In 2003 the Spanish researchers published the results of a study they made of Tour de France cyclists in JAMA. [JAMA. 2003 May 21;289(19):2503-4.] These showed that administration of substances that inhibit the enzyme xanthine-oxidoreductase could protect athletes against injury. Allopurinol is one of these substances.
During exercise xanthine-oxidoreductase converts hypoxanthine is into xanthine first, and then into uric acid.
During this process aggressive molecules, such as superoxide, are released. These molecules can cause damage to the muscles and the heart, and increase the chance of injury or heart disease occurring. Allopurinol and its metabolite oxypurinol inhibit this process by inhibiting xanthine-oxidoreductase.
Because gout episodes are the result of excess uric acid in the blood, doctors use allopurinol as a medicine for gout. It has relatively few side effects and is not on the doping list.
By the way, there are natural alternatives for allopurinol. Phytate – in supplement form it goes by the name of inositol-hexakisphosphate – inhibits xanthine-oxidoreductase too [Life Sci. 2004 Feb 13;74(13):1691-700.], as do the flavonoids baicalein [structural formula shown here], wogonin and baicalin. [Anticancer Res. 1993 Nov-Dec;13(6A):2165-70.] These are found in extracts of plants such as Scutellaria baicalensis [which you may know as Skullcap].
The researchers performed an experiment, funded by the EU, on 12 male football players, all of whom played a match in the Spanish Football League. Half of the players were given a placebo four hours before the match, the other half were given 300 mg allopurinol. Just before the match and 12 hours afterwards the researchers analysed the players’ blood.
The effects of allopurinol were most visible after the match. The researchers found considerably less creatine-kinase [CK], lactate dehydrogenase [LDH] and myoglobin in the players that had been given allopurinol than those that had been given a placebo. CK, LDH and myoglobin are markers for muscle damage.
Markers for damage to the heart muscle are high sensitive troponinT [Hs TnT] and myocardial-kinase [CK-MB]. Allopurinol inhibited the rise in these two markers after the match too.
A classic marker for free-radical damage is the concentration of malondialdehyde in the blood. The effect of allopurinol on this marker doesn’t look like much, but it was statistically significant.
“Because allopurinol is such a safe drug, the possibility could be considered that players could be given allopurinol to prevent cardiac and skeletal muscle damage”, the researchers conclude. “The fact that professional players in the last decade have started playing three games a week (as opposed to earlier when they only played one every weekend) gives more strength to the preventive action of allopurinol for these individuals.”
Scand J Med Sci Sports. 2014 Apr 1. doi: 10.1111/sms.12213. [Epub ahead of print].