Vioxx and Heart Attack Risk
Vioxx (rofecoxib), a COX-2 inhibitor pain reliever, carried a significantly elevated risk of heart attack (myocardial infarction) and stroke compared to placebo or other NSAIDs. Clinical trials and post-marketing data showed this risk increased with higher doses and longer use, leading to its voluntary withdrawal from the market in 2004 by Merck.[1]
Key Evidence from APPROVe Trial
The pivotal APPROVe trial (2000-2004) tested Vioxx 25 mg daily for polyp prevention in 2,586 patients. After 18 months, it found:
- 0.74% annual risk of cardiovascular events (heart attack, stroke, or sudden cardiac death) on Vioxx vs. 0.50% on placebo—a 46% relative increase (hazard ratio 1.92, 95% CI 1.20-3.07).
- Absolute risk difference: about 0.24% per year, or roughly 1 extra event per 385 patients treated for a year.
Risk rose sharply after 18 months (hazard ratio 3.14).[2][3]
Dose and Duration Effects
Lower doses (12.5-25 mg) showed smaller risks in earlier trials like VIGOR (vs. naproxen), but still doubled cardiovascular events (relative risk 2.38).[4] Risk scaled with exposure:
- Short-term (<3 months): Minimal elevation.
- Long-term (>18 months): Up to 3-fold increase.
Meta-analyses confirmed consistent dose-response across studies.[5]
Comparison to Other Pain Relievers
| Drug/Treatment | Relative CV Risk vs. Placebo (from meta-analyses) |
|----------------|--------------------------------------------------|
| Vioxx 25 mg | 1.9-2.3x |
| Celebrex 400 mg | 1.2-1.6x (dose-dependent) |
| Naproxen | Neutral (1.0x) |
| Ibuprofen | 1.1x |
Vioxx's risk exceeded non-selective NSAIDs like naproxen, which may protect the heart via anti-platelet effects.[6]
Why the Risk Occurred
Vioxx selectively blocked COX-2 (inflammation enzyme) but spared COX-1 less than expected, reducing prostacyclin (vasodilator) without fully inhibiting thromboxane (pro-clotting). This imbalance promoted thrombosis, especially in patients with heart disease risk factors.[7]
Who Was Most at Risk?
- Age >65.
- Prior heart disease, hypertension, or diabetes.
- Smokers or those on statins.
- Long-term, high-dose users.
FDA later warned similar risks for all COX-2 inhibitors.[8]
What Happened After Withdrawal
Merck pulled Vioxx amid lawsuits claiming hidden risks; over 27,000 suits settled for $4.85 billion. No generic Vioxx exists today. Patients switched to lower-risk options like naproxen or acetaminophen.[9]
[1]: FDA Vioxx Label (archived). Link
[2]: NEJM: APPROVe Results (2005). Link
[3]: Lancet Meta-Analysis (2004). Link
[4]: NEJM: VIGOR Trial (2000). Link
[5]: JAMA Meta-Analysis (2006). Link
[6]: Circulation Review (2005). Link
[7]: Nature Reviews Drug Discovery (2005). Link
[8]: FDA COX-2 Warning (2005). Link
[9]: Merck Settlement (2007). Link