###Human: Can Levosulpiride and Flupenthixol cause low sexual drive? ###Assistant: Hi. I have read and understood your problem. Levosulpiride and Flupenthixol can cause problem with erection. This is the cause of erectile dysfunction in your case. Sildenafil citrate (Viagra) is usually prescribed at a dose of 50 mg three hours before sex. But, should be taken after clinical checkup including blood pressure.