"The US Food and Drug Administration (FDA) today approved asfotase alfa (Strensiq, Alexion Pharmaceuticals) as the first-ever therapy for patients who develop hypophosphatasia, a rare metabolic bone disorder, in childhood.
(Generic versions may still be available.)
DOSAGE AND ADMINISTRATION
Effective use of theophylline (i.e.,the concentration of drug in the serum associated with optimal benefit and minimal risk of toxicity) is considered to occur when the theophylline concentration is maintained from 10 to 20 pg/mL. The early studies from which these levels were derived were carried out in patients immediately or shortly after recovery from acute exacerbations of their disease (some hospitalized with status asthmaticus).
Although the 20 µg/mL level remains appropriate as a critical value (above which toxicity is more likely to occur) for safety purposes, additional data are now available which indicate that the serum theophylline concentrations required to produce maximum physiologic benefit may, in fact, fluctuate with the degree of bronchospasm present and are variable. Therefore, the physician should individualize the range appropriate to the patients requirements, based on both symptomatic response and improvement in pulmonary function. It should be stressed that serum theophylline concentrations maintained at the upper level of the 10 to 20 pg/mL range may be associated with potential toxicity when factors known to reduce theophylline clearance are operative (see WARNINGS).
If it is not possible to obtain serum level determinations, restriction of the daily dose (in otherwise healthy adults) to not greater than 13 mg/kg/day to a maximum of 900 mg of anhydrous theophylline in divided doses will result in relatively few patients exceeding serum levels of 20 pg/mL and the resultant greater risk of toxicity.
Caution should be exercised for younger children who cannot complain of minor side effects. Older adults, those with cor pulmonale, congestive heart failure, and/or liver disease may have unusually low dosage requirements and thus may experience toxicity at the maximal dosage recommended below.
Theophylline does not distribute into fatty tissue. Dosage should be calculated on the basis of lean (ideal) body weight where mg/kg doses are presented.
Frequency of Dosing
When immediate-release products with rapid absorption are used, dosing to maintain serum levels generally requires administration every 6 hours. This is particularly true in children, but dosing intervals up to 8 hours may be satisfactory in adults since they eliminate the drug at a slower rate. Some children, and adults requiring higher than average doses (those having rapid rates of clearance, e.g., half-lives of under 6 hours) may benefit and be more effectively controlled during chronic therapy when given products with extended-release characteristics, since these provide longer dosing intervals and/or less fluctuation in serum concentration between dosing.
Dosage guidelines are approximations only and the wide range of theophylline clearance between individuals (particularly those with concomitant disease) make indiscriminate usage hazardous.
I. Acute Symptoms of Asthma or Bronchospasm Requiring Rapid Attainment of Theophylline Serum Levels
NOTE: Status asthmaticus should be considered a medical emergency and is defined as that degree of bronchospasm which is not rapidly responsive to usual doses of conventional bronchodilators. Optimal therapy for such patients frequently requires both additional medication, parenterally administered, and close monitoring, preferably in an intensive care setting.
A. Patients not currently receiving theophylline products:
|Children age 1 to under 9 years||5 mg/kg||4 mg/kg q 6 hours|
|Children age 9 to under 16 years; and smokers||5 mg/kg||3 mg/kg q 6 hours|
|Otherwise healthy nonsmoking adults||5 mg/kg||3 mg/kg q 8 hours|
|Older patients and patients with cor pulmonale||5 mg/kg||2 mg/kg q 8 hours|
|Patients with congestive heart failure||5 mg/kg||1-2 mg/kg q 12 hours|
B. Patients currently receiving theophylline products:
Determine, where possible, the time, amount, dosage form, and route of administration of the last dose the patient received.
The loading dose for theophylline is based on the principle that each 0.5 mg/kg of theophylline administered as a loading dose will result in a 1.0 µg/mL increase in serum theophylline concentration. Ideally, the loading dose should be deferred if a serum theophylline concentration can be obtained rapidly.
