Naproxen
Properties
| State | Solid (white to off-white crystalline powder) |
| Color | White to off-white |
| Solubility | Practically insoluble in water (15.9 mg/L at 25°C); soluble in ethanol and DMSO |
| Melting Point | 155-156°C |
| Boiling Point | Decomposes before boiling |
About Naproxen
Naproxen (C14H14O3, 230.259 g/mol) is the propionic-acid NSAID that anchors the over-the-counter pain category in the US under the brand name Aleve, and it is one of the earliest examples of a pharmaceutical sold as a single enantiomer. Syntex synthesized and patented the drug in 1976 with a then-novel asymmetric route that delivered the pure (S)-(+) form, exploiting the fact that the (R) enantiomer is essentially inactive against COX-1 and COX-2 and was associated with hepatotoxicity in early animal studies. Mechanistically, naproxen is a non-selective cyclooxygenase inhibitor — it blocks both isoforms with comparable potency, suppressing prostaglandin synthesis from arachidonic acid and thereby reducing inflammation, fever, and pain transmission. The defining clinical advantage versus ibuprofen is the half-life: 12 to 17 hours in plasma, which permits 12-hour dosing intervals (typically 220 mg q12h OTC, 500 mg q12h prescription) instead of the every-4-to-6-hour regimen ibuprofen requires. The longer exposure does come with trade-offs — chronic naproxen use carries the same NSAID-class GI ulceration and renal risks as other non-selective COX inhibitors. The cardiovascular profile is the bright spot: large meta-analyses have consistently placed naproxen at the lower end of NSAID CV risk, possibly because sustained COX-1 inhibition mimics low-dose aspirin's anti-platelet effect.
Where you'll encounter it
If you've ever taken Aleve for a sprained ankle or a tension headache, you've taken 220 mg of naproxen sodium — the salt form because it dissolves and absorbs faster than the free acid. Pharmacy techs see naproxen in two main contexts: the OTC blue-and-white tablets and the prescription 500 mg generics that rheumatologists hand out for osteoarthritis flares. In the medicinal chemistry lab, the compound is one of the standard teaching examples for chiral resolution because the historical Syntex route, the modern asymmetric hydrogenation, and the lipase-mediated kinetic resolution all give different ee values that students can compare by chiral HPLC. Anyone who has worked emergency medicine has also seen the downside — long-term naproxen users showing up with melena from a NSAID-induced gastric bleed, particularly elderly patients on it for chronic arthritis pain.
Common Uses
- Over-the-counter analgesic for headache, dental pain, and menstrual cramps
- Prescription anti-inflammatory for osteoarthritis and rheumatoid arthritis flares
- Acute gout treatment at 750 mg loading then 250 mg q8h until resolved
- Antipyretic for adult fever (preferred over aspirin in dengue-endemic regions)
- Tendinitis and bursitis pain management in sports medicine clinics
- Teaching example for asymmetric synthesis and chiral HPLC resolution
- Reference standard for non-selective COX-1/COX-2 inhibition in pharmacology assays
Safety Information
GHS Health Hazard classification (chronic toxicity). Common adverse effects: dyspepsia (10-20% of users), nausea, headache, mild fluid retention. Serious risks with chronic use: GI ulceration and bleeding (NNH around 100 over 6 months), renal impairment from sustained prostaglandin suppression, and elevated blood pressure. Contraindicated in active GI bleed, severe renal impairment (CrCl < 30 mL/min), late-pregnancy (third-trimester premature ductus closure), and within 14 days of CABG surgery. The FDA boxed warning covers cardiovascular thrombotic events and GI bleeding for the entire NSAID class, though naproxen sits at the lower CV-risk end. Do not co-administer with other NSAIDs. Standard adult OTC dose: 220 mg q8-12h, max 660 mg/day; prescription max 1000-1500 mg/day.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.