Patients who are taking orphenadrine citrate may experience common or serious side effects. If serious side effects occur, they should contact a doctor immediately. Common side effects include drowsiness, constipation, dizziness, dry mouth, lightheadedness, upset stomach, blurred vision, headache, and vision changes. The serious side effects include mood/mental changes, eye pain, shaking, trouble urinating, fainting, and pounding/fast heartbeat.