If this is not possible, the clinician must exercise judgment in selecting a dose based on the potential for benefit and risk. When there is sufficient respiratory distress to warrant a small risk, then 2.5 mg/kg of theophylline administered in rapidly absorbed form is likely to increase serum concentration by approximately 5 pg/mL. If the patient is not experiencing theophylline toxicity, this is unlikely to result in dangerous adverse effects.
Subsequent to the decision regarding use of a loading dose for this group of patients, the maintenance dosage recommendations are the same as those described above.
II. Chronic Therapy
Theophylline is a treatment for relief and/or prevention of symptoms from asthma and reversible bronchospasm associated with chronic bronchitis and emphysema. A dosage form that allows small incremental doses is desirable for initiating therapy. A liquid preparation should be considered for children to permit easier and more accurate dosage adjustment. Slow clinical titration is generally preferred to assure acceptance and safety of the medication, and to allow the patient to develop tolerance to transient caffeine-like side effects.
16 mg/kg/24 hours or 400 mg/24 hours (whichever is less) of anhydrous theophylline in divided doses at 6-or 8-hour intervals.
The above dosage may be increased in approximately 25 percent increments at 3-day intervals so long as the drug is tolerated, until clinical response is satisfactory or the maximum dose indicated in section III (below) is reached. The serum concentration may be checked at these intervals, but at a minimum should be determined at the end of this adjustment period.
It is important that no patient be maintained on any dosage that is not tolerated. When instructing patients to increase dosage according to the schedule above, they should be told not to take a subsequent dose if apparent side effects occur and to resume therapy at a lower dose once adverse effects have disappeared.
III. Maximum Dose of Theophylline Where the Serum Concentration is Not Measured
WARNING: DO NOT ATFEMPT TO MAINTAIN ANY DOSE THAT IS NOT TOLERATED.
|Not to exceed the following (or 900 mg, whichever is less):|
|Age 1 to under 9 years||24 mg/kg/day|
|Age 9 to under 12 years||20 mg/kg/day|
|Age 12 to under 16 years||18 mg/kg/day|
|Age 16 years or older||13 mg/kg/day|
IV. Measurement of Serum Theophylline Concentrations During Chronic Therapy
V. Final Adjustment of Dosage
Dosage adjustment after serum theophylline measurement
|If serum theophylline is:||Directions:|
|Within desired range||Maintain dosage if tolerated.|
|Too high||20 to 25 µg/mL||Decrease doses by about 10% and recheck serum level after 3 days.|
|25 to 30 pg/mL||Skip the next dose and decrease subsequent doses by about 25%. Recheck serum level after 3 days.|
|Over 30 pg/mL||Skip next 2 doses and decrease subsequent doses by 50%. Recheck serum level after 3 days.|
|Too low||Increase dosage by 25% at 3- day intervals until either the desired serum concentration and/ or clinical response is achieved. The total daily dose may need to be administered at more frequent intervals if symptoms occur repeatedly at the end of a dosing interval.|
The serum concentration may be rechecked at appropriate intervals, but at least at the end of any adjustment period. When the patient's condition is otherwise clinically stable and none of the recognized factors that alter elimination are present, measurement of serum levels need be repeated only every 6 to 12 months.
|100 mg tablets||Bottles of 100||0075-0351-68||White||Rhone-Poulenc Rorer Logo |
|200 mg tablets||Bottles of 100||0075-0352-68||White||Rhone-Poulenc Rorer Logo |
|80 mg/15 mL nonalcoholic syrup||16 FL OZ||0075-3650-16||Pink|
STORAGE CONDITIONS: Store at room temperature. Protect from excessive heat, light and moisture.
Caution: Federal law prohibits dispensing without prescription.
KEEP THIS AND ALL MEDICATIONS OUT OF THE REACH OF CHILDRENThis monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 12/8/2004
Additional Slo-phyllin Information
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