Some companies produce GS in tablet form. Is this form safe / effective?

Yes, at least one company in China also produces the oral form GS-441524, which it claims will work just like injections. This is not surprising, since the modifications required to convert injectable drugs into an oral form are well known. All drugs for HIV / AIDS and hepatitis C were also transformed into an oral form. However, like many others, you may find it more difficult to give tablets to cats than to inject. They usually adapt to the injections over a short period of time, but if they don't agree with the pills, it still gets worse and worse. Therefore, if you go this route, do not invest much in it until you are sure that you will be able to give the tablets to your cat.