THe characteristics and costs of severe theophylline toxicity in a tertiary critical care unit in Eastern Cape Province, South Africa

Severe theophylline toxicity requiring haemodialysis accounts for approximately one-third of drug toxicity cases admitted to the Livingstone Tertiary Hospital (LTH) intensive care unit (ICU) in Gqeberha, South Africa, imposing a significant resource burden.Objectives. To investigate the characteristics and burden of severe theophylline toxicity in an Eastern Cape Province tertiary hospital adult ICU.Methods. A retrospective review of all severe theophylline toxicity admissions to the ICU from 1 January 2013 to 31 December 2018 was conducted. Demographic and clinical data were captured and analysed. The National Department of Health 2019 fees schedule was used to calculate costs based on duration of ICU stay and number of haemodialysis sessions received.Results. Of the 57 patients included in the study, 84% were cases of deliberate self-harm. The majority were aged <40 years (77%) and female (79%). The mean (standard deviation (SD)) initial serum theophylline level was 612 (269) µmol/L. Complications included convulsions (n=12; 21%), arrhythmias (n=9; 16%), need for mechanical ventilation (n=7; 12%) and death (n=4; 7%). The main risk factors for these complications were age ≥30 years, an inappropriately normal or elevated initial serum potassium level, an elevated serum creatinine kinase level and an elevated initial serum theophylline level. Receiver operator characteristic curve analysis assessing the initial serum theophylline level as a discriminator for life-threatening complications produced an area under the curve of 0.71 for serum theophylline >400 µmol/L (sensitivity 88%, specificity 12%). All the 4 patients who died had an initial serum theophylline level >1 000 µmol/L. The mean (SD) cost per admission amounted to ZAR16 897 (10 718), with a mean of one 4-hour dialysis session per admission.Conclusion. Severe theophylline toxicity, usually in the context of deliberate self-harm, is a preventable yet life-threatening toxicity encountered at LTH. Demographic risk factors include young females from certain areas in and around Gqeberha. Risk factors for complications include older age, paradoxically normal or elevated serum potassium levels, elevated serum creatinine kinase levels and an initial serum theophylline level >400 µmol/L. Patients with these clinical features should be closely monitored and treated timeously at an appropriate level of care. The need for ICU admission and dialysis, both limited resources, makes the treatment of severe theophylline toxicity costly. Further studies of the underlying psychosocial drivers, local prescribing practices and preventive interventions related to severe theophylline toxicity are required.

Estimation of the release profiles of multi-unit dose tablets of theophylline from the release profiles of their components

Purpose: The objective of this study is to investigate whether the drug release profile of a multi-unit dose form consisting of fast and slow release components can be predicted from the release profiles of their components by simple summation. Method: The fast release component consisted of conventional granules of theophylline made by wet massing the drug powder with starch mucilage (20w/v). The slow release component consisted of matrix granules of the drug made by triturating the drug powder with melted carnuba wax (i.e. melt granulation). Each type of granules was compressed to tablets of weight 100; 150 or 200mg. To form the multi-unit dosage tablets of drug content 300mg each; the conventional and matrix granules were mixed in the ratio 1:2; 1:1 and 2:1; and compressed. The tablets were subjected to dissolution test and from the experimental release curve the prompt release (mp) in the first 1h; the maximum release (m ) and the time to attain it (t ) were obtained. Result: For a given composition of the multi-unit dose tablets; the theoretical release curve was obtained by summation of the release from each component at the different time intervals. The mp values of the theoretically estimated release curves were generally higher; while their t values were generally shorter than the corresponding values for the experimental curves. Conclusion: The indication is that drug release from the multi-unit dose tablets was more retarded than could be theoretically estimated. Apparently; the two components interfere with each other's release