Clinical safety note: This page is for label-based checking and education. Confirm all doses, contraindications, procedure timing, and interaction issues before prescribing or dispensing.
Calculator form
Example data table
| Scenario | Key inputs | Expected label-based output | Main note |
|---|---|---|---|
| Adult NVAF, standard | Age 67, weight 82 kg, SCr 1.0 mg/dL | 5 mg twice daily | Fewer than two reduction criteria. |
| Adult NVAF, reduced | Age 84, weight 56 kg, SCr 1.3 mg/dL | 2.5 mg twice daily | Age and weight meet two criteria. |
| Adult DVT, day 3 | Therapy day 3 | 10 mg twice daily | Initial 7-day treatment phase. |
| Adult DVT, day 12 | Therapy day 12 | 5 mg twice daily | Maintenance treatment phase. |
| Pediatric VTE | Weight 20 kg, therapy day 9, initial anticoagulation completed | 3 mg twice daily | Falls in the 18 to <25 kg tier. |
Formula used
1) Adult NVAF dose-reduction rule
Use 5 mg twice daily for most adults. Reduce to 2.5 mg twice daily when at least two of these are present: age 80 years or older, body weight 60 kg or less, and serum creatinine 1.5 mg/dL or greater.
2) Adult DVT or PE phase logic
Treatment days 1 through 7 use 10 mg twice daily. Day 8 and beyond use 5 mg twice daily. After at least 6 months of treatment, extended recurrence reduction uses 2.5 mg twice daily.
3) Postoperative prophylaxis logic
Hip and knee replacement prophylaxis uses 2.5 mg twice daily. The first postoperative dose belongs in the 12 to 24 hour window. Hip surgery uses 35 days. Knee surgery uses 12 days.
4) Interaction adjustment rule
If a combined P-gp and strong CYP3A4 inhibitor is selected and the current regimen is 5 mg or 10 mg twice daily, the calculator halves the dose. If the regimen is already 2.5 mg twice daily, the calculator blocks numeric output and warns against coadministration.
5) Supportive kidney estimates
- Adult CrCl (Cockcroft-Gault): CrCl = ((140 − age) × weight in kg) ÷ (72 × serum creatinine). Multiply by 0.85 for females.
- Pediatric eGFR (updated Schwartz): eGFR = 0.413 × height in cm ÷ serum creatinine in mg/dL.
These renal estimates are displayed as support values. They are not the only prescribing decision points.
How to use this calculator
- Choose the correct indication first, because the dose logic changes by use case.
- Enter age, weight, and serum creatinine for atrial fibrillation checks.
- Enter therapy day for DVT, PE, and pediatric VTE phase selection.
- For postoperative prophylaxis, add hours since surgery to review the starting window.
- Screen for hepatic impairment, dialysis, strong inhibitors, and strong inducers.
- For pediatric cases, confirm at least 5 days of initial anticoagulation and enter height when renal screening matters.
- Press Calculate dose to place the result above the form and draw the Plotly dose graph.
- Use the CSV or PDF buttons to save the result summary for review.
FAQs
1) What does this calculator estimate?
It estimates label-based apixaban dosing pathways for adult NVAF, adult DVT or PE treatment, postoperative prophylaxis, extended recurrence reduction, and pediatric VTE weight-tier dosing.
2) When does adult NVAF dosing drop to 2.5 mg twice daily?
The lower adult NVAF dose appears when at least two criteria are present: age 80 years or older, weight 60 kg or less, and serum creatinine 1.5 mg/dL or greater.
3) Does kidney function always change the adult dose?
No. Adult dosing is indication-specific. The page shows supportive renal estimates, but the labeled adult dose rules do not use the same renal trigger across all indications.
4) How does the calculator handle DVT or PE treatment phases?
Enter therapy day. Days 1 through 7 map to the initial twice-daily starter dose. Day 8 and beyond map to the maintenance twice-daily dose.
5) Can this page calculate pediatric regimens?
Yes. It includes the weight-tier pediatric VTE table and checks whether at least 5 days of initial anticoagulation were completed before starting the oral regimen.
6) What interaction checks are included?
It screens for combined P-gp and strong CYP3A4 inhibitors, clarithromycin, and strong inducers. Unsupported or avoid scenarios trigger a hard-stop message instead of a silent numeric output.
7) Can this replace a prescription review?
No. It is a structured review aid. Final dosing still needs current prescribing information, a medication reconciliation, bleeding-risk assessment, and clinician judgment.
8) Why does the calculator sometimes refuse to show a number?
It blocks output when the label says dosing cannot be provided, a regimen is not recommended, an avoid interaction is selected, or a required safety check is missing.
Implementation notes
- Responsive calculator grid uses three columns on large screens, two on medium screens, and one on small screens.
- Result output appears below the header and above the form after submit.
- CSV and PDF buttons export the displayed result table.
- Plotly renders the phase-dose graph only when a numeric regimen is available.