Hi & Welcome. Yes, it s quite common during first few days of treatment. Basically used as an antidepressant Zispin (Mirtazapine) is known to cause dizziness, feeling sleepy, or tired. These side effects are usually seen in the first few days of treatment and disappear gradually. Since you have been working for Health, Safety, and the Environment (HSE), do not drive or use tools or machines or drink alcohol as it may interfere with your motor activities. To avoid these problems, take the tablet once daily at bed time and remember it may take between two to four weeks for the benefits (antidepressant effects) of Mirtazapine to appear, so it is very important that you keep taking it, even if it doesn t seem to make much difference at first. Hope this will help you.