Question

Could you use saturated sodium bicarbonate as a test reagent to distinguish between the following pairs of compounds

1. Aspirin and ibuprofen

2. Aspirin and methyl salicylate

Explain you rationale clearly, describing what you might expect to observe when each substance is mixed with the test reagent

Answer 1

If your doctor told you to take aspirin to help prevent a heart attack, you need to know that taking ibuprofen at the same time, for pain relief, may interfere with the benefits of aspirin for the heart. It is all right to use them together, but the FDA recommends that you contact your doctor for more information on the timing of when to take these two medicines, so that both medicines can be effective.

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.