Its good that you spit out as much as possible.Side effects depends on the amount of methadone you have consumed.
Some of the immediate effects will be behavioral restlessness
, tremulousness and hyperactivity. It is also associated with mood changes like euphoria and intense pleasure.
Some of the other symptoms which might occur later are Constipation
, sweating, Sedation and Hypotension
In case of Overdose – Miosis, Respiratory Depression
, Coma can occur.
But I don't think you have overdosed.
In that case you can expect some of the above said side effects.