Theophylline blood levels in Sri Lankan asthmatics: comparison of two methods of assay.
OBJECTIVE
To assay theophylline blood levels in a sample of Sri Lankan chronic asthmatics taking oral theophylline, and to evaluate a simple and cost effective ultraviolet spectrophotometric assay for theophylline levels in blood.


METHODS
Chronic asthmatics taking oral theophylline attending medical clinics at the National Hospital of Sri Lanka (NHSL) were recruited for the study. Blood samples were collected from recruited patients on their subsequent clinic visit.


METHODS
A cross-sectional study of theophylline blood levels. Blood samples were assayed for trough theophylline levels using two methods: an automated homogeneous enzyme immunoassay (EMIT), and a low cost ultraviolet spectrophotometric method.


RESULTS
Only 2 patients of the 24 had theophylline blood levels in the accepted therapeutic range (10 to 20 micrograms/ml) (3.4); 19 patients had levels under 5 micrograms/ml. A correlation coefficient of 0.99 was obtained in the statistical comparison of the two methods, indicating that the spectrophotometric method has similar accuracy as the reference EMIT assay.


CONCLUSIONS
The results signal a need for monitoring of theophylline in asthmatics when accepted clinical indications are present. The ultraviolet spectrophotometric method is ideal to initiate therapeutic drug monitoring (TDM) in the country because of its low cost (about Rs. 55 per assay), requiring only a UV recording spectrophotometer.
Department of Pharmacology, University of Sri Jayawardenapura, Nugegoda. akeg@sltnet.lk
A K E
AK
Goonetilleke
T M J
TM
Munasinghe
H C
HC
Cooray
W K
WK
Balasuriya
N
N
Fernando
D000328:Adult; D000368:Aged; D001249:Asthma / Q000097:blood* / Q000188:drug therapy; D001993:Bronchodilator Agents / Q000097:blood* / Q000493:pharmacokinetics; D003430:Cross-Sectional Studies; D016903:Drug Monitoring; D017248:Enzyme Multiplied Immunoassay Technique; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013056:Spectrophotometry, Ultraviolet; D013806:Theophylline / Q000097:blood* / Q000493:pharmacokinetics
D001993:Bronchodilator Agents; D013806:Theophylline