Obagi Medical Products Inc. announced Tuesday an expansion of its relationship with Rohto Pharmaceutical Co. Ltd., a manufacturer of over-the-counter personal care products and Obagi’s marketing and distribution partner in Japan.

Long Beach-based Obagi makes therapeutic skin care products that in the United States are primarily distributed in doctors’ offices. One product is Elastiderm, which was originally formulated for use by plastic surgeons and dermatologists before and after procedures.

Obagi and Rohto will launch a series of products using Obagi’s Elastiderm technology into additional distribution channels, including premium drug and variety stores. They also will jointly develop other skin care products for the Japanese market.

Under an existing agreement, Rohto manufactures and distributes Obagi-branded Vitamin C, Platinum and Triple Peel products in Japan.

Obagi shares were up 20 cents, or 3 percent, to $7.05 in morning trading on the Nasdaq.