Effect of non-selective, non-steroidal anti-inflammatory drugs and cyclo-oxygenase-2 selective inhibitors on the PFA-100 closure time

Effectiveness of Platelet Function Analyzer-100 for Laboratory Detection of Anti-Platelet Drug-Induced Platelet Dysfunction

BACKGROUND

High on-treatment platelet reactivity (HTPR) is the phenomenon wherein patients exhibit normal platelet activity in laboratory testing despite adequate adherence to anti-platelet treatment. We investigated the detection rates of Platelet Function Analyzer (PFA)-100 (Dade Behring AG, Düdingen, Switzerland) for drug-induced platelet dysfunction and analyzed potential contributors to HTPR with practical PFA-100 data over six years.

METHODS

We used data from 6,957 patients who underwent PFA-100 testing after receiving aspirin, clopidogrel, or non-steroidal anti-inflammatory drugs (NSAIDs). Of these, 6,163 patients were tested with only the collagen/epinephrine cartridge (Col/EPI) of PFA-100; 794 were tested with both Col/EPI and the collagen/ADP cartridge (Col/ADP). We calculated PFA-100 closure time (CT) for each drug and compared the clinical and laboratory characteristics of the patients with prolonged CTs and normal CTs (i.e., HTPR).

RESULTS

In Col/EPI, 73.2% (365/499), 72.6% (390/537), and 55.3% (3,442/6,228) patients showed prolonged CTs for aspirin, clopidogrel, and NSAIDs, respectively. In Col/ADP, prolonged CTs were observed in 37.4% (34/91), 43.2% (35/81), and 29.6% (200/676) of patients receiving aspirin, clopidogrel, and NSAIDs, respectively. Of the patients tested with both cartridges, 88.9% (48/54), 95.3% (41/43), and 89.0% (577/648) of the patients receiving aspirin, clopidogrel, and NSAIDs had prolonged CTs, and 10.0% (79/794) showed normal CTs regardless of drugs. For clopidogrel users (both cartridges), there were more patients with malignancies in the normal CT than prolonged CT group.

CONCLUSIONS

PFA-100 is not sufficiently effective for laboratory screening of drug-induced platelet dysfunction. Malignancy may contribute to clopidogrel-related HTPR in PFA-100.

Meloxicam and diclofenac do not change VEGF and PDGF-ABserum levels of platelet-rich plasma

BACKGROUND/AIM

Platelet-rich plasma (PRP) application has gained widespread interest for musculoskeletal injuries. Nonsteroidal antiinflammatory drugs are frequently used in sports medicine before and/or after PRP application. Our study seeks to determine whether serum levels of platelet-derived growth factor-AB (PDGF-AB) and vascular endothelial growth factor (VEGF) levels of PRP would be affected by nonsteroidal antiinflammatory drugs.

MATERIALS AND METHODS

Two different final concentrations of diclofenac (0.5 μg mL^-1 and 2.5 μg mL^-1), meloxicam (0.8 μg mL^-1 and 2.0 μg mL^-1), and acetylsalicylic acid (final concentration 450 μm) were obtained in separate tubes with PRPs prepared from 20 healthy male volunteers. Medicine-free PRP was the control group. Growth factors were measured using ELISA.

RESULTS

PDGF-AB and VEGF serum levels did not change with diclofenac, meloxicam, or acetylsalicylic acid addition. PDGF-AB and VEGF serum levels correlated with each other.

CONCLUSION

Diclofenac, meloxicam, and acetylsalicylic acid did not affect PDGF-AB and VEGF serum levels.

Effects of Firocoxib, Flunixin Meglumine, and Phenylbutazone on Platelet Function and Thromboxane Synthesis in Healthy Horses

OBJECTIVE

Determine the effects of nonsteroidal anti-inflammatory drugs (NSAID) on platelet function and thromboxane synthesis immediately after drug administration and following 5 days of NSAID administration in healthy horses.

STUDY DESIGN

Randomized cross-over study.

ANIMALS

Healthy adult horses (n=9; 6 geldings and 3 mares).

