Zyrtec D Mail Order is in a drug class called muscarinic receptor antagonist that reduces spasms of smooth muscles For oral dosage form (tablets): Adults—At first, 2 milligrams (mg) two times a day. Detrol: Tolterodine belongs to a group of medications known as antispasmodics and anticholinergics. 5/10 Before Taking This Medicine You should not use Detrol if your are allergic to tolterodine or fesoterodine (Toviaz), or if you have: 1. By relaxing the muscles in the bladder, tolterodine improves your ability to control your urination.">Zyrtec D Mail Order is in a drug class called muscarinic receptor antagonist that reduces spasms of smooth muscles For oral dosage form (tablets): Adults—At first, 2 milligrams (mg) two times a day. Detrol: Tolterodine belongs to a group of medications known as antispasmodics and anticholinergics. 5/10 Before Taking This Medicine You should not use Detrol if your are allergic to tolterodine or fesoterodine (Toviaz), or if you have: 1. By relaxing the muscles in the bladder, tolterodine improves your ability to control your urination.">