British regulators recommended on Monday that physicians restrict the use of the anti-depressant Efexor (search) from drugmaker Wyeth because its use could have side effects for heart health and pose other potential risks that require more careful monitoring than other drugs in the class.

Wyeth said it would challenge the decision, but its shares slipped 3 percent.

The United Kingdom's Medicines and Healthcare Products Regulatory Agency said the drug, which is marketed as "Effexor" in the United States, may cause irregular heart rhythms, withdrawal symptoms and have a higher rate of death from overdose than similar drugs.

The agency is recommending that only specialists should prescribe Efexor and that patients should be continually supervised. The drug should also not be prescribed to patients with heart problems, the agency said.

In a statement, Wyeth said it will challenge the agency's action and urged it to accept the company's previous recommendations for labeling, educational initiatives and new packaging to reduce the risk of suicide and overdose.

The anti-depressant is the Madison, N.J.-based pharmaceutical company's best-selling drug.

Wyeth shares were down $1.20, or 2.9 percent, $40.36 in afternoon trading on the New York Stock Exchange.