OBJECTIVES: While generic drug use has become more common with the availability of generic alternatives to the many high volume branded products, the rate at which generic drugs have displaced branded counterparts is not well understood, particularly when time-release (TR) brands are introduced within a similar timeframe. We examined the uptake of generic drugs with respect to products and classes in conjunction with the uptake of time-release formulations of branded products to determine the impact of generic uptake on branded drugs, particularly when a branded time-release formulation is launched prior to generic competition. METHODS: SSRIs, atypical antipsychotics, nonbenzodiazepines as well as azythromycin were selected as case classes and products. From 1995 to 2009 the volume of prescriptions were collected monthly using SDI’s VONA databases and grouped according to branded and generic sales by active molecule. RESULTS: Among SSRIs, brands that launched TR branded products at least one-year prior to the launch of the original formulation generic, such as paroxetine, saw less erosion of the total brand than those with  TR  launch less than one year or no TR launch. Similarly, among nonbenzodiazepines, early launch of TR formulation resulted in less erosion from the total brand. In cases where branded utilization is not converted to TR formulation prior to launch of generic competition, such as risperidone and fluoxetine, or TR launch precedes generic launch by less than six months or not at all, such as azythromycin and sertraline, dramatic reduction in total sales brand was observed. In the unique case where branded escitalopram was introduced prior to the generic launch of citalopram, an effect similar to a branded TR launch was observed. CONCLUSIONS: While generic use typically replaces the majority of branded equivalents in a short timeframe, branded products with a time-release formulation may limit uptake rate of the generic version of the total branded product.