interpretation and management errors.
- 01
Prescribing a reduced DOAC dose solely because a patient appears frail can sacrifice effectiveness while leaving the actual source of bleeding risk untreated.
- 02
Continuing hospital heparin alongside a newly started DOAC without a deliberate switching plan can create unintended duplicate anticoagulation.
- 03
Using a normal INR to exclude relevant apixaban exposure can falsely reassure a team preparing urgent surgery or investigating bleeding.
- 04
Allowing temporary interruption to become an undocumented permanent stop leaves the original stroke or recurrence risk unaddressed.