Transdermal aspirin?

[Mike C]

Does anyone know if a transdermal aspirin patch exists yet? I´ve seen research studies showing the patch to be effective, yet I still don´t see them available on the market. I take one aspirin a day, but am worried about my gut and stomach bleeding. The patch would eliminate this risk.

[JGNI]

Does anyone know if a transdermal aspirin patch exists yet? I´ve seen research studies showing the patch to be effective, yet I still don´t see them available on the market. I take one aspirin a day, but am worried about my gut and stomach bleeding. The patch would eliminate this risk.

Wrong, the patch (which doesn't exist by the way) would not eliminate the risk of stomach bleeding. Even though it is true that regular aspirin can cause a direct irritation of the gastric mucosa if it dissolves there stuck on the gastric wall, it is not the reason most people can get gastric bleeding. This direct possible irritating effect of aspirin is easily overcome by using an enteric coated formula (will only dissolve once at at higher pH, meaning in your intestine). As with other NSAID drugs, aspirin inhibit formation of protective prostaglandins which are coating your stomach to protect it from its own acid production, resulting in possible irritation and bleeding. So no matter how you take it, it is a systemic effect that will always be there.
Bleeding elsewhere is non specific and would be related to the antiplatelet action of aspirin (what you are looking for when taking it).

If you are taking just a preventive dose of 80 mg a day because you are presenting risk factors (no reason otherwise) of cardiovascular disease and are otherwise healthy, risks of bleeding are low and benefits should outbalance these.

[JGNI]

I looked and found an article that demonstrates what I wrote before.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10519166&query_hl=2&itool=pubmed_docsum

[Mike C]

Transdermal modification of platelet function: an aspirin patch system results in marked suppression of platelet cyclooxygenase

B McAdam, RM Keimowitz, M Maher and DJ Fitzgerald
Centre for Cardiovascular Science, Royal College of Surgeons in Ireland, Dublin.
Aspirin inhibits platelet cyclooxygenase and prevents thromboxane A2 (TXA2) production. Although it is an effective antithrombotic, even at a low doses aspirin may induce gastrointestinal toxicity. We examined the feasibility of delivering aspirin transdermally using two patch systems, one without (type A) and one with (type B) the permeation enhancer limonene. Daily application of two type A patches that had a total surface area of 100 cm2 and contained 84 mg/patch resulted in 85% +/- 6% reduction in serum TXB2 in six male subjects by day 14. Suppression of serum TXB2 was less marked in females (32% +/- 16%). Analysis of the residual drug in the patch showed that each patch delivered 18 +/- 3 mg on day 1 and 17 +/- 4 mg on day 14, with no difference between males and females. Daily application of a single patch B that had a surface area of 50 cm2 and contained 120 mg aspirin resulted in 60% +/- 11% suppression of serum TXB2 by day 14 in nine male subjects and 84% +/- 9% suppression by day 21. Analysis of the applied patches showed that patch B delivered 33 +/- 3 mg of aspirin daily. Plasma aspirin and salicylate were determined by gas chromatography, mass spectrometry. No aspirin was detected, whereas plasma salicylate was 157 +/- 38 ng/ml and 133 +/- 20 ng/ml by day 14 with patch A and patch B, respectively. Analysis of aspirin applied by patch to the skin in three subjects showed marked hydrolysis to the inactive product, salicylic acid. Aspirin can be delivered transdermally by patch in a dose that suppresses platelet cyclooxygenase. The delivery rate is low reflecting hydrolysis of the drug in the skin. Delivery is improved by the permeation enhancer limonene. This novel route of delivery may be applicable to other antithrombotics and may limit the risk of gastrointestinal toxicity.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8627531&dopt=Abstract


Transdermal modification of platelet function. A dermal aspirin preparation selectively inhibits platelet cyclooxygenase and preserves prostacyclin biosynthesis

RM Keimowitz, G Pulvermacher, G Mayo and DJ Fitzgerald
Hematology Section, Gundersen Clinic, La Crosse, Wis.
BACKGROUND. Even low doses of oral aspirin inhibit prostacyclin (prostaglandin [PG] I2) formation and cause gastrointestinal toxicity. We examined the skin as a novel route for continuous low-dose aspirin administration and selective inhibition of platelet cyclooxygenase in humans. METHODS AND RESULTS. Aspirin 250 or 750 mg/d for 10 days induced a dose-dependent inhibition of serum thromboxane (TX) B2. At the highest dose, five of six subjects responded, with a mean reduction in serum TXB2 of 95 +/- 3% (P = .003). Urinary 2,3-dinor TXB2, an index of in vivo TXA2 formation, decreased by 68 +/- 7% and recovered slowly, consistent with inhibition of platelet cyclooxygenase in vivo. In contrast, PGI2 biosynthesis, determined as excretion of 2,3-dinor-6- keto PGF1 alpha, was 81 +/- 5% of baseline at 10 days. Intravenous bradykinin increased PGI2 biosynthesis 5.1 +/- 1.6-fold (n = 4) before aspirin treatment. Oral aspirin 75 mg/d for 14 days abolished bradykinin-induced PGI2 formation, whereas dermal aspirin 750 mg/d had no effect despite similar inhibition of TXA2 biosynthesis. In five subjects, plasma aspirin and salicylate were determined after a single application of 750 mg. Aspirin was absorbed slowly, with peak levels of 0.24 +/- 0.11 micrograms/mL at 3 hours. Salicylate levels peaked at 6 to 12 hours, with plasma levels of 0.79 +/- 0.14 micrograms/mL. CONCLUSIONS. Thus, it is possible to achieve selective inhibition of platelet cyclooxygenase by aspirin applied to the skin. This approach may be applicable to other antiplatelet agents and be useful in patients at risk for gastrointestinal bleeding or toxicity.

http://circ.ahajournals.org/cgi/content/abstract/88/2/556


These are some of the studies I was referring too. That´s interesting (and alarming) that even small amounts of aspirin in the blood can still cause stomach bleeding. I wonder if these results have been duplicated since 1999? How about taking aspirin with food? Any extra protection there? Man, I´ve been taking one 325mg tab per day for years. So far, I don´t notice any problems, but I think sooner or later I´m going to start bleeeding. My hemoglobin levels have been down for awhile, so I´m thinking this may be a result of the aspirin intake.

[JGNI]

Those studies are not showing that this mode of administration is preventing cardiovascular events neither that it is preventing or reducing gastrointestinal bleeding, interesting though. You would need a real long term study to show a real benefit. For now it is just exploration.

[SCI-Nurse]

Just because there is research available on it, it doesn't mean it is available to the general public.
And the research is necessary to see if there is a need, is helpful, or any complications before FDA approval and of course, to work out the kinks if possible.
I think patches (for everything?) is the future! CWO