## Example: Maintenance Dose Calculation – KATZUNG

Plasma concentration of theophylline target of 10 mg / L is desired to relieve acute bronchial asthma in a patient. If the patient is a nonsmoker and otherwise normal, except for asthma, we can use the mean clearance given in Table 3-1, ie 2, 8 L/h/70 kg. Since the drug is administered intravenously, F = 1. Therefore, in this patient, the infusion rate would be appropriate mg/h/70 28 kg. If the asthma attack is relieved, the clinician may wish to maintain this level of plasma using oral theophylline, which may be given every 12 hours using a sustained-release formulation to approximate a continuous intravenous infusion. According to Table 3-1, Foral is 0.96. When the dosing interval is 12 hours, the size of each maintenance dose would be: One size of tablets or capsules close to the ideal dose of 350 mg then be prescribed to 12 hours apart. If a dosing interval of 8 hours was used, the ideal dose is 233 mg, and the drug was administered once daily, the dose is 700 mg. In practice, F may be omitted in the calculation because it is so close to 1.