Some side effects with Stalevo are potentially serious and should be reported immediately to your healthcare provider. Although most of these serious side effects are rare, a few may be common. Many of these side effects have occurred with carbidopa-levodopa products, which have been available for a long time, and are expected to also be a problem with Stalevo, which contains carbidopa-levodopa in combination with entacapone. These serious side effects of Stalevo (or of carbidopa-levodopa alone) include but are not limited to: