I would suggest you try Arthri-aid as the next best thing. It is designed to help joints in the best way possible without using prescription drugs.
It might not be as good though. Loxicom contains the drug meloxicam, which belongs to the NSAID group of drugs. These drugs tend to be very toxic to cats, especially if given repeatedly. Meloxicam is unusual in that cats seem to be able to tolerate this drug very well, and so can benefit from the great help it can provide. All forms of meloxicam (Metacam was the original brand) are prescription only.
Non-prescription medications for this type of problem tend to be herbal, homeopathic or nutraceuticals and they are much less effective. Weight control and things like acupuncture can be of some benefit. Most people end up paying their vets for a prescription, and buying the best medication if the cat really needs it.