After neuter how long should I wait to give him my cat Frontline plus spot on flea treatment? And can someone tell me the dosage of this product according to weight?
There's a single use dose inside for all cats over 8 weeks / 1 kg. So you will need to put the contents of it onto him. There are videos on frontline website and YouTube on how to best administer these and where to place it if you haven't done it before.
I don't think you would have to wait because of the neutering per se, unless he has just come home and is feeling out of it, you may not want to stress him with it right away.
Has he had it before? In that case you'd have to wait the time since last application (1month).