Compound Sulfamethoxazole Tablets is a compound preparation of sulfamethoxazole and methotrexate. The dosage is generally divided into adult usual dosage, adult preventive dosage, pediatric usual dosage and so on. 1. Adult usual dosage: Adult usual dosage for the treatment of bacterial infections, once methotrexate 160mg and sulfamethoxazole 800mg, once every 12 hours. For the treatment of Pneumocystis carinii pneumonia, once methotrexate 3.75~5mg/kg and sulfamethoxazole 18.75~25mg/kg, every 6 hours. 2. Adult preventive dosage: 160mg of methotrexate and 800mg of sulfamethoxazole twice a day, followed by the same dosage once a day, or three times a week. 3. Pediatric dosage: prohibited for infants under 2 months. For the treatment of bacterial infections, infants over 2 months old and weighing less than 40kg should be given methotrexate 20-30mg/kg and sulfamethoxazole 4-6mg/kg orally according to their body weight once every 12 hours; the dosage for children weighing 40kg should be the same as that for adults. Sulfamethoxazole tablets also have certain side effects, some patients may experience nausea, vomiting, headache, fatigue and other adverse reactions. Remember that it is forbidden for pregnant women, lactating women and those with severe liver or kidney impairment. It is recommended that patients should take Fosfon Sulfamethoxazole Tablets under the guidance of a doctor and should not use the medicine privately.