What should be done for a patient who has ingested Midol (acetaminophen) by mistake?

Management of Accidental Midol (Acetaminophen) Ingestion

For a 30-year-old male who accidentally took Midol, blood testing is only necessary if he took a potentially hepatotoxic quantity (>7.5g) or has symptoms of toxicity; otherwise, reassurance is sufficient.

Assessment of Acetaminophen Exposure

First, determine the extent of the exposure:

1. Quantity assessment:

   • Ask specifically how many tablets/capsules were ingested
   • Standard Midol contains 500mg acetaminophen per tablet
   • Calculate total acetaminophen dose (number of tablets × 500mg)

2. Time since ingestion:

   • Determine exact time of ingestion if possible
   • This is critical for proper interpretation of acetaminophen levels

3. Risk threshold determination:

   • Hepatotoxicity risk begins at ingestion of ≥150 mg/kg (approximately 10.5g for a 70kg adult) 1
   • Medical evaluation recommended for single ingestions exceeding 7.5g 1

Decision Algorithm

Scenario 1: Low-risk ingestion

• If ingestion was less than 4g total (8 regular-strength tablets):
  • Reassurance that toxicity is extremely unlikely
  • No laboratory testing needed
  • Patient can be discharged with education

Scenario 2: Moderate to high-risk ingestion

• If ingestion was >7.5g OR unknown quantity with concerning symptoms:
  • Obtain serum acetaminophen level at least 4 hours post-ingestion 2, 3
  • Check liver function tests (AST, ALT), renal function, and coagulation studies
  • Use Rumack-Matthew nomogram to guide treatment if within 24 hours of ingestion 3

Scenario 3: Symptomatic patient

• If patient has nausea, vomiting, abdominal pain, or jaundice:
  • Obtain acetaminophen level regardless of reported dose
  • Check liver function tests, even if acetaminophen level is low

Laboratory Testing

If testing is indicated:

• Serum acetaminophen concentration (must be ≥4 hours post-ingestion for accurate risk assessment) 2
• Liver function tests (AST, ALT)
• Basic metabolic panel
• Coagulation studies (PT/INR)

Treatment Approach

When N-acetylcysteine (NAC) is indicated:

• Initiate NAC if:

  • Acetaminophen level plots above the "possible toxicity" line on the Rumack-Matthew nomogram (≥100 mg/L at 4 hours) 1
  • Patient presents >8 hours after significant ingestion (>7.5g) 2
  • Patient has elevated liver enzymes (AST or ALT >50 IU/L) with history of overdose 2

• NAC dosing regimen:

  • Total dose: 300 mg/kg given as 3 separate infusions over 21 hours 3
  • Loading dose: 150 mg/kg over 15-60 minutes
  • Second dose: 50 mg/kg over 4 hours
  • Third dose: 100 mg/kg over 16 hours 1, 3

Common Pitfalls to Avoid

1. Don't rely solely on patient's estimate of tablets ingested - histories concerning time and amount are often unreliable 4

2. Don't wait for laboratory results if >8 hours since significant ingestion - NAC is most effective when started within 8 hours 1

3. Don't dismiss case because patient is asymptomatic - hepatotoxicity develops 24-48 hours after ingestion, when the patient may initially appear well 5

4. Don't check acetaminophen levels too early - levels obtained less than 4 hours post-ingestion cannot be reliably interpreted with the nomogram 2, 3

5. Don't assume normal liver enzymes rule out toxicity - transaminase elevations typically peak 48-96 hours after ingestion 4

Special Considerations

• Monitor for hypersensitivity reactions to NAC (10-15% of patients) 1
• Consider risk factors that may increase susceptibility to acetaminophen toxicity:
  • Chronic alcohol use
  • Malnutrition
  • Use of enzyme-inducing medications 1, 5

In this specific case of a 30-year-old male who took Midol by mistake and is requesting blood testing, the approach should be guided by the quantity ingested and time since ingestion. If the ingestion was minimal (1-2 tablets), reassurance without testing is appropriate. If the quantity is concerning or unknown, proceed with acetaminophen level and liver function tests.