DOSAGE AND ADMINISTRATION Adults and children weighing over 20 Kg: For genitourinary or gastrointestinal tract infections other than gonorrhea in men and women , the usual dose is 500 mg q.i.d. in equally spaced doses; severe or chronic infections may require larger doses. For the treatment of gonorrhea in both men and women, a single oral dose of 3.5 grams of ampicillin administered simultaneously with 1 gram of probenecid is recommended. Physicians are cautioned to use no less than the above recommended dosage for the treatment of gonorrhea. Follow-up cultures should be obtained from the original site(s) of infection 7 to 14 days after therapy. In women, it is also desirable to obtain culture test-of-cure from both the endocervical and anal canals. Prolonged intensive therapy is needed for complications such as prostatitis and epididymitis. For respiratory tract infections , the usual dose is 250 mg q.i.d. in equally spaced doses. Pediatric Patients weighing 20 Kg or less: For genitourinary or gastrointestinal tract infections , the usual dose is 100 mg/kg/day total, q.i.d. in equally divided and spaced doses. For respiratory tract infections , the usual dose is 50 mg/kg/day total, in equally divided and spaced doses three to four times daily. Doses for children should not exceed doses recommended for adults. All patients, irrespective of age and weight: Larger doses may be required for severe or chronic infections. Although ampicillin is resistant to degradation by gastric acid, it should be administered at least one half-hour before or two hours after meals for maximal absorption. Except for the single dose regimen for gonorrhea referred to above, therapy should be continued for a minimum of 48 to 72 hours after the patient becomes asymptomatic or evidence at bacterial eradication has been obtained. In infections caused by haemolytic strains of streptococci, a minimum of 10 days' treatment is recommended to guard against the risk of rheumatic fever or glomerulonephritis (see PRECAUTIONS , Laboratory Tests ). In the treatment of chronic urinary or gastrointestinal infections, frequent bacteriologic and clinical appraisal is necessary during therapy and may be necessary for several months afterwards. Stubborn infections may require treatment for several weeks. Smaller doses than those indicated above should not be used. Directions for mixing Oral Suspension Prepare suspension at time of dispensing. For ease of preparation, add water to the bottle in two portions and shake well after each addition. 125 mg/5 mL Add a total of 86 mL to the 100 mL package and 170 mL to the 200 mL package. This will provide 100 mL and 200 mL of suspension. Each 5 mL (teaspoonful) will contain ampicillin trihydrate equivalent to 125 mg ampicillin. 250 mg/5 mL Add a total of 70 mL to the 100 mL package and 139 mL to the 200 mL package. This will provide 100 mL and 200 mL of suspension . Each 5 mL (teaspoonful) will contain ampicillin trihydrate equivalent to 250 mg ampicillin.