Hoshi was most well-known for its medicines intended for the consumer market called baiyaku, which literally means "sold medicines" and is often translated as patent medicines. The sale of patent medicines depended upon the creation of difference and demand, and patent medicine manufacturers were among the earliest and most aggressive manufacturers in the history of modern advertising in Japan. Similar to their Euro-American counterparts of the time, baiyaku often gained disrepute for their ornate packaging and attention-grabbing advertising that exaggerated their medicinal properties. In Japan, as elsewhere, baiyaku often represented the opposite of the professionalization of modern medicine.

Yet, as scholars such as Susan Burns have shown, medicine manufacturers responded by portraying baiyaku as scientific and supplemental to professional medical care and by re-branding them with the neologism, katei-iyaku or "medicines for the home." Working within trends that favored scientific, rational, and ethical medicine, patent medicine makers advertised their products as distinctly modern and scientific preventative and therapeutic commodities. Instead of advertising patent medicines as panaceas for a plethora of pains, patent medicines specialized and proliferated: almost any ailment or bodily defect could be treated with a specific tonic, tincture, or powder that was easily within reach.

Popular medicines advertised by Hoshi included Hoshi Ginseng Quinine Wine (Hoshi ninjin kina budōshu), Hoshi Children's Medicine (Hoshi shōni gusuri), and Hoshi Cold Pills (Hoshi ganbōjō). But no medicine was advertised more than the famed Hoshi Digestive Medicine (Hoshi ichōyaku). Its packaging was so iconic that it became the subject of multiple copycats and trademark disputes.  Known as the "red can" (aka kan) for its iconic packaging, the Digestive Medicine was not just its most profitable medicine, but also a metonym for the company itself, representing its efforts to sell modern medicines in the name of Japan's civilizing mission, both at home and abroad.

The two major active ingredients, magnesium carbonate and sodium bicarbonate, comprised 93.565% of the compound and gave the medicine its powdery white consistency. Although these ingredients may seem mundane—the former is the active ingredient in Tums and Alka-Seltzer, and the latter is simply common baking soda—they were two of the most frequently tested and prescribed alkali salts in the early twentieth century, and they were new and perhaps even novel for their times (indeed, Tums and Alka-Seltzer did not reach the market until the early 1930s). But like all proprietary medicines, it also contained a special mixture of herbal ingredients such as menthol (mentooru), cinnamon oil (keihi yu), cinnamon powder (keihi matsu), colombo powder (koronbo matsu), gentian power (genchiana matsu), and ginger powder (shōkyō matsu). Consumers were directed to dissolve the white, grainy powder in water and then ingest the suspension.

The image below depicts a variety of new ideas for signs used to advertise Hoshi's medicines, from a cloth sign adorned with a sumo wrestler advertising Hoshi's Digestive Medicine (Hoshi ichōyaku) to a hanging metal sign for Hoshi's Eye Medicine (Hoshi meyaku).