Which analgesic—intravenous paracetamol, intramuscular diclofenac, or intravenous tramadol (Acupan)—is most appropriate as first‑line treatment for abdominal pain, headache, chest pain, and back pain?

Analgesic Selection for Different Pain Presentations

For acute abdominal pain, headache, chest pain, and back pain presentations, intravenous paracetamol should be the first-line analgesic across all scenarios due to its superior safety profile, lack of gastrointestinal/renal/cardiovascular toxicity, and proven efficacy in acute pain management. 1, 2, 3

Specific Analgesic Matching by Pain Type

Abdominal Pain → IV Paracetamol (First Choice)

• Paracetamol 1 gram IV every 6 hours is the optimal choice for acute abdominal pain because it provides effective analgesia without the gastrointestinal bleeding risk, renal toxicity, or cardiovascular complications associated with NSAIDs like diclofenac. 1, 2, 3
• In emergency general surgery contexts, IV paracetamol in multimodal regimens demonstrates cost-effective pain control with shorter hospital stays and fewer complications compared to opioid-only approaches. 1
• Avoid IM diclofenac in abdominal pain due to concerns about anastomotic dehiscence, technical failures, and wound healing inhibition, particularly in emergency abdominal surgery patients. 1
• Tramadol (Acupan) should be reserved for moderate-to-severe pain inadequately controlled by paracetamol, not as first-line therapy. 1

Headache → IV Paracetamol (First Choice)

• Paracetamol provides effective relief for tension-type headache and mild-to-moderate migraine with minimal adverse effects. 4
• The evidence shows paracetamol at standard doses (1 gram IV every 6 hours) provides approximately 4 hours of effective analgesia for 36% of patients with acute pain. 5
• IM diclofenac may be considered for severe migraine, but paracetamol should be attempted first due to superior safety profile. 3, 4
• Tramadol offers no advantage over paracetamol for headache and carries higher risk of nausea, vomiting, and dizziness. 6

Chest Pain → IV Paracetamol (First Choice, with Critical Caveat)

• For musculoskeletal chest pain, IV paracetamol 1 gram every 6 hours is appropriate first-line therapy. 2, 3
• Critical safety consideration: Cardiac chest pain requires immediate cardiac workup and is NOT an analgesic selection scenario—this is a medical emergency requiring specific cardiac protocols. 2
• Avoid NSAIDs (diclofenac) in patients with known cardiovascular disease until cardiovascular safety investigations are complete, as NSAIDs carry increased cardiovascular risk. 1, 3
• Tramadol should not be first-line for chest pain due to delayed onset and opioid-related side effects. 1

Back Pain → IV Paracetamol or IM Diclofenac (Context-Dependent)

• For acute mechanical back pain without contraindications, IM diclofenac 50 mg (up to 4 times daily, maximum 200 mg/day) provides superior analgesia compared to paracetamol alone. 1, 4
• However, paracetamol remains first-line if the patient has gastrointestinal disease history, renal impairment (eGFR <60), cardiovascular disease, or is elderly (≥60 years). 2, 3
• The combination of paracetamol + diclofenac is more effective than either alone for back pain, but start with paracetamol monotherapy first. 1, 4
• Tramadol showed no efficacy difference compared to paracetamol + codeine in chronic back pain trials, offering no advantage. 6

Critical Safety Algorithm for NSAID (Diclofenac) Use

Diclofenac is CONTRAINDICATED if any of the following are present: 1, 2, 3

• Active peptic ulcer disease or GI bleeding history
• Renal insufficiency (eGFR <60 mL/min/1.73m²)
• Known cardiovascular disease or recent cardiac events
• Coagulopathy or concurrent anticoagulation
• Age ≥60 years (relative contraindication—use paracetamol instead)
• Emergency abdominal surgery context (anastomotic concerns)

Tramadol (Acupan) Positioning

Tramadol should NOT be first-line for any of these pain presentations because: 1, 6

• It offers no efficacy advantage over paracetamol in acute pain settings
• It carries significantly higher adverse effect burden (nausea 23%, vomiting, dizziness, constipation)
• It has more drug interaction potential than other options
• Guidelines consistently position tramadol as second-line for mild-to-moderate pain, reserved for inadequate response to non-opioid analgesics

Reserve tramadol for: 1

• Moderate-to-severe pain unresponsive to paracetamol ± NSAIDs
• Combination therapy with paracetamol when escalation is needed
• Situations requiring opioid analgesia but where strong opioids are not yet indicated

Practical Dosing Summary

IV Paracetamol: 1 gram every 6 hours (maximum 4 grams/24 hours in adults <60 years; maximum 3 grams/24 hours in elderly ≥60 years). 1, 2

IM Diclofenac: 50-75 mg every 8-12 hours (maximum 200 mg/24 hours), only if no contraindications present. 1

IV Tramadol (Acupan): 50-100 mg every 4-6 hours as needed (maximum 400 mg/24 hours), reserved for breakthrough pain. 1

Common Pitfall to Avoid

Do not assume NSAIDs are superior analgesics simply because they are anti-inflammatory. The evidence shows paracetamol provides comparable analgesia for most acute pain conditions with dramatically better safety profile, making it the rational first choice across nearly all presentations. 3, 5, 4 Only in specific musculoskeletal inflammatory conditions (like acute back pain in young, healthy patients) does diclofenac offer meaningful advantage. 4