Some antacids interact with Plavix more

Taking the blood thinner Plavix along with some prescription antacids can reduce the effectiveness of the blood clot prevention, Health Canada says.

The department sent an advisory to health professionals and patients on Thursday warning that new evidence showed whilesomeantacids called proton pump inhibitors interact with Plavix, not all reduce the effectiveness to the same degree.

Plavix, known generically as clopidogrel, is a prescription blood thinner used to preventblood clotsthat could lead to heart attack or stroke. It is given to patients with a history of heart-related problems.

Proton pump inhibitors or PPIs are prescription antacids used to treat heartburn and stomach ulcers, which can occur as side-effects of Plavix.

"New studies have shown that, while PPIs dointeract with Plavix, not all PPIs interact to the same degree: some have a strong effect on Plavix, while others do not," Health Canada said in a statement.

The labelling for Plavix has been updated with new recommendations regarding the use of PPIs:

• PPIs known to strongly or moderately reduce Plavix effectiveness should be avoided. Omeprazole (sold in Canada as Losec) is one of these.
• If a PPI must be used in a patient taking Plavix, consider a PPI that does not interact as strongly. Pantoprazole (sold as Pantaloc) is one of these.

In 2009, labels on Plavix were updated to indicate that use of any PPI in patients taking the drugshould be discouraged, as emerging data suggested that PPIs potentially reduced the ability of Plavix to protect against blood clots.

The latest update was based on studies that showed not all PPIs interact with Plavix equally, Health Canada said.

These proton pump inhibitors sold in Canada:

• Dexlansoprazole (sold under the brand name Dexilant.
• Esomeprazole (sold under the brand name Nexium and its generic equivalent).
• Omeprazole (sold under the brand name Losec and its generic equivalents).
• Lansoprazole (sold under the brand name Prevacid and its generic equivalents).
• Pantoprazole (sold under the brand names Pantoloc and Panto IV, and their generic equivalents).
• Pantoprazole/magnesium (sold under the brand name Tecta).
• Rabeprazole (sold under the brand name Pariet and its generic equivalents)

PPIs are also available in combination with other drugs, such as Vimovo, which contains esomeprazole.