1 Answer

Call your doctor at once if you have a serious side effect such as:

confusion, hallucinations, unusual thoughts or behavior;
weak or shallow breathing;
unusual risk-taking behavior, no fear of danger;
unusual or involuntary eye movements;
pounding heartbeats or fluttering in your chest;
painful or difficult urination, urinating less than usual;
pale skin, easy bruising or bleeding; or
new or worsening seizures.

Less serious side effects of clonazepam may include:

drowsiness, dizziness, problems with thinking or memory;
tired feeling, muscle weakness, loss of balance or coordination;
slurred speech, drooling or dry mouth, sore gums;
runny or stuffy nose;
loss of appetite, nausea, diarrhea, constipation;
blurred vision;
headache;
sleep problems (insomnia);
skin rash; or
weight changes. 

Source http://www.drugs.com/sfx/klonopin-side-effects.html