US researchers have discovered that correcting a chemical imbalance in US drug major Merck & Co’s analgesic Vioxx (rofecoxib) could counter its controversial side effects.

Merck voluntarily withdrew Vioxx in September last year after evidence linked its use to a substantially increased risk of heart attacks and stroke, causing its share price to plunge and throwing the safety of the whole class of COX-2 inhibitor drugs into question [[01/10/04a]]. Now, a US team at Duke University claims that taking low-dose aspirin alongside Vioxx might prevent these side effects, reports the journal Cell Metabolism.

Dr Thomas Coffman and colleagues at the University of North Carolina, Pennsylvania University and Durham VA Medical Center, investigated the chemical processes involved in the body’s response to COX-2 inhibitors, which were considered as stomach-friendly alternatives to the non-steroidal anti-inflammatory class of analgesics. Their research suggests that an enzyme called thromboxane may be responsible for the dangerous side effects of taking Vioxx. Therefore, adding aspirin to lower thromboxane might help avoid unwanted heart problems, they conclude.

Commenting on the findings, Dr Coffman noted that they indicate that: “therapies that block unrestrained thromboxane actions - for example, low doses of aspirin - might protect against end-organ damage without affecting blood pressure in patients taking COX-2 inhibitors.” However, he pointed out that unwanted gastrointestinal side effects from aspirin, such as bleeding, would still need to be closely monitored.

Dr Matthew Breyer, from Vanderbilt University Medical School in the USA, noted that “it may be possible to identify drugs that provide all the therapeutic effects of NSAIDs and COX-2 inhibitors but lack their adverse side effects,” according to BBC News online.

Since the withdrawal of Vioxx, the US drug giant has faced continuous accusations that its marketing of the drug was fraudulent and misrepresented its efficacy, and that it manipulated trials to boost the compound’s safety profile. Last month, a judge went against the US giant in the first civil trial, ruling that the firm was negligent in the death of Robert Ernst, who took Vioxx for tendonitis and died suddenly in his sleep, awarding his widow more than $250 million dollars [[22/08/05a]]. The decision could encourage a wave of additional lawsuits, sending the numbers sharply upwards from the current figure of 4,200; some estimates have been put at around 100,000 cases. But Merck has always defended its actions with regard to the agent, and this latest research may well provide a potential route for return to market for this one-time blockbuster.