There is no known reason that Petromalt is bad for your cat. If you have concerns and want to try something more natural try feeding your cat canned pumpkin and use a deshedding tool. This tool grabs a lot more hair than just brushing.
Petromalt is a remedy for hairballs. It's not contraindicated unless your veterinarian has told you not to give it to your cat due to some other condition. Don't give more than the recommended amount since it's a laxative. Call your vet to double check since s/he knows your cat's history.
yes it is safe but always read the back of the product to see the amount that you need to give your cat. I would as well consult to see just how much you can give your cat do to its age.
Petromalt is a hairball remedy designed for cats. Before giving this remedy, you'll want to rule out other health issues, such as thyroid problems, which often occur in elderly cats.