METHODS

Horses received either flunixin meglumine (1.1 mg/kg IV every 12 hours), phenylbutazone (2.2 mg/kg IV every 12 hours), or firocoxib (loading dose of 0.27 mg/kg IV on day 1, then 0.09 mg/kg IV every 24 hours for 4 days) for a total of 5 days. Blood samples were collected prior to drug administration (day 0), 1 hour after initial NSAID administration (day 1), and then 1 hour post-NSAID administration on day 5. Platelet function was assessed using turbidimetric aggregometry and a platelet function analyzer. Serum thromboxane B₂ concentrations were determined by commercial ELISA kit. A minimum 14 day washout period occurred between trials.

RESULTS

At 1 hour and 5 days postadministration of firocoxib, flunixin meglumine, or phenylbutazone, there was no significant effect on platelet aggregation or function using turbidimetric aggregometry or a platelet function analyzer. There was, however, a significant decrease in thromboxane synthesis at 1 hour and 5 days postadministration of flunixin meglumine and phenylbutazone that was not seen with firocoxib.

CONCLUSION

Preoperative administration of flunixin meglumine, phenylbutazone, or firocoxib should not inhibit platelet function based on our model. The clinical implications of decreased thromboxane B₂ synthesis following flunixin meglumine and phenylbutazone administration are undetermined.

COX-2 inhibition: what we learned--a controversial update on safety data

IMPORTANCE

Cyclooxygenase type 2 (COX-2)-selective nonsteroidal anti-inflammatory drugs (NSAIDs) (c2sNSAIDs) have been scrutinized relative to the less costly nonselective NSAIDs (nsNSAIDs). The conclusions reached were not always consistent with the data, and best treatment choices for patients were not always recommended.

OBJECTIVE

The data that were used to criticize the c2sNSAIDs are reexamined in a controversial light, demonstrating that the presence of reverse bias was often, but not always, present.

EVIDENCE REVIEW

A review of both Pubmed and news media articles relating to nsNSAIDs and c2sNSAIDs was conducted. References were selected on the basis of relevance to the controversies.

FINDINGS

The initial claims for the c2sNSAIDs of reduced gastrointestinal (GI) injury and preservation of platelet function were soon dwarfed by concerns regarding increased cardiovascular (CV) risk with publication of the Vioxx Gastrointestinal Outcomes Research trial for rofecoxib. Initial prothrombotic theories had a poor basis for explaining these concerns and have since largely been replaced with more credible explanations, including blood pressure elevations known to occur with all NSAIDs. Between data suggesting increased CV risk and under political pressure and public outcry, rofecoxib was withdrawn from the market in 2004. Soon, all c2sNSAIDs were under scrutiny. The Food and Drug Administration has since grouped all NSAIDs, whether c2sNSAID or nsNSAID, into one class with similar warnings regarding skin, CV, renal, and GI side effects.

CONCLUSIONS AND RELEVANCE

The entire "COX-2 debacle" is reminiscent of past events with NSAIDs. Amid this public, media, and political hysteria, it is not clear if we will see any more NSAIDs (selective or otherwise) approved in the near future.

Parecoxib and indomethacin delay early fracture healing: a study in rats

Nonsteroidal antiinflammatory drugs (NSAIDs) are used to reduce inflammatory response and pain. These drugs have been reported to impair bone metabolism. Parecoxib, a specific COX-2 inhibitor, exerts an inhibitory effect on the mineralization of fracture callus after a tibial fracture in rats. Decreased bone mineral density (BMD) at a fracture site may indicate impairment of early healing, casting doubt on the safety of using COX-2 inhibitors during the early treatment of diaphyseal fractures. Forty-two female Wistar rats were randomly allocated to three groups. They were given parecoxib, indomethacin, or saline intraperitoneally for 7 days after being subjected to a closed tibial fracture stabilized with an intramedullary nail. Two and 3 weeks after surgery, the bone density at the fracture site was measured using dual energy xray absorptiometry (DEXA). Three weeks after the operation the rats were euthanized and the healing fractures were mechanically tested in three-point cantilever bending. Parecoxib decreased BMD at the fracture site for 3 weeks after fracture, indomethacin for 2 weeks. Both parecoxib and indomethacin reduced the ultimate bending moment and the bending stiffness of the healing fractures after 3 weeks. These results suggest COX inhibitors should be avoided in the early phase after fractures.

