Brief Answer:
Need to find out cause of poor response.

Detailed Answer:
Hello,
Thanks for your query.
I appreciate your efforts for medical consultation in so much distress.

Important aspects of your query are:
•     49 year old male
•     Known case of anxiety and nausea.
•     Currently on Mirtazapine for 33 days.
•     Complaints of: poor response to treatment.

Mirtazapine is good drug for anxiety specially in presence co existent gastric symptoms like nausea in your case. This drug take 4 to 6 weeks to show improvement after achieving the optimum dose for patient.

Apart from that common causes of poor treatment response:
•     Vitamin deficiency: Start multi vitamins (Specially vitamin B1, B12 and vitamin D)
•     Side effect of substance use (stop use if present)
•     Thyroid related problem: get thyroid hormonal assay done
•     Concurrent stress in life

In your case following steps will be helpful:
-Wait for 10-15 days for response
-Increase mirtazapine doses to 45 mg per day, if there is no response with current doses after 2 week, under your psychiatrist supervision.
-You can also start some benzodiezepines medicines (like clonazepam) for short term which immediately relieve anxiety symptoms under your psychiatrist supervision.

I hope this information has been both informative and helpful for you. In case of any doubt, I will be available for follow ups.

Wish you good health.
Regards,

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