I like clamps Have a look at 74S1053
I would not use a 'S' chip
Regular HC(T) chips can clamp 20mA either way and with the filter I suggested exceeding that is extremly unlikely. I recommend using a schmitt chip (e.g a -14) to handle the slower rise/fall time the cap introduces.

I have no idea what the 'S' chip Richard suggest can clamp, but 20mA is more than sufficient when preceeded by 'my' filter.

that series resistor should be valuable in limiting the voltage to legal levels I like the capacitor to reduce the risetime, clamps need a few nanoseconds to react, and I can visualize a heavy spike getting past that if no cap.

Erik