Point-of-care assessment of antiplatelet agents in the perioperative period: a review

The aim of this paper was to review the strengths and limitations of current 'point-of-care' techniques for the detection of antiplatelet drug effects. The review was based on a Medline search for articles with key words related to "platelet function tests", "point-of-care", and "anaesthesia", published in English between January 1996 and September 2008. It was found that global assessments of 'haemostasis', such as the standard thrombelastograph, Sonoclot, Clot Signature Analyser and Hemodyne, are not specific for platelet function and are essentially insensitive to cyclooxygenase inhibitors (aspirin, non-steroidal anti-inflammatory drugs) and P2Y12 antagonists (ticlopidine, clopidogrel). Global assessments of 'platelet function', such as the PFA-100 and PlateletWorks, are more specific for platelet function, but also have limited sensitivity for cyclooxygenase inhibitors and P2Y12 antagonists. The newer devices developed specifically for the assessment of antiplatelet drugs, such as Platelet Mapping, the Impact Cone and Platelet Analyser and the VerifyNow, are more promising, but are not as sensitive as laboratory platelet aggregometry. All three categories of devices detect G(p)II(b)/III(a) antagonists (abciximab, tirofiban, eptifibatide) activity, but not all provide quantitative assessments for monitoring therapy. The limitations appeared to be related to the complexity of platelet function, the multiple pathways of platelet activation, the wide interpatient variability in platelet responses and the interdependence between platelets and other aspects of coagulation. The strengths and limitations of point-of-care devices should be appreciated before they are used to assist clinical decision-making in the perioperative period.

The effects of nonsteroidal anti-inflammatory drugs on platelet function and severity of upper gastrointestinal haemorrhage

Nonsteroidal anti-inflammatory drugs (NSAIDs) cause gastrointestinal (GI) damage primarily due to the inhibition of prostaglandin synthesis in gastric mucosa, which is an important factor in mucosa protection. Platelets are a cardinal feature of vascular repair. A variety of angiogenic stimulators are stored in platelets and are released during clotting at the wound. When there is a defect in any of these functions and/or platelet number, haemostasis is usually impaired and there may be an associated increased risk and severity of bleeding. While the mechanism of mucosal injury and bleeding are well documented with the use of NSAIDs, very little is known about the platelet function abnormalities and their effects on severity of upper GI bleedings. We performed a prospective analysis of 49 patients who had a history of NSAIDs use to investigate the association between the platelet function impairment associated with NSAIDs and severity of upper GI haemorrhages. Thirty-six of 49 patients (73.5%) had deteriorated platelet function. Mean severity score of patients with deteriorated platelet functions was 3.39, and that of patients with normal platelet functions was 2.46. Mean severity score was statistically significantly higher in patients with deteriorated platelet functions. In conclusion, impaired platelet functions associated with NSAIDs may cause more severe upper GI bleeding. Clinicians should be alert for GI complications especially in older patients and in those with a history of ulcer bleeding.

Comprehensive preoperative evaluation of platelet function in total knee arthroplasty patients taking diclofenac

The severity and variability of platelet dysfunction in preoperative arthritic patients taking nonsteroidal anti-inflammatory drugs (NSAIDs) have not been well studied previously. We evaluate 30 preoperative patients taking diclofenac (group D) by routine coagulation screen, platelet count, fibrinogen concentration, thrombelastography, and PFA-100 (Dade Behring, Inc, Deerfield, IL)) platelet function analyzer. Ten patients (group P) and 30 healthy volunteers (group N) not taking NSAIDs serve as control. Diclofenac causes significant prolongation of mean PFA-100 closure times (P < .0001). However, the prolongation is highly variable; and up to 33% of patients are still having normal platelet function despite diclofenac consumption. Low body weight is a significant predictor of more severe platelet dysfunction (P < .01). Other tests are not useful. We conclude that not all patients taking NSAIDs have similar platelet dysfunction and that preoperative monitoring with PFA-100 is preferable.

