“Diclofenac diethylammonium”, commonly called diclofenac diethylamine, is a salt form of diclofenac used mainly in topical nonsteroidal anti-inflammatory drug (NSAID) preparations. It is formulated as gels, creams, emulsions, and sprays for local treatment of pain and inflammation involving muscles, tendons, ligaments, joints, and soft tissues.
The salt is especially suitable for topical delivery because it can be incorporated into hydroalcoholic or emulsion-based gels that spread over the skin. Products such as Voltaren Emulgel are applied directly to painful areas, potentially providing local diclofenac exposure with lower systemic concentrations than oral diclofenac. However, topical treatment does not eliminate NSAID risks, particularly when large areas are treated, skin is damaged, treatment is prolonged, or other NSAIDs are used simultaneously.
Chemical Structure
Diclofenac diethylammonium is the diethylamine salt of diclofenac. Its chemical name is 2-[2-(2,6-dichloroanilino)phenyl]acetic acid; N-ethylethanamine. It contains diclofenac in its anionic form paired with a diethylammonium cation.
The molecular formula is , and the molecular weight is approximately 369.29 g/mol. Common CAS numbers include 78213-16-8 and 156604-79-4, depending on the database and salt designation.
The molecule includes a phenylacetic acid structure, two chlorine atoms, an anilino linkage, and a diethylammonium counterion. The salt form differs from diclofenac sodium, diclofenac potassium, and diclofenac epolamine, although all release the active diclofenac moiety.
Diclofenac Diethylammonium-Based Medicines: Top Eight
Representative products include:
- Voltaren Emulgel 1.16%.
- Voltaren Emulgel Extra Strength 2.32%.
- Voltaren Emulgel Joint Pain.
- Voltaren Emulgel Back and Muscle Pain.
- Diclac Gel.
- Olfen Gel.
- Diclo-ratiopharm Gel.
- Generic diclofenac diethylamine gel, cream, or spray.
Brand names and strengths vary by country. A 1.16% diclofenac diethylamine gel commonly corresponds to approximately 1% diclofenac sodium-equivalent activity, while 2.32% products are marketed as extra-strength preparations. These products are not necessarily interchangeable without checking the label.
Mechanism of Action
Diclofenac Diethylammonium inhibits cyclooxygenase enzymes, particularly COX-2 and, to a lesser extent, COX-1. These enzymes convert arachidonic acid into prostaglandin precursors. Prostaglandins contribute to pain sensitization, swelling, redness, and inflammation.
By lowering prostaglandin synthesis at the application site, Diclofenac Diethylammonium reduces local pain and inflammatory symptoms. Topical administration may produce higher concentrations in skin, subcutaneous tissues, muscles, and joints near the application site than in the systemic circulation.
Diclofenac Diethylammonium does not directly repair damaged tendons, ligaments, cartilage, or muscles. It provides symptomatic relief while the underlying injury heals and should generally be combined with appropriate rest, physical measures, and medical evaluation when needed.
Pharmacokinetics
After topical application, diclofenac penetrates through the skin into local tissues. Systemic absorption is much lower than with oral diclofenac, although absorption depends on the area treated, dose, frequency, skin condition, occlusion, and duration.
Diclofenac Diethylammonium is more than 99% protein bound in plasma. It undergoes hepatic metabolism, mainly through CYP2C9, and metabolites are eliminated primarily in urine and bile. Topical formulations generally produce lower plasma exposure, but clinically relevant systemic effects remain possible.
Damaged or inflamed skin may increase absorption. Applying the product under tight or airtight dressings can also increase penetration and should not be done unless directed by a healthcare professional.
