Can an adult with severe pain and previous paracetamol (acetaminophen) use take 400mg of ibuprofen?

Can You Take 400mg of Ibuprofen?

Yes, 400mg of ibuprofen is a safe and effective standard dose for adults with severe pain, and can be taken every 4-6 hours as needed, with a maximum daily dose of 2400mg (or up to 3200mg under physician supervision for chronic conditions). 1, 2

Standard Dosing Guidelines

For acute moderate to severe pain, ibuprofen 400mg every 4-6 hours is the recommended starting dose, with the FDA-approved maximum daily dose of 3200mg, though most guidelines recommend not exceeding 2400mg daily for safety. 1, 2 The 400mg dose has been shown to provide optimal pain relief—doses higher than 400mg in single administration do not provide significantly better analgesia. 2, 3

Combining with Paracetamol (Acetaminophen)

Since you've already taken paracetamol, combining ibuprofen 400mg with paracetamol 500-1000mg provides superior pain relief compared to either drug alone, with a Number Needed to Treat (NNT) of 1.5, meaning 2 out of 3 patients will achieve at least 50% pain relief. 4, 5 This combination:

• Provides better analgesia than ibuprofen 400mg alone (NNT 5.4 for the combination to outperform ibuprofen monotherapy) 5
• Extends time to needing rescue medication (median 8.3 hours vs 1.7 hours for placebo) 5
• Reduces adverse events compared to placebo 5

The combination is safe when paracetamol is kept below 4g daily and ibuprofen below 2400mg daily. 6

Duration of Use

For acute pain, limit ibuprofen to 5-10 days maximum. 1 If pain persists beyond 2 weeks, mandatory monitoring every 3 months is required, including blood pressure, kidney function (BUN/creatinine), liver function tests, complete blood count, and fecal occult blood testing. 1, 7

Critical Safety Considerations—When NOT to Take Ibuprofen

Absolute contraindications (do not take ibuprofen if you have): 1, 7

• Active peptic ulcer disease or history of gastrointestinal bleeding
• Severe heart failure
• Severe kidney disease (creatinine clearance significantly reduced)
• Aspirin-induced asthma
• Currently taking anticoagulants like warfarin (increases bleeding risk 5-6 times) 6

High-risk situations requiring extreme caution (consult physician first): 1, 7

• Age over 60 years (increased risk of all adverse effects)
• History of peptic ulcer disease (5% risk of recurrent bleeding within 6 months)
• Concurrent use of corticosteroids or SSRIs
• Hypertension (ibuprofen raises blood pressure by mean 5 mmHg) 7
• Significant alcohol consumption
• Dehydration or compromised fluid status

Mandatory Discontinuation Criteria

Stop ibuprofen immediately and seek medical attention if: 1, 7

• Black/tarry stools or vomiting blood (gastrointestinal bleeding)
• Decreased urine output, rising creatinine, or fluid retention (acute kidney injury)
• Blood pressure increases or worsens
• Worsening asthma symptoms
• BUN or creatinine doubles from baseline 6

Monitoring Requirements for Extended Use

If you need ibuprofen beyond 2 weeks, baseline and repeat testing every 3 months must include: 6, 1

• Blood pressure
• BUN and creatinine (kidney function)
• Liver function tests (alkaline phosphatase, LDH, SGOT, SGPT)
• Complete blood count
• Fecal occult blood

Practical Dosing Algorithm

For your situation (severe pain, previous paracetamol use):

1. Take ibuprofen 400mg now (can be taken with food/milk if stomach upset occurs) 2
2. Continue paracetamol 500-1000mg every 6 hours (maximum 4g daily) 6
3. Repeat ibuprofen 400mg every 4-6 hours as needed (maximum 2400mg daily for routine use) 1, 2
4. Do not exceed 10 days without physician reassessment 1
5. If inadequate relief after 2 doses, consider increasing single dose to 600-800mg, though evidence shows minimal additional benefit 3

Common Pitfalls to Avoid

• Hidden NSAIDs in combination medications: Check all medications to avoid duplicate NSAID exposure 7
• Timing with aspirin: If taking low-dose aspirin for heart protection, take ibuprofen at least 30 minutes AFTER immediate-release aspirin or at least 8 hours BEFORE aspirin to avoid blocking aspirin's cardioprotective effect 7
• Exceeding paracetamol limits: When combining with ibuprofen, carefully track total daily paracetamol from all sources (including combination products) to stay under 4g daily 6