If you're looking for a nutritional supplement that has been formulated with feline health in mind‚ Rx Vitamins for Pets' Rx Essentials for Cats Powder may be right for you and your pet. First‚ this powder contains a wide array of vitamins and minerals. For example‚ vitamin A might work to maintain optimal night vision (which is important because cats are largely nocturnal animals)‚ while potassium is involved in regulating muscle function.