Patients with rheumatoid arthritis undergoing surgery: how should we deal with antirheumatic treatment?

OBJECTIVES

To review published data on the perioperative management of antirheumatic treatment and perioperative outcome in patients with rheumatoid arthritis (RA).

METHODS

The review is based on a MEDLINE (PubMed) search of the English-language literature from 1965 to 2005, using the index keywords "rheumatoid arthritis" and "surgery". As co-indexing terms the different disease-modifying antirheumatic drugs (DMARDs) as well as nonsteroidal anti-inflammatory drugs (NSAIDs) and "glucocorticoids" were used. In addition, citations from retrieved articles were scanned for additional references. Furthermore, because the number of published articles is so limited, relevant abstracts presented at congresses were included in the analysis.

RESULTS

Continuation of methotrexate (MTX) appears to be safe in the perioperative period. Only a limited number of studies address the use of leflunomide and the results are conflicting. Because of the very long drug half-life, its discontinuation would need to be of long duration and is probably not necessary. Data on hydroxychloroquine do not show increased risks of infection. Regarding sulfasalazine, there are no studies from which definite answers could be drawn on whether it should be withheld perioperatively. Preliminary data show that the risk of infections during treatment with TNF-blocking agents may be lower than initially expected. The only available recommendation (Club Rhumatismes et Inflammation, CRI) suggests discontinuing the drugs before surgery for several weeks, depending on the risk of infection and the drug used. They should not be restarted until wound healing is complete. To avoid the antiplatelet effect during surgery, NSAIDs other than aspirin should be withheld for a duration of 4 to 5 times the drug half-life. Patients with chronic glucocorticoid therapy and suppressed hypothalamic-pituitary-adrenal (HPA) axis need perioperative supplementation.

CONCLUSIONS

While continuation of MTX likely is safe, data on other DMARDs are sparse. In particular, more data on the perioperative use of the biologic agents are needed.

Paradoxical rebound platelet activation after painkillers cessation: missing risk for vascular events?

BACKGROUND

Several reliable reports strongly indicate that the use of nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors is associated with an increased risk of cardiovascular events. Considering the key role of platelets in coronary atherosclerosis and the fact that antiplatelet therapy with aspirin (and more recently, clopidogrel) has been associated with reduced vascular mortality, we sought to determine the effect of therapy and withdrawal of NSAIDs and COX-2 inhibitors on platelet activity.

METHODS

Platelet characteristics from 34 aspirin-naive volunteers who were receiving NSAIDs and COX-2 inhibitors were compared with 138 drug-free controls. Platelets were assessed twice at baseline (at least 1 month of NSAIDs and COX-2 inhibitors) and after a 14-day washout. We used adenosine diphosphate-induced conventional aggregometry, the point-of-care Ultegra analyzer (Ultegra Accumetrics, San Diego, Calif), and whole blood flow cytometry.

RESULTS

Platelet activity during therapy with NSAIDs and COX-2 inhibitors was similar and unremarkable between groups. However, there was a highly significant increase of platelet activity as assessed by conventional aggregometry (P=.0003), Ultegra analyzer readings (P=.03), and expression of GPIIb/IIIa (P=.02), P-selectin (P=.03), and platelet endothelial cell adhesion molecule-1 (P=.001) after withdrawal from NSAIDs and COX-2 inhibitors.

CONCLUSIONS

These data suggest that drug cessation, rather than continuous therapy with NSAIDs and COX-2 inhibitors, may be associated with rebound platelet activation, which may predispose one to a higher risk of vascular events. This hypothesis requires intensive testing in crossover randomized studies and may justify more aggressive antiplatelet regimens in patients after discontinuation of therapy with NSAIDs and COX-2 inhibitors.