Diclofenac sodium is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain, inflammation, and stiffness caused by conditions like arthritis. It belongs to the same broad family as ibuprofen and naproxen but is generally considered more potent, which is why most oral forms require a prescription. You’ll find it sold under brand names like Voltaren, though a lower-strength topical gel is available over the counter in many countries.
How Diclofenac Sodium Works
Your body produces chemicals called prostaglandins whenever tissue is injured or inflamed. Prostaglandins amplify pain signals, trigger swelling, and raise local temperature. Diclofenac blocks the two enzymes responsible for making prostaglandins, COX-1 and COX-2, with roughly equal strength. By cutting prostaglandin production at the source, it reduces pain, swelling, and stiffness relatively quickly.
What sets diclofenac apart from simpler NSAIDs is that it appears to work through several additional pathways. It influences how the body handles arachidonic acid (a fatty acid central to inflammation), interacts with pain-signaling receptors in the nervous system, and may alter the production of certain immune-signaling molecules. These extra mechanisms help explain why diclofenac is effective across a wide range of painful conditions, not just classic joint inflammation.
What It’s Used For
Diclofenac sodium is approved to treat osteoarthritis, rheumatoid arthritis, and a spinal condition called ankylosing spondylitis. For these chronic conditions, it helps manage daily pain and stiffness so people can stay mobile. It’s also prescribed for acute pain situations like menstrual cramps, dental pain, musculoskeletal injuries, and post-surgical discomfort.
The over-the-counter topical gel (1% strength) is specifically marketed for arthritis pain in joints close to the skin’s surface: hands, wrists, elbows, feet, ankles, and knees. Applying the gel directly over a painful joint delivers the drug locally while limiting how much enters the bloodstream.
Available Forms
Diclofenac comes in several formulations, each designed for different situations. Oral delayed-release (enteric-coated) tablets dissolve in the intestine rather than the stomach, which can reduce stomach irritation. Extended-release tablets deliver the drug slowly over a longer period, allowing once-daily dosing for chronic conditions. There are also topical gels, patches, and liquid-filled capsules.
You may also see “diclofenac potassium” on labels. The potassium salt dissolves and absorbs faster than the sodium salt, so it’s typically chosen when quick pain relief matters, like for acute headaches or menstrual cramps. Diclofenac sodium, with its slightly slower absorption, is more commonly used for ongoing conditions where steady, sustained relief is the goal. Both deliver the same active molecule once absorbed.
How Quickly It Works
For oral delayed-release tablets, blood levels of the drug peak at around 2.3 hours after a dose. The drug is then cleared relatively fast, with a half-life of about 2.3 hours, meaning half of it leaves your system in that time. Because the body processes it quickly, most oral forms are taken two or three times a day to maintain relief.
The topical gel works more slowly. You apply it four times daily to the affected joint, and it builds up in the local tissue over several days of consistent use. Pain relief from the gel tends to be more gradual compared to the oral tablets.
Topical Gel Dosing
The OTC 1% gel comes with a dosing card to help you measure the right amount. For upper body joints like hands, wrists, or elbows, you squeeze out a line of gel about 2.25 inches long per area. For lower body joints like knees, ankles, or feet, the line should be about 4.5 inches. You apply it four times a day, rubbing it gently into the skin over the joint. Avoid covering the area with tight bandages, and wash your hands after application unless you’re treating the hands themselves.
Cardiovascular and GI Risks
Like all NSAIDs, diclofenac sodium carries serious risks that increase with higher doses and longer use. The most significant are cardiovascular and gastrointestinal.
People taking NSAIDs have a higher risk of heart attack and stroke compared to those who don’t. This risk can appear within the first weeks of treatment and tends to climb the longer you take the drug. It applies even to people without pre-existing heart disease, though those who already have cardiovascular risk factors face a higher overall chance of a serious event. Diclofenac is contraindicated right before or after coronary artery bypass graft (CABG) surgery, because clinical trials found a clear increase in heart attacks and strokes during the 10 to 14 days following that procedure.
On the gastrointestinal side, NSAIDs can cause ulcers, bleeding, or perforations anywhere along the digestive tract. These events can happen at any point during treatment and sometimes strike without any warning symptoms. Older adults, people with a history of stomach ulcers, and heavy alcohol drinkers are at greatest risk. Warning signs to watch for include stomach pain, heartburn, vomiting material that looks bloody or like coffee grounds, and dark or tarry stools.
Pregnancy Safety
The FDA warns against using any NSAID, including diclofenac, at 20 weeks of pregnancy or later. Starting around that point, the drug can impair the developing baby’s kidney function, leading to dangerously low levels of amniotic fluid. In some reported cases, this drop in fluid occurred within 48 hours of starting the medication, though it more commonly develops over days to weeks. Low amniotic fluid can cause serious complications including restricted limb development and delayed lung maturation.
The kidney effects are often reversible once the drug is stopped, but in severe cases, newborns have needed intensive treatment. After 30 weeks of pregnancy, NSAIDs should be avoided entirely. Before 20 weeks, the risk appears much lower, but short-term use at the lowest effective dose is still the standard guidance.
Who Should Avoid It
Beyond pregnancy and CABG surgery, diclofenac sodium isn’t appropriate for everyone. People with active stomach ulcers or a history of serious GI bleeding should steer clear. Those with significant kidney disease or severe liver problems face higher risks of complications because the body relies on both organs to process and eliminate the drug. If you’ve ever had an allergic reaction to aspirin or another NSAID, such as hives, facial swelling, or asthma-like breathing trouble, diclofenac can trigger the same response.
People who have recently had a heart attack are also advised to avoid it unless specifically directed otherwise by a physician, since observational data from large national registries show an increased risk of repeat heart events, cardiovascular death, and overall mortality in this group starting in the first week of NSAID use.