NSAID toxicity

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Mefenamic acid has important consequences in overdosage because it can cause convulsions

About

• Commonly available and may be seen in overdose
• Occasionally patients may take excess to manage pain
• Commonest are Ibuprofen and Mefenamic acid (Ponstan) often used for menstrual pain.

Clinical

• Gastric irritation and mild abdominal pain.
• Mefenamic acid can famously cause seizures
• Overdose may also cause acute kidney injury and Metabolic acidosis
• Reduced GCS and drowsiness, nystagmus and tachycardia are rarely seen.

Investigations

• Monitor U&E, LFTs and FBC.

Management

• If reduced GCS place in the recovery position. Manage ABCs.
• Give activated charcoal 50 g if more than 10 tablets in the past 1-2 hours
• Manage ongoing seizures with IV/PR Diazepam and follow the usual treatment regimen. A single self-terminating seizure is managed conservatively managed
• Oral PPI e.g. Omeprazole may be given if there have been significant dyspeptic GI symptoms and manage any Upper GI haemorrhage as per usual protocol
• Most patients are medically fit for discharge by 12 hours if stable and no evidence of complication
• Psychiatric evaluation in all overdoses.

Do not prescribe nonsteroidal anti-inflammatory drugs (NSAIDs) to people with:

• Active gastrointestinal (GI) bleeding, or active GI ulcer or a history of GI bleeding related to previous NSAID therapy, or a history of GI perforation related to previous NSAID therapy or a history of recurrent GI haemorrhage (two or more distinct episodes), or history of recurrent GI ulceration (two or more distinct episodes).
• A history of hypersensitivity/severe allergic reaction to an NSAID (including Aspirin) for example, asthma, rhinitis, angioedema or urticaria.
• Severe heart failure.
• Severe hepatic impairment serum albumin less than 25 g/l or Child-Pugh score of 10 or more.
• Severe renal impairment eGFR less than 30 mL/minute/1.73 m2.

Do not prescribe COX-2 inhibitors, diclofenac, aceclofenac or high dose ibuprofen (more than 2400 mg daily) to people with:

• Ischaemic heart disease. Inflammatory bowel disease (COX-2 inhibitors only).
• Peripheral arterial disease or Cerebrovascular disease.
• CHF (New York Heart Association [NYHA] classification II-IV).
• Avoid etoricoxib or high dose ibuprofen to people with BP persistently above 140/90 mmHg

Prescribe NSAIDs with caution to people with:

• A history of peptic ulceration (standard NSAIDs are contraindicated), or people at high risk of GI adverse effects (for example, the elderly).
• Allergic disorders, Cardiac impairment, or heart failure as NSAIDs may impair renal function.
• Cerebrovascular disease, Coagulation disorders, Connective-tissue disorders.
• Hypertension as NSAIDs may impair renal function.
• Inflammatory bowel disease NSAIDs may increase the risk of developing or cause exacerbations of ulcerative colitis or Crohn's disease.
• Ischaemic heart disease or Peripheral arterial disease.
• Risk factors for cardiovascular events, for example, hypertension, hyperlipidaemia, diabetes mellitus, smoking.
• Hepatic impairment dose reductions may be necessary.
• Renal impairment (avoid if possible) sodium and water retention may occur leading to a deterioration in renal function and, possibly renal failure.
• If the person cannot avoid using an NSAID and has impaired renal function, monitor creatinine clearance or eGFR.

Also prescribe NSAIDs with caution in:

• Women trying to conceive NSAIDs may impair female fertility. The elderly increased risk of cardiovascular, renal, and serious GI adverse effects (including GI bleeding and perforation, which may be fatal).