Emergency Medicine

Tox icolog y 181

SPECIFIC POISONS

Theophylline

DIAGNOSIS

1 Theophylline toxicity may result from acute ingestion or chronic use. Both
are associated with significant morbidity and mortality.
(i) Chronic ingestion is exacerbated by intercurrent illness or the
concomitant administration of drugs that interfere with hepatic
metabolism.

2 Clinical manifestations include:
(i) Gastrointestinal tract: nausea, abdominal pain, intractable
vomiting.
(ii) Cardiovascular: sinus tachycardia, hypotension and cardiac
arrhythmias.
(iii) CNS: anxiety, agitation and insomnia.
(iv) Hyperventilation, gastrointestinal bleeding, convulsions, coma
and ventricular tachycardia in severe toxicity.

3 Clinical signs of significant toxicity may be delayed by up to 12 h in acute
overdose, when sustained-release tablets have been ingested.

4 Gain i.v. access and send bloods for U&Es, LFTs, blood sugar and a theophyl-
line level.
(i) Look for hypokalaemia, hypomagnesaemia, hyperglycaemia and
metabolic acidosis, particularly in severe acute ingestions.

5 Determine the serum theophylline level.
(i) Acute poisoning:
(a) toxic symptoms occur with a theophylline level over 25 mg/L
(b) levels of 40–60 mg/L are serious, and a level >80 mg/L is
potentially fatal.
(ii) Chronic toxicity:
(a) levels over 20 mg/L cause symptoms, and over 40 mg/L may
be life-threatening.

6 Perform an ECG and cardiac monitoring. Cardiac arrhythmias are common
and include sinus tachycardia, supraventricular tachycardia, atrial f lutter
and VT.

MANAGEMENT

(^1) Ensure the airway is secure and administer high-f low oxygen. Correct f luid
depletion and hypokalaemia with normal saline and potassium under ECG
monitoring.
2 Administer oral activated charcoal in acute overdose, even if presentation is
delayed. Give repeat doses at 4-h intervals.