About

Incorrect NSAID dosing accounts for a significant share of OTC medication adverse events reported to the FDA each year. Naproxen sodium (C₁₄H₁₃NaO₃, marketed as Aleve) delivers 220 mg per tablet with a plasma half-life of 12 - 17 hours, making overdose accumulation a real risk over multi-day use. This calculator applies FDA OTC labeling rules: a maximum of 660 mg per 24 hours for adults under 65, reduced to 440 mg for older adults due to elevated gastrointestinal and renal risk. It flags contraindicated drug combinations and known risk factors that standard label text buries in fine print.

The tool approximates OTC dosing guidance only. It does not replace physician consultation for prescription-strength naproxen (250 - 500 mg tablets), pediatric dosing (requires weight-based calculation by a clinician), or patients with hepatic impairment. Duration limits are enforced: 10 days for pain, 3 days for fever, per manufacturer labeling.

Formulas

OTC Aleve dosing follows a stepwise ceiling model. The total daily dose D_total must not exceed the population-specific maximum D_max:

D_total = D_initial + n∑i=1 D_subsequent,i ≤ D_max

where D_initial is the first dose (220 or 440 mg), each D_subsequent = 220 mg, and n is the number of follow-up doses within 24 hours.

D_max = {

660 mg if age < 65440 mg if age ≥ 65 or risk factors present

The minimum dosing interval t_min = 8 hours for standard adults, extended to 12 hours for elderly or renally impaired patients. Pediatric prescription dosing (not OTC) uses:

D_ped = W × 5 - 7 mg/kg

where W = body weight in kg, D_ped = single dose in mg, administered q8-12 h. This requires physician supervision and is not calculated for OTC self-medication.

Reference Data

Population	Single Dose	Interval	Max / 24 h	Max Duration (OTC)	Key Restriction
Adult 18-64	220 - 440 mg	q8-12 h	660 mg (3 tablets)	10 days pain / 3 days fever	Take with food or milk
Adult ≥ 65	220 mg	q12 h	440 mg (2 tablets)	10 days pain / 3 days fever	Higher GI bleed risk; consult physician
Child 12-17	220 mg	q8-12 h	660 mg	10 days pain / 3 days fever	Must be ≥ 12 years for OTC
Child < 12	Not recommended OTC - physician must calculate				Rx only; weight-based dosing
Pregnancy (1st - 2nd trimester)	220 mg	q12 h	440 mg	Shortest possible	Consult OB/GYN; risk Category C
Pregnancy (3rd trimester)	CONTRAINDICATED				Premature ductus closure risk
Renal impairment (mild)	220 mg	q12 h	440 mg	5 days max	Monitor creatinine; hydrate
Renal impairment (mod - severe)	AVOID - consult nephrologist				GFR < 30 contraindicates NSAIDs
Hepatic impairment	AVOID or use lowest dose				Naproxen is hepatically metabolized
History of GI ulcer / bleed	220 mg	q12 h	440 mg	3 - 5 days	Co-prescribe PPI if physician approves
On anticoagulants (warfarin)	AVOID - high bleed risk				INR potentiation; use acetaminophen
On SSRIs	220 mg	q12 h	440 mg	5 days	2 - 4× increased GI bleed risk
On ACE inhibitors / ARBs	220 mg	q12 h	440 mg	5 days	Reduces antihypertensive effect; renal risk
On corticosteroids	220 mg	q12 h	440 mg	3 days	Synergistic GI ulceration risk
On lithium	AVOID or monitor lithium levels closely				NSAIDs raise serum lithium 15 - 30%
On methotrexate	AVOID on high-dose MTX days				Reduced renal MTX clearance
Alcohol (≥ 3 drinks/day)	AVOID all NSAIDs				GI hemorrhage risk per FDA black box
Post-CABG surgery	CONTRAINDICATED				FDA black box: CV thrombotic events

Frequently Asked Questions

Aging reduces renal clearance of naproxen (GFR declines ~1 mL/min/year after 40). The plasma half-life extends from ~14 hours to 18+ hours in elderly patients, increasing accumulation risk. Combined with age-related mucosal thinning, the gastrointestinal hemorrhage risk rises 4-5× compared to younger adults. The FDA OTC label therefore caps elderly dosing at 440 mg/24 h (2 tablets) versus 660 mg/24 h for younger adults.

Combining two NSAIDs (naproxen + ibuprofen) does not improve efficacy but roughly doubles GI ulceration risk. Low-dose aspirin (81 mg) for cardiovascular protection is a special case: naproxen can interfere with aspirin's antiplatelet effect if taken simultaneously. The FDA recommends taking aspirin at least 30 minutes before or 8 hours after naproxen. This calculator flags NSAID co-administration as a contraindication.

Naproxen inhibits prostaglandin-mediated renal vasodilation. In patients with GFR < 60 mL/min, this can precipitate acute kidney injury. For mild impairment (GFR 60-89), the calculator reduces max dose to 440 mg/24 h and caps duration at 5 days. For moderate-to-severe impairment (GFR < 30), NSAIDs are contraindicated entirely. Always ensure adequate hydration when using any NSAID.

The 10-day limit exists because chronic NSAID use increases cardiovascular thrombotic event risk (MI, stroke) in a dose- and duration-dependent manner - this carries an FDA black box warning. GI ulceration risk also rises significantly after 7-10 days. If pain persists beyond 10 days, the underlying condition requires medical diagnosis rather than continued OTC self-treatment.

The OTC label uses fixed dosing (220 mg/tablet) regardless of adult weight because naproxen has high oral bioavailability (~95%) and predictable pharmacokinetics in the 50-120 kg range. However, at extremes: adults under 50 kg may experience higher peak plasma concentrations and should use the minimum effective dose. Adults over 100 kg may have slightly lower tissue concentrations but should never exceed label maximums. This calculator adjusts risk assessment for weight extremes.

Both naproxen and ethanol independently damage gastric mucosa. Combined, they create synergistic erosion that can progress to hemorrhagic gastritis. The FDA mandates a warning for patients consuming ≥3 alcoholic drinks daily. Studies show a 6× increased risk of GI bleeding in heavy drinkers using NSAIDs. The calculator flags this as a hard contraindication.

Not exactly. Naproxen sodium (Aleve) is the sodium salt form with molecular weight 252.24 g/mol versus 230.26 g/mol for naproxen base. The 220 mg naproxen sodium tablet contains approximately 200 mg of naproxen equivalent. The sodium salt form is absorbed faster (Tmax ~1-2 h vs 2-4 h), providing quicker onset. Prescription naproxen (Naprosyn) uses the base form at 250/375/500 mg tablets. Do not interchange dosing numbers between the two forms.