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Toxicology – Methylxanthine Toxicity (Caffeine, Theophylline, Theobromine)
Source
Methylxanthines include compounds such as caffeine, theophylline (used in respiratory diseases), and theobromine (found in chocolate). These substances are present in beverages, medications, and certain foods.
Typical Presentation
Toxicity often results from overdose—intentional or accidental—and can present with both gastrointestinal and cardiovascular symptoms. Severe cases may rapidly progress to life-threatening complications.
Clinical Features
Early symptoms commonly include headache, nausea, vomiting (often persistent), abdominal discomfort, and diarrhea. As toxicity worsens, patients may develop:
Mechanism of Action
Methylxanthines exert multiple effects:
Management
Treatment is primarily supportive and may include:
Key Points
Source
Methylxanthines include compounds such as caffeine, theophylline (used in respiratory diseases), and theobromine (found in chocolate). These substances are present in beverages, medications, and certain foods.
Typical Presentation
Toxicity often results from overdose—intentional or accidental—and can present with both gastrointestinal and cardiovascular symptoms. Severe cases may rapidly progress to life-threatening complications.
Clinical Features
Early symptoms commonly include headache, nausea, vomiting (often persistent), abdominal discomfort, and diarrhea. As toxicity worsens, patients may develop:
- Rapid heart rate and breathing
- Low blood pressure with wide pulse pressure
- Tremors, agitation, and restlessness
- Seizures, including status epilepticus
- Cardiac arrhythmias (ranging from sinus tachycardia to ventricular fibrillation)
Mechanism of Action
Methylxanthines exert multiple effects:
- Block adenosine receptors (removing inhibitory CNS effects)
- Stimulate β-adrenergic activity, increasing heart rate and blood pressure
- Inhibit phosphodiesterase, leading to increased cAMP and intracellular calcium
Management
Treatment is primarily supportive and may include:
- IV fluids and vasopressors (e.g., norepinephrine or phenylephrine) for hypotension
- Benzodiazepines for seizures
- Management of arrhythmias (often with calcium channel blockers)
- Activated charcoal to reduce absorption
- Whole bowel irrigation for sustained-release ingestions
Key Points
- Severe toxicity can cause persistent vomiting, seizures, and dangerous arrhythmias.
- Theobromine is especially toxic to animals (e.g., dogs, rabbits).
- Dialysis is considered in life-threatening cases.
- Multidose activated charcoal may enhance elimination.
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