The assessment and treatment of theophylline poisoning

Theophylline Toxicity: A Differential to Consider in Patients on Long-Term Theophylline Presenting With Nonspecific Symptoms

Theophylline has been used for decades as a bronchodilator to treat asthma and chronic obstructive pulmonary disease (COPD). The precise mode of action is still uncertain. Since beta-2 agonists are at least as effective as theophylline as a bronchodilator while having fewer side effects, theophylline has become less popular in recent clinical practice as the first-line treatment in patients with airway obstruction due to its narrow therapeutic window, which necessitates frequent level monitoring, severe side effects that can be fatal, and interactions with other medications. Patients with a chronic theophylline overdose often present with nonspecific gastrointestinal symptoms, which can result in misdiagnosis for a variety of gastrointestinal conditions. Convulsions that may be fatal can occur as a result of a theophylline overdose. Therefore, it is important to manage individuals who have been taking theophylline for a long period and have nonspecific cardiac or gastrointestinal symptoms with a high index of suspicion for theophylline toxicity. We present a case of a COPD patient who had no regular theophylline level monitoring for two years. He presented with vague gastrointestinal symptoms for the past six months and was initially suspected of having gastrointestinal cancer due to weight loss caused by decreased oral intake due to nausea and vomiting. He was suspected of having theophylline toxicity because he was on long-term theophylline and did not have frequent theophylline level monitoring. His theophylline level was measured and found to be high at 28.9 mL/L (normal level, 15 mL/L). He was given conservative treatment, including intravenous fluid and electrolyte replacements, and close monitoring of his theophylline levels.

Therapeutic drug monitoring in drug overdose

The treatment of poisoned patients is still largely defined by history, clinical assessment and interpretation of ancillary investigations. Measurement of drug concentrations is clinically important for relatively few compounds. Most measurements form an adjunct to and should not be considered a substitute for clinical assessment. Drug concentrations are particularly important for those compounds where the concentration is predictive of serious toxicity in an otherwise asymptomatic patient.

Haemodynamic study as guideline for the use of beta blockers in acute theophylline poisoning

It has been proposed that beta-blocker therapy reverses metabolic and cardiovascular disorders in acute theophylline poisoning. We present a case of acute theophylline overdose treated with esmolol under haemodynamic control. Haemodynamic monitoring was useful in determining the appropriate duration of administration of esmolol and in deciding on treatment with fluids.

Salivary theophylline concentrations in neonates

Salivary theophylline concentrations in neonates were measured by a homogeneous enzyme immunoassay and compared with serum concentrations. Free serum theophylline concentrations were also compared with salivary concentrations and the values obtained were almost identical. Results using the immunoassay agreed well with those obtained using a high-performance liquid chromatographic procedure (HPLC).

Theophylline Toxicokinetics

Toxicokinetics, the application of pharmacokinetic principles in the assessment and management of the poisoned patient, is demonstrated for theophylline poisonings. Theophylline intoxication and its treatment is briefly reviewed and differentiated for acute or chronic etiologies. A toxicokinetic strategy for the simple calculation and evaluation of serum theophylline concentrations following sustained-release products overdosage is presented. A toxicokinetic basis for treatment durations of activated charcoal, hemoperfusion, or hemodialysis is described. Common toxicokinetic factors responsible for presentation with chronic theophylline intoxication are mentioned.

Effect of acute versus chronic intoxication on clinical features of theophylline poisoning in children

OBJECTIVES

To determine whether the method of intoxication influences the metabolic disturbances and pattern of life-threatening events that occur after theophylline intoxication in children.

METHODS

Five-year prospective observational study of consecutive pediatric patients referred to a regional poison control center with a theophylline concentration (theo) greater than or equal to 30 micrograms/ml. At the time of referral, intoxication was categorized as acute (single toxic exposure), chronic (long-term toxic exposure), or acute-on-therapeutic (single toxic exposure superimposed on maintenance therapy).

RESULTS

One-hundred twenty-five patients were monitored. Mean age was 12 years (range, 3 days to 20 y). Seventy-four patients (59%) had acute intoxication, 31 (25%) had chronic intoxication, and 20 (16%) had acute-on-therapeutic intoxication. Mean peak serum (theo) was 55 micrograms/ml. Life-threatening events occurred in 12 patients (10%). Patients with acute intoxication had a significantly lower serum potassium level (3.04 vs 3.80 mmol/L; p less than 0.001) and higher serum glucose level (10.8 vs 7.0 mmol/L (194 vs 127 mg/dl); p less than 0.001) than did children with chronic intoxication. Although life-threatening events (seizures or arrhythmias) occurred at a similar rate across categories, the (theo) at which these events occurred was significantly higher in patients with acute intoxication than in those with chronic intoxication (100 vs 42 micrograms/ml; p = 0.02). Among children with chronic intoxication, those who had life-threatening events had (theo) similar to those who remained well (42 vs 47 micrograms/ml) but were significantly younger (1.6 vs 8.0 years; p less than 0.001).

CONCLUSIONS

These data indicate that method of intoxication has significant effects on the metabolic and clinical consequences of theophylline poisoning. Life-threatening events occur in those with acute theophylline intoxication at significantly higher (theo) than in those with chronic intoxication. After chronic intoxication, peak (theo) does not identify patients at risk for life-threatening events; young age appears to be the primary risk factor. These findings potentially complicate the management of theophylline poisoning, given the difficulty of extracorporeal drug removal in young infants.

Management of theophylline overdose patients in the intensive care unit

In a retrospective survey of all adults admitted to the Intensive Care Unit with acute theophylline poisoning over the last five years, we identified 38 patients (6.8% of all admissions for poisoning), two of whom died. Thirty-five (92%) had taken a sustained-release preparation. Eight patients had grand mal seizures and six developed arrhythmias (ventricular fibrillation, 3; atrial fibrillation, 2; supraventricular tachycardia, 1). Severe vomiting was present in 34 (89%) and proved to be a serious obstacle to the administration of enteral charcoal. The vomiting was controlled by intravenous metoclopramide in seventeen patients (50%), but the remaining seventeen required mechanical ventilation with sedation and muscle relaxation for the effective delivery of nasogastric charcoal. Importantly, in nine (24%), the serum theophylline concentration continued to rise despite enteral charcoal. Charcoal haemoperfusion was used in seven (18%). We present an algorithm for the management of severe, acute theophylline poisoning.

Severe lactic acidosis following theophylline overdose

The patient with theophylline overdose commonly presents with gastrointestinal, cardiovascular, neurologic, and electrolyte abnormalities. Respiratory alkalosis is the most common acid-base alteration, but mild metabolic acidosis has been reported. Two cases of severe lactic acidosis (pH 6.67 and 6.63) in patients without hypoxemia, shock, or prolonged seizure activity are reported. Possible causative mechanisms and aspects of therapy are discussed. Theophylline toxicity should be considered when an unconscious patient with concurrent severe metabolic acidosis presents to the emergency department.

Acute theophylline intoxication

We describe a case of intentional acute theophylline intoxication with cardiac, cerebral, and gastrointestinal features of moderate-to-severe toxicity. The unusual metabolic and hematologic sequelae included hypokalemia, hyperglycemia, metabolic acidosis, extreme neutrophilia, increased creatinine levels attributed to muscle damage, and hematuria. The implications of these unusual findings for the management of acute theophylline intoxication include the recognition that these effects can be due to intoxication per se and do not necessarily indicate a primary endocrine disorder or infection.