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being a sedative can reduce sexual drive and reduce erection. These effects are dose dependent and one will be able to get over these in a few days.
Since this is only going to be a short course, you may proceed to take them as suggested by your doctor. If these side effects persist for more than a week, talk to your doctor who can plan to start alternative muscle relaxants. So I do not think you need to be worried with this issue.
Hope this answers your query.