Once your toothbrush has served the main purpose of cleaning your teeth, there’s no need to dispose of it straight away. There’s plenty of other uses for it!
First of all, boil it in hot water for a few minutes to sanitize it. If you want to make the most of it while the bristles are still semi-functional, you can use it as a brow comb, or to maintain electronics (like cleaning your laptop keyboard, removing debris from the hairdryer, etc) or simply use it to clean small surfaces and corners.
If the bristles will no longer be of any purpose go ahead and pull the bristles out with pliers, throw them away with the plastic recycling, and use your imagination. We are making garden markers with our old bamboo toothbrushes.
Lastly, you can compost the handle, it is 100% biodegradable.