"Theo" toxicity

Q: All of the following may occur with Theophylline overdose except? 

A) cerebral vasoconstriction 
B) hyperkalemia 
C) hyperglycemia 
D) metabolic acidosis 
E) arrhythmias


Answr: B

Most of the Theophylline effect occurs via antagonism of adenosine receptors and indirect adrenergic activity (see below). This effect is used for its primary use as a bronchodilator. In the case of overdose, it causes arrhythmias (choice E), cerebral vasoconstriction (choice A) and seizure. One of the dilemmas occurs when cardiac arrhythmia results in hypotension and need for vasopressor arises. Theophylline itself increases the level of epinephrine, norepinephrine, and dopamine via catecholamine elevation. In such scenarios, vasopressin may be a relatively safer choice, though no guideline or recommendation is available for this particular clinical situation.

At higher doses, theophylline acts as a phosphodiesterase inhibitor and increases the levels of cyclic adenosine monophosphate which augments beta-adrenergic activity. It results in hypokalemia, hyperglycemia, metabolic acidosis, and beta-adrenergic mediated vasodilatation.

#toxicology
#hemodynamic


References:

1. Minton NA, Henry JA. Acute and chronic human toxicity of theophylline. Hum Exp Toxicol 1996; 15:471. 

2. Shannon M. Hypokalemia, hyperglycemia and plasma catecholamine activity after severe theophylline intoxication. J Toxicol Clin Toxicol 1994; 32:41.