Floaters After Starting Effient (Prasugrel)
Floaters are not a recognized adverse effect of prasugrel (Effient) based on available clinical trial data and guidelines, and this symptom should prompt evaluation for unrelated ophthalmologic causes rather than being attributed to the medication.
Evidence from Clinical Trials
The major clinical trials evaluating prasugrel, including TRITON-TIMI 38, did not identify floaters or other visual disturbances as adverse effects of the medication 1. The primary safety concerns with prasugrel consistently center on bleeding complications, including:
- Major bleeding (2.4% vs 1.8% with clopidogrel) 1
- Life-threatening bleeding (1.4% vs 0.9% with clopidogrel) 1
- Fatal bleeding (0.4% vs 0.1% with clopidogrel) 1
- CABG-related bleeding (13.4% vs 3.2% with clopidogrel) 1
Mechanism Considerations
Prasugrel is a thienopyridine that irreversibly inhibits platelet aggregation through P2Y12 receptor blockade 1. While the increased bleeding risk could theoretically cause:
- Vitreous hemorrhage - which would be visible on slit-lamp examination and associated with more severe symptoms than simple floaters 2
- Retinal hemorrhage - which would be detected on fundoscopic examination 2
Simple floaters without hemorrhage have no plausible mechanistic connection to prasugrel's antiplatelet effects.
Alternative Causes to Evaluate
When a patient on prasugrel reports new floaters, consider these common ophthalmologic causes:
- Posterior vitreous detachment (PVD) - the most common cause of acute floaters, occurring in 14% of patients presenting with floaters/flashes 2
- Retinal tear - present in 14% of patients with acute PVD, with risk increasing to 5.0 times if visual reduction is present 2
- Age-related vitreous changes - benign vitreous syneresis 3, 4
Critical Red Flags Requiring Urgent Ophthalmology Referral
The following features suggest retinal tear or detachment rather than medication effect:
- Subjective visual reduction (likelihood ratio 5.0 for retinal tear) 2
- Vitreous hemorrhage on examination (likelihood ratio 10 for retinal tear) 2
- New onset of ≥10 floaters (likelihood ratio 8.1-36 for retinal tear) 2
- Flashes accompanying floaters 3, 2, 5
Clinical Approach
All patients presenting with new floaters should undergo:
- Visual acuity testing in each eye 2
- Ophthalmoscopic examination to assess for vitreous hemorrhage, retinal tears, or detachment 3, 2
- Urgent ophthalmology referral if any high-risk features are present 3, 2
Do not attribute floaters to prasugrel - this delays appropriate ophthalmologic evaluation for potentially sight-threatening conditions 3, 2.
Timing Considerations
If floaters developed within 6 weeks of starting prasugrel and the patient has known PVD, there is a 3.4% baseline risk of developing a retinal tear during this period unrelated to medication 2. The temporal association with prasugrel initiation is likely coincidental rather than causal.