Diclofenac Sodium (Page 5 of 8)


8.1 Pregnancy

Pregnancy Category C prior to 30 weeks gestation; Category D starting 30 weeks gestation

Risk Summary

Use of NSAIDs, including diclofenac sodium, during the third trimester of pregnancy increases the risk of premature closure of the fetal ductus arteriosus. Avoid use of NSAIDs, including diclofenac sodium, in pregnant women starting at 30 weeks of gestation (third trimester).

There are no adequate and well-controlled studies of diclofenac sodium in pregnant women. Human and animal studies indicate that diclofenac crosses the placenta. Data from observational studies regarding potential embryofetal risks of NSAID use in women in the first or second trimesters of pregnancy are inconclusive. In the general U.S. population, all clinically recognized pregnancies, regardless of drug exposure, have a background rate of 2-4% for major malformations, and 15-20% for pregnancy loss. In animal reproduction studies, no evidence of teratogenicity was observed in mice, rats, or rabbits given diclofenac during the period of organogenesis at doses up to approximately 5, 5, and 10 times, respectively, the maximum recommended topical dose of diclofenac sodium , despite the presence of maternal and fetal toxicity at these doses [see Data]. Based on animal data, prostaglandins have been shown to have an important role in endometrial vascular permeability, blastocyst implantation, and decidualization. In animal studies, administration of prostaglandin synthesis inhibitors such as diclofenac, resulted in increased pre- and post-implantation loss.

Clinical Considerations

Labor or Delivery

There are no studies on the effects of diclofenac sodium during labor or delivery. In animal studies, NSAIDS, including diclofenac, inhibit prostaglandin synthesis, cause delayed parturition, and increase the incidence of stillbirth.


Animal data

Reproductive and developmental studies in animals demonstrated that diclofenac sodium administration during organogenesis did not produce teratogenicity despite the induction of maternal toxicity and fetal toxicity in mice at oral doses up to 20 mg/kg/day (approximately 5 times the maximum recommended human dose (MRHD) of diclofenac sodium based on bioavailability and body surface area (BSA) comparison), and in rats and rabbits at oral doses up to 10 mg/kg/day (approximately 5 and 10 times the MRHD based on bioavailability and BSA comparison).

In a study in which pregnant rats were orally administered 2 or 4 mg/kg diclofenac (approximately 1 and 2 times the MRHD based on bioavailability and BSA comparison) from Gestation Day 15 through Lactation Day 21, significant maternal toxicity (peritonitis, mortality) was noted. These maternally toxic doses were associated with dystocia, prolonged gestation, reduced fetal weights and growth, and reduced fetal survival.

8.2 Lactation

Risk Summary

Based on available data, diclofenac may be present in human milk. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for CATAFLAM and any potential adverse effects on the breastfed infant from the CATAFLAM or from the underlying maternal condition.


One woman treated orally with a diclofenac salt, 150 mg/day, had a milk diclofenac level of 100 mcg/L, equivalent to an infant dose of about 0.03 mg/kg/day. Diclofenac was not detectable in breast milk in 12 women using diclofenac (after either 100 mg/day orally for 7 days or a single 50 mg intramuscular dose administered in the immediate postpartum period).

8.3 Females and Males of Reproductive Potential



Based on the mechanism of action, the use of prostaglandin-mediated NSAIDs, including diclofenac sodium, may delay or prevent rupture of ovarian follicles, which has been associated with reversible infertility in some women. Published animal studies have shown that administration of prostaglandin synthesis inhibitors has the potential to disrupt prostaglandin-mediated follicular rupture required for ovulation. Small studies in women treated with NSAIDs have also shown a reversible delay in ovulation. Consider withdrawal of NSAIDs, including diclofenac sodium, in women who have difficulties conceiving or who are undergoing investigation of infertility.


8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

8.5 Geriatric Use

Elderly patients, compared to younger patients, are at greater risk for NSAID-associated serious cardiovascular, gastrointestinal, and/or renal adverse reactions. If the anticipated benefit for the elderly patient outweighs these potential risks, start dosing at the low end of the dosing range, and monitor patients for adverse effects [see Warnings and Precautions (5.1, 5.2, 5.3, 5.6, 5.13)].

Of the total number of subjects treated with diclofenac sodium topical gel in clinical studies, 498 were 65 years of age and over. No overall differences in effectiveness or safety were observed between these subjects and younger subjects, but greater sensitivity to the effect of NSAIDs in some older individuals cannot be ruled out.

Diclofenac, as with any NSAID, is known to be substantially excreted by the kidney, and the risk of toxic reactions to diclofenac sodium may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken when using diclofenac sodium topical gel in the elderly, and it may be useful to monitor renal function.


Symptoms following acute NSAID overdosages have been typically limited to lethargy, drowsiness, nausea, vomiting, and epigastric pain, which have been generally reversible with supportive care. Gastrointestinal bleeding has occurred. Hypertension, acute renal failure, respiratory depression, and coma have occurred, but were rare [see Warnings and Precautions (5.1, 5.2, 5.4, 5.6)].

