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Diclofenac (Voltaren)

Analgesicprescriptionoral · inferred

Phenylacetic acid NSAID, one of the most potent and widely used NSAIDs worldwide. Moderate COX-2 selectivity (between traditional NSAIDs and coxibs). Available in numerous formulations: oral (immediate/enteric/extended-release), topical gel (1%), transdermal patch, ophthalmic, and IM injection. Extensive first-pass metabolism (50% bioavailability). Short half-life but prolonged synovial fluid residence. CYP2C9 substrate.

Projected serum levels — 50 mg, once daily

Diclofenac (Voltaren)
Diclofenac (Voltaren) modeled serum levels, 50 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 50 mg once daily (oral).

Modeled steady state after ~1 days: peak ≈ 12.5 mg, trough ≈ 0.012 mg body load. Population-based estimate over 15 days for a 50 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Analgesic
Route modeled
Oral
Model confidence
inferred
Half-life
2 h
Common dose
50 mg
Suggested maximum
150 mg/day
Reference dose range
25–150 mg (single dose)
Suggested cadence
once daily
Validated against
50 mg oral — Cmax 1.5 mg/L at 2 h

Documented interactions

  • danger
    Carbamazepine (Tegretol) + Diclofenac (Voltaren) CYP induction

    Carbamazepine (Tegretol) inducer of CYP2C9 predicted to change Diclofenac (Voltaren) AUC by ~0.50x

  • danger
    Levothyroxine (Synthroid) + Diclofenac (Voltaren) Protein binding

    Diclofenac (Voltaren) may displace Levothyroxine (Synthroid) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free…

  • danger
    Phenobarbital + Diclofenac (Voltaren) CYP induction

    Phenobarbital inducer of CYP2C9 predicted to change Diclofenac (Voltaren) AUC by ~0.50x

  • danger
    Rifampin + Diclofenac (Voltaren) CYP induction

    Rifampin inducer of CYP2C9 predicted to change Diclofenac (Voltaren) AUC by ~0.43x

  • warning
    Apigenin + Diclofenac (Voltaren) Protein binding

    Apigenin may displace Diclofenac (Voltaren) from plasma protein binding sites, transiently raising free drug concentration.

  • warning
    Aripiprazole (Abilify) + Diclofenac (Voltaren) Protein binding

    Aripiprazole (Abilify) may displace Diclofenac (Voltaren) from plasma protein binding sites, transiently raising free drug concentration.

Serum checks 190 modeled interaction pairings for diclofenac (voltaren) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Efficacy and safety of topical diclofenac sodium gel for hand osteoarthritis: a randomized controlled trial Altman RD et al. · Journal of Rheumatology, 2009 DOI

    RCT demonstrating topical diclofenac gel significantly reduces hand OA pain with minimal systemic absorption (<5% of oral levels), supporting its role as a safer alternative to oral NSAIDs.

  2. Clinical pharmacokinetics of diclofenac: therapeutic insights and pitfalls Willis JV et al. · Clinical Pharmacokinetics, 1979 DOI

    PK study establishing diclofenac half-life of 1-2 hours despite prolonged clinical effect (due to tissue retention), 50% oral bioavailability from first-pass metabolism, and extensive CYP2C9/UGT conjugation.

2 published studies referenced in the app, each with a plain-language summary.