Aspirin overdose:
Salicylate poisoning is usually associated with plasma concentrations >350 mg/L (2.5 mmol/L). Most adult deaths occur in patients whose concentrations exceed 700 mg/L (5.1 mmol/L). Single doses less than 100 mg/kg are unlikely to cause serious poisoning.
Symptoms:
Common features include vomiting, dehydration, tinnitus, vertigo, deafness, sweating, warm extremities with bounding pulses, increased respiratory rate and hyperventilation. Some degree of acid-base disturbance is present in most cases.
A mixed respiratory alkalosis and metabolic acidosis with normal or high arterial pH (normal or reduced hydrogen ion concentration) is usual in adults and children over the age of four years. In children aged four years or less, a dominant metabolic acidosis with low arterial pH (raised hydrogen ion concentration) is common.
Acidosis may increase salicylate transfer across the blood brain barrier.
Uncommon features include haematemesis, hyperpyrexia, hypoglycaemia, hypokalaemia, thrombocytopaenia, increased INR/PTR, intravascular coagulation, renal failure and non-cardiac pulmonary oedema.
Central nervous system features including confusion, disorientation, coma and convulsions are less common in adults than in children.
Management:
Give activated charcoal if an adult presents within one hour of ingestion of more than 250 mg/kg. The plasma salicylate concentration should be measured, although the severity of poisoning cannot be determined from this alone and the clinical and biochemical features must be taken into account.
Elimination is increased by urinary alkalinisation, which is achieved by the administration of 1.26% sodium bicarbonate. The urine pH should be monitored. Correct metabolic acidosis with intravenous 8.4% sodium bicarbonate (first check serum potassium). Forced diuresis should not be used alone since it does not enhance salicylate excretion and may cause pulmonary oedema.
Haemodialysis is the treatment of choice for severe poisoning and should be considered in patients with plasma salicylate concentrations >700 mg/L (5.1 mmol/L), or lower concentrations associated with severe clinical or metabolic features. Patients under 10 years or over 70 have increased risk of salicylate toxicity and may require dialysis at an earlier stage.
Caffeine overdose:
Symptoms: Common features include GI disturbance, epigastric pain, vomiting, diuresis, tachycardia or cardiac arrhythmia, “rambling†flow of thought and speech, psychomotor agitation, CNS stimulation (insomnia, restlessness, excitement, agitation, jitteriness, tremors and convulsions) or periods of inexhaustibility.
Management:
No specific antidote is available, but supportive measures such as beta adrenoceptor antagonists to reverse the cardiotoxic effects may be used.
Iron salts, phenobarbital sodium, hexamine, quinine salts, potassium and sodium iodides, free acids, alkali hydroxides, carbonates and stearates.
Adverse events from historical clinical trial data are both infrequent and from small patient exposure. Events reported from extensive post-marketing experience at therapeutic/labelled dose and considered attributable are tabulated below by MedDRA System Organ Class. Due to limited clinical trial data, the frequency of these adverse events is not known (cannot be estimated from available data).
Aspirin
| Body System | Undesirable effect |
| Gastrointestinal disorders | Nausea, vomiting, dyspepsia. Gastrointestinal ulceration, gastrointestinal haemorrhage and gastritis. |
| Renal and urinary disorders | Renal dysfunction, increased blood uric acid levels. |
| Hepatobiliary disorders | Elevation in aminotransferase levels. |
| Blood and lymphatic system disorders | Prolonged bleeding time. Thrombocytopenia. Ecchymosis |
| Metabolism and Nutrition disorders | Sodium and fluid retention. |
| Immune system disorders | Hypersensitivity reactions e.g. rhinitis, angioedema, urticaria, bronchospasm, skin reactions and anaphylaxis. |
| Respiratory, thoracic and mediastinal disorders | Bronchospasm in patients sensitive to aspirin and other NSAIDs |
| Ear and labyrinth disorders | Tinnitus, temporary hearing loss. |
Caffeine
| Body System | Undesirable effect |
| Central nervous system | Nervousness and dizziness. |
| When the recommended aspirin-caffeine dosing regimen is combined with dietary caffeine intake, the resulting higher dose of caffeine may increase the potential for caffeine- related adverse effects such as insomnia, restlessness, anxiety, irritability, headaches, gastrointestinal disturbances and palpitations. | |
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at:www.mhra.gov.uk/yellowcard.
None stated
Aspirin provides the analgesic and antipyretic actions required for the recommended indications.
Caffeine is a mild stimulant.
Aspirin is rapidly absorbed from the upper gastrointestinal tract after oral administration and is rapidly distributed throughout the whole body. It is hydrolysed to its active primary metabolite salicylic acid and completely excreted in the urine, principally as glucuronic acid and glycine conjugates of salicylic acid, but also as salicylic acid itself.
Salicylates are extensively bound to plasma proteins. Maximum plasma concentrations are reached after 10-40 minutes (acetylsalicylic acid) and 0.3 - 2 hours (total salicylate) depending on dosage form. The elimination half life of acetylsalicylic acid is dose-dependent, typically two hours after a single dose of 0.5 g aspirin, 4 hours after 1 gram and 20 hours after 5 grams.
Following administration of acetylsalicylic acid, salicylic acid can be detected in breast milk, cerebral spinal fluid and synovial fluid. The substance crosses the placenta.
None
Not applicable.
