These days the U.S. Food and Drug Administration (FDA) is taking no chances when it comes to the safety of new drugs.
The increased scrutiny required before new drugs are approved is the result of a series of safety scares over the last decade, in particular the recent one over the diabetes drug Avandia produced by Wyeth and Merck's painkiller Vioxx in 2004.
The FDA's tough stance has seen four out of five attempts by drug company Wyeth, to launch new medicines on the U.S. market to be delayed.
The latest blow from the FDA comes as the agency now says it is reviewing the safety of its biggest seller, Nexium, and Prilosec.
The FDA is more likely nowadays to issue companies with "approvable" letters, which set conditions rather than granting final approvals.
This delays the launch of a new drug, which has financial implications for a company.
The FDA says a preliminary review of new data on the safety of two stomach drugs Prilosec and Nexium suggests that long term use of these medications does not lead to heart attacks and other heart related events.
In two studies involving patients with severe GERD who were randomly assigned to receive surgery or drug treatment (Prilosec), there were apparently more heart attacks, heart failure and heart related sudden deaths among the drug patients compared with the surgery patients.
The other study on Nexium (esomeprazole), has now gathered 5 years of follow up on patients but is not yet completed.
The initial results also showed a difference between the drug treatment and the surgery group, similar to the Prilosec study, but a more recent update has since shown that the incidence of cardiovascular events is largely similar between the two groups.
However the agency says a final decision and recommendation will not be made for three months's time.
At this point the FDA advises doctors and patients not to change their current practice with regard to their use of these drugs.
Prilosec and Nexium are proton pump inhibitors (PPIs) used to control stomach acid and are taken by patients with a range of gastrointestinal conditions such as ulcers and gastroesophageal reflux disease (GERD).
Some GERD conditions erode the lining of the food pipe (esophagus) and PPIs help to heal the erosions or stop them getting worse; Prilosec and Nexium are available in the U.S. by prescription, although Prilosec is also dispensed over the counter for heartburn.
Another Wyeth drug Pristiq for the treatment of menopausal hot flushes, is still awaiting approval and has been delayed by regulators for at least a year over safety concerns, pending a further trial.
Experts say the FDA has become more concerned and vocal about safety issues but some critics suggest the caution is overzealous and the result of political pressure.
The FDA says it's current position on Prilosec and Nexium is based on all the information they have available and the preliminary conclusion is that the observed difference in risk of heart attacks and other heart related problems seen in early analyses of the two small long-term studies is not a true effect.