Manage patients with symptomatic and supportive care following an NSAID overdosage. There are no specific antidotes. Forced diuresis, alkalinization of urine, hemodialysis, or hemoperfusion may not be useful due to high protein binding.

For additional information about overdosage treatment, contact a poison control center (1-800-222-1222).


Diclofenac sodium is a nonsteroidal anti-inflammatory drug (NSAID) for topical use only. The chemical name is 2-[(2,6-dichlorophenyl) amino]benzene-acetic acid, monosodium salt. The molecular weight is 318.14. Its molecular formula is C14 H10 Cl2 NNaO2 , and it has the following chemical structure:


It contains the active ingredient, diclofenac sodium, USP in an opaque, white gel base. Diclofenac sodium, USP is a white to off-white, amorphous, crystalline powder. Diclofenac sodium is a benzeneacetic acid derivative.

The inactive ingredients in diclofenac sodium topical gel include: carbomer homopolymer Type C, cocoyl caprylocaprate, fragrance, isopropyl alcohol, mineral oil, polyoxyl 20 cetostearyl ether, propylene glycol, purified water, and strong ammonia solution.


12.1 Mechanism of Action

Diclofenac has analgesic, anti-inflammatory, and antipyretic properties.

The mechanism of action of diclofenac sodium, like that of other NSAIDs, is not completely understood but involves inhibition of cyclooxygenase (COX-1 and COX-2).

Diclofenac is a potent inhibitor of prostaglandin synthesis in vitro. Diclofenac concentrations reached during therapy have produced in vivo effects. Prostaglandins sensitize afferent nerves and potentiate the action of bradykinin in inducing pain in animal models. Prostaglandins are mediators of inflammation. Because diclofenac is an inhibitor of prostaglandin synthesis, its mode of action may be due to a decrease of prostaglandins in peripheral tissues.

12.3 Pharmacokinetics

The pharmacokinetics of diclofenac sodium were assessed in healthy volunteers following repeated applications during 7 days of diclofenac sodium topical gel to 1 knee (4 x 4 g per day) or to 2 knees and 2 hands (4 x 12 g per day) versus the recommended oral dose of diclofenac sodium for the treatment of osteoarthritis (3 x 50 mg per day). A summary of the pharmacokinetic parameters is presented in Table 2.

Table 3. Pharmacokinetic Parameters and Comparison of Diclofenac Sodium Topical Gel to Oral Diclofenac Sodium Tablets After Repeated Administration

Cmax = maximum plasma concentration, tmax =time of Cmax .

AUC0-24 =area under the concentration time curve.

SD=standard deviation. CI=confidence interval.

Treatment Cmax (ng/mL) Tmax (hr) AUC0-24 (ng●h/mL)
Mean ± SD Median Mean ± SD
% of Oral (CI) Range % of Oral (CI)
Diclofenac sodium topical gel 233 ± 128
4 x 4 g per day 15 ± 7.3 14 (0-24) 5.8%
(=160 mg diclofenac sodium per day) 0.6% (0.5-0.7) (5-6.7)
Diclofenac sodium topical gel 53.8 ± 32 10 (0-24) 807 ± 478
4 x 12 g per day 2.2% 19.7%
(=480 mg diclofenac sodium per day) (1.9-2.6) (17-22.8)
Diclofenac sodium tablets,
orally 3 x 50 mg per day 2270 ± 778 6.5 (1-14) 3890 ± 1710
(=150 mg diclofenac sodium per day) 100% 100%

Systemic exposure (area under the concentration-time curve) and maximum plasma concentrations of diclofenac are significantly lower with diclofenac sodium topical gel than with comparable oral treatment of diclofenac sodium.

Systemic exposure with recommended use of diclofenac sodium topical gel (4 x 4 g per day applied to 1 knee) is on average 17 times lower than with oral treatment. (Basis: treatment with diclofenac sodium topical gel of 1 knee, 4 times a day versus 50 mg, 3 times a day of oral diclofenac tablets.) The amount of diclofenac sodium that is systemically absorbed from diclofenac sodium topical gel is on average 6% of the systemic exposure from an oral form of diclofenac sodium.

The average peak plasma concentration with recommended use of diclofenac sodium topical gel (4 x 4 g per day applied to 1 knee) is 158 times lower than with the oral treatment.

The pharmacokinetics of diclofenac sodium topical gel has been tested under conditions of moderate heat (application of a heat patch for 15 minutes prior to gel application) and of moderate exercise (first gel application followed by a 20-minute treadmill exercise). No clinically relevant differences of systemic absorption and of tolerability were found between applications of diclofenac sodium topical gel (4 x 4 g per day on 1 knee) with and under the conditions tested. However, the pharmacokinetics of diclofenac sodium topical gel was not tested under the condition of heat application following gel application. Therefore, concurrent use of diclofenac sodium topical gel and heat is not recommended.

Drug Interaction Studies

Aspirin: When NSAIDs were administered with aspirin, the protein binding of NSAIDs were reduced, although the clearance of free NSAID was not altered. The clinical significance of this interaction is not known. See Table 2 for clinically significant drug interactions of NSAIDs with aspirin [see Drug Interactions (7) ].

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