Therapeutic Uses
| Condition | Role of diclofenac diethylammonium | Typical use |
|---|---|---|
| Ankle or wrist sprain | Reduces local pain and inflammation | Applied to intact skin around the injured area |
| Muscle strain | Provides symptomatic relief | Used with rest and supportive care |
| Sports injuries | Helps reduce pain and swelling | Applied according to product directions |
| Bruising and contusions | Reduces local inflammatory discomfort | Short-term topical treatment |
| Tendinitis | Relieves pain around inflamed tendons | Medical evaluation may be required |
| Bursitis | Reduces localized pain | Used as an adjunct, not definitive therapy |
| Hand osteoarthritis | Provides local analgesia | Some products are approved for arthritis pain |
| Knee or other superficial-joint osteoarthritis | Reduces pain and stiffness | Use depends on product and national approval |
Health Canada product information lists relief of pain associated with acute localized muscle or joint injuries, including sprains, strains, and sports injuries. Some diclofenac topical products in other countries are also authorized for osteoarthritis and localized rheumatic conditions.
Side Effects
Common local reactions include dryness, redness, itching, burning, rash, scaling, irritation, and contact dermatitis. Photosensitivity reactions may occur, so treated skin should be protected from excessive sunlight or artificial ultraviolet exposure.
Although uncommon, systemic NSAID effects can occur. These may include stomach pain, indigestion, nausea, gastrointestinal bleeding, kidney impairment, fluid retention, elevated blood pressure, and worsening heart failure. Serious allergic reactions may cause wheezing, facial swelling, hives, or anaphylaxis.
Topical diclofenac may also cause severe blistering or exfoliative skin reactions. The medicine should be stopped and medical care obtained if a spreading rash, blistering, swelling, or breathing difficulty develops.
Drug Interactions
Systemic absorption from topical diclofenac is low, and formal interaction studies are limited. However, using it together with oral diclofenac, ibuprofen, naproxen, aspirin at anti-inflammatory doses, or another topical NSAID can increase the risk of adverse effects. Product information commonly advises against combining diclofenac diethylamine with other diclofenac products or oral NSAIDs without medical advice.
Potential systemic NSAID interactions include increased bleeding with anticoagulants and antiplatelet drugs, reduced antihypertensive effectiveness with ACE inhibitors or angiotensin-receptor blockers, reduced diuretic effect, and increased kidney injury risk with diuretics or nephrotoxic medicines.
Patients taking lithium, digoxin, methotrexate, cyclosporine, tacrolimus, corticosteroids, or selective serotonin-reuptake inhibitors should consult a clinician before prolonged or extensive use.
Safety Considerations
Diclofenac diethylammonium should be applied only to clean, intact skin. It should not be used on open wounds, infected skin, eczema, mucous membranes, or near the eyes. Hands should be washed after application unless the hands are being treated.
NSAIDs may increase the risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke. They may also cause gastrointestinal bleeding, ulceration, and perforation, even without warning symptoms. The risk is lower with topical therapy than oral therapy but is not completely absent.
The product should be used cautiously in people with cardiovascular disease, kidney or liver disease, hypertension, asthma triggered by aspirin or NSAIDs, stomach ulcers, or a history of gastrointestinal bleeding.
Diclofenac Diethylammonium should be avoided during the third trimester of pregnancy because NSAIDs may cause premature closure of the fetal ductus arteriosus. Pregnant or breastfeeding patients should seek professional advice before use.
Regulatory Status
Diclofenac diethylammonium gels and emulsions are authorized in many countries as topical NSAID medicines. Voltaren Emulgel products are marketed in multiple strengths, including 1.16% and 2.32%, for acute localized soft-tissue pain and, in certain jurisdictions, osteoarthritis.
In the United States, topical diclofenac products include diclofenac sodium gel and solution; diclofenac diethylamine is more commonly used in international products. Approval status, age limits, concentrations, and indications vary by country. Prescription and nonprescription classifications also differ.
Conclusion
Diclofenac diethylammonium is a topical diclofenac salt used to relieve localized pain and inflammation from sprains, strains, sports injuries, tendinitis, bursitis, bruises, and selected forms of osteoarthritis. It acts by inhibiting prostaglandin production through COX blockade and generally produces lower systemic exposure than oral diclofenac. Nevertheless, users should avoid damaged skin, duplicate NSAID therapy, excessive application, and late-pregnancy use, while seeking medical advice for persistent symptoms or serious reactions.
