Was the ciprofloxacin prescribed for YOU for a sinus infection that was diagnosed by your medical provider? If so, you would need to have the right dosage and amount, based on your weight and severity of infection. These are usually decided at the time you are being examined.
If you are self-diagnosing and using a past prescription prescribed for a different medical reason, or if you are being furnished with with a prescription from someone else, I would strongly caution you against self-treatment in this manner.
Incidentally, most cases of sinusitis are VIRAL and do not require antibiotics.
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