Apr 12, - Like most drugs, Ativan (lorazepam) does have various side effects that can be unpleasant or dangerous. Benzodiazepine drugs are commonly. Lorazepam Side Effects by Likelihood and Severity. COMMON side effects Muscle Weakness. If experienced, these tend to have a Less Severe expression. Common side effects of Ativan include: Drowsiness. Dizziness. Tiredness. Muscle weakness. Headache. Blurred vision. Sleep problems (insomnia) Loss of balance or coordination.