Despite the frequency of acute poisoning in normal children by oral or rectal phosphosoda laxatives, the rate of clearance of the resultant high level of phosphorus and the rationale for therapy are defined incompletely. 1 Pharmacokinetic analysis has been made of plasma inorganic phosphate ( Pi) in an infant after ingestion of phosphosoda laxative and of data reported for four comparable poisonings in healthy infants to provide a nomogram which predicts the decline in Pi in paediatric phosphate poisoning. 2 Clearance of Pi is exponential; it directly correlates with and approaches the glomerular filtration rate. 3 After single oral or rectal overdoses, plasma Pi at diagnosis is 4-20 mmoul and has a half-life of 5-11 h that appears independent of therapy. The time for plasma Pi to return to normal can be calculated from the initial Pi as t = (In 5/ Pi )/0.1292. 4 Neuromuscular and cardiac abnormalities relate to the low serum calcium; the increase of total serum calcium during recovery from phosphate poisoning is linear but is accelerated by intravenous (i.v.) calcium salt. Continued i.v. calcium therapy may be required since restoration of plasma calcium is often delayed.
A sustained-release theophylline (SRT) tablet was evaluated in 15 children with moderately severe asthma between the ages of 3 and 5 years (4.2 +/- 0.83 years). They received a mean daily dose of 20.4 mg/kg given q12h for 3 or more weeks with daily symptom scores and twice daily peak flow rates (PFR) measured. Serum theophylline levels (STL) were then obtained at 0, 1, 2, 4, 6, 8, 10, and 12 hr (eight children had 24-hr samples obtained), along with PFRs every 3 hr. The mean peak STL (x +/- SD) was 16.6 +/- 4.4 and the trough was 5.9 +/- 2.8, with a peak-trough difference of 10.6 +/- 3.9. The average time to peak level was 3.9 hr. The mean +/- SD clearance was 1.42 +/- 0.63 ml/kg per min and the apparent T1/2 was 5.11 +/- 1.34 hr. The average weekly morning PFR for the 3-week period ranged from 116.8 +/- 41.2 to 127.4 +/- 37.4 L/min, and the evening PFT ranged from 126.5 +/- 38.4 to 137.0 +/- 40.9 L/min. In conclusion, the SRT tablet is effective in treating many young asthmatics on a 12-hr dosage schedule. For some children who experience excessive peak-trough differences, an 8-hr dosage schedule may be indicated.
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