Metformin is a biguanide antidiabetic. This eMedTV Web page also includes metformin dosing guidelines for. The recommended starting dosage for children ages 10 to 16 is metformin. Metformin hydrochloride, or HCL, is an oral medication available by prescription. The medication works along with a proper diet and exercise to lower. Page 1 of 22 Metformin Hydrochloride Extended. Mg Rx only DESCRIPTION Metformin hydrochloride extended. Diabetic drug sometimes used to treat PCOS. This page will answer your questions.