Comparison of oral aspirin versus topical applied methyl salicylate for platelet inhibition.
BACKGROUND
Oral acetylsalicylic acid (aspirin) is the primary antiplatelet therapy in the treatment of acute myocardial infarction and acute coronary syndrome. Methyl salicylate (MS; oil of wintergreen) is compounded into many over-the-counter antiinflammatory muscle preparations and has been shown to inhibit platelet aggregation locally and to be absorbed systemically.


OBJECTIVE
To assess the ability of topically applied MS to inhibit systemic platelet aggregation for patients who are unable to tolerate oral drug therapy.


METHODS
A randomized, prospective, blinded, crossover study was conducted in 9 healthy men, aged 30-46 years. All subjects ingested 162 mg of aspirin or applied 5 g of 30% MS preparation to their anterior thighs. There was a minimum 2-week washout period between study arms. Blood and urine were collected at baseline and at 6 hours. An aggregometer measured platelet aggregation over time against 5 standard concentrations of epinephrine, and a mean area under the curve (AUC) was calculated. Urinary metabolites of thromboxane B(2) were measured by a standard enzyme immunoassay. Differences in and between groups at baseline and 6 hours were tested by the Wilcoxon signed-rank test.


RESULTS
Baseline platelet aggregation did not differ significantly between the 2 arms of the study (median AUC [% aggregation(*)min]; binominal confidence intervals): aspirin 183; 139 to 292 versus MS 197; 118 to 445 (p = 0.51). Both aspirin and MS produced statistically significant platelet inhibition; aspirin decreased the AUC from 183; 139 to 292 to 85; 48 to 128 (p = 0.008) and MS decreased the AUC from 197; 118 to 445 to 112; 88 to 306 (p = 0.011). No significant difference was detected between baseline and 6-hour thromboxane levels for either aspirin (p = 0.779) or MS (p = 0.327).


CONCLUSIONS
Topical MS and oral aspirin both significantly decrease platelet aggregation in healthy human volunteers.
Tanen
David A
DA
Department of Emergency Medicine, Naval Medical Center San Diego, San Diego, CA 92134, USA. david.tanen@med.navy.mil
Danish
D Christopher
DC
Reardon
Jacqueline M
JM
Chisholm
Christopher B
CB
Matteucci
Michael J
MJ
Riffenburgh
Robert H
RH
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000328:Adult; D019540:Area Under Curve; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004837:Epinephrine / Q000008:administration & dosage; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D011446:Prospective Studies; D012459:Salicylates / Q000008:administration & dosage / Q000494:pharmacology*; D018709:Statistics, Nonparametric; D013929:Thromboxane B2 / Q000652:urine; D013997:Time Factors
D010975:Platelet Aggregation Inhibitors; D012459:Salicylates; D013929:Thromboxane B2; C033069:methyl salicylate; D001241:Aspirin; D004837:Epinephrine