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|Drug Toxicity with Specific Antidotes
⚠️ Mefenamic acid overdose is important because it can trigger seizures.
💡 Always check local poisons guidance in suspected NSAID toxicity.
📖 About
- 💊 Mefenamic acid (Ponstan) is an NSAID commonly used for menstrual pain and sometimes taken in overdose alongside ibuprofen.
- 🌍 Readily available in households → accidental and deliberate ingestions are not uncommon.
🧠 Clinical Features
- 🤢 GI upset: gastric irritation, abdominal pain, nausea, vomiting, diarrhoea.
- ⚡ Neurological: seizures (distinctive for mefenamic acid compared with other NSAIDs). Reduced GCS, drowsiness, and nystagmus are less common.
- 🩺 Other risks: acute kidney injury, metabolic acidosis, tachycardia.
🔬 Investigations
- 🧪 FBC, U&E, LFTs.
- Monitor renal function and electrolytes closely.
💊 Management
- 🛑 ABCs: airway protection if GCS reduced; recovery position if unconscious but breathing.
- 🍵 Activated charcoal: 50 g if ≥10 tablets ingested within the past 1–2 h (and airway safe).
- ⚡ Seizures: IV or PR diazepam as per standard seizure protocol. Single, self-limiting seizures may need only conservative management.
- 🩹 GI protection: PPIs (e.g. omeprazole) if dyspeptic symptoms or evidence of upper GI bleeding. Manage GI haemorrhage as per standard protocols.
- ⏳ Observation: Most patients can be discharged after 12 h if stable, seizure-free, and with no metabolic/renal complications.
👥 Psychiatric assessment is essential for deliberate overdoses.
🚫 Do NOT prescribe NSAIDs in people with:
- Active or previous GI bleeding/ulceration, perforation, or recurrent haemorrhage.
- Severe allergic reaction to NSAIDs (e.g. aspirin-induced asthma, angioedema, urticaria).
- Severe cardiac failure, hepatic impairment (albumin <25 g/L or Child-Pugh ≥10), or renal impairment (eGFR <30).
⚠️ Avoid COX-2 inhibitors, diclofenac, or high-dose ibuprofen (>2400 mg daily) in:
- Ischaemic heart disease, peripheral arterial disease, cerebrovascular disease.
- NYHA class II–IV heart failure.
- Uncontrolled hypertension (BP >140/90 mmHg for etoricoxib/high-dose ibuprofen).
⚖️ Prescribe NSAIDs with caution in:
- Peptic ulcer history, elderly patients, or those at high risk of GI adverse effects (always add gastroprotection).
- Renal impairment (avoid if possible; monitor eGFR/Cr if essential).
- Cardiovascular disease, hypertension, diabetes, hyperlipidaemia, smokers (↑ CV risk).
- Allergic disorders or connective tissue disease (↑ risk of renal impairment).
- Women trying to conceive (NSAIDs may impair fertility).
