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Mechanism Of Action

Ibuprofen's mechanism of action, like that of other NSAIDs, is not completely understood but may be related to prostaglandin synthetase inhibition. Caldolor possesses antiinflammatory, analgesic, and antipyretic activity.


Ibuprofen is a racemic mixture of [-]R- and [+]S-isomers. In vivo and in vitro studies indicate that the [+]S-isomer is responsible for clinical activity. The [-]R-form, while thought to be pharmacologically inactive, is slowly and incompletely (~60%) interconverted into the active [+]S species in adults. The [-]R-isomer serves as a circulating reservoir to maintain levels of active drug. The pharmacokinetic parameters of Caldolor determined in a study with volunteers are presented below.

Table 3: Pharmacokinetic Parameters of Intravenous Ibuprofen

  400 mg* Caldolor Mean (CV%) 800 mg* Caldolor Mean (CV%)
Number of Patients 12 12
AUC (mcg-h/mL) 109.3 (26.4) 192.8 (18.5)
Cmax (mcg/mL) 39.2 (15.5) 72.6 (13.2)
KEL (1/h) 0.32 (17.9) 0.29 (12.8)
T½ (h) 2.22 (20.1) 2.44 (12.9)
AUC = Area-under-the-curve
Cmax = Peak plasma concentration
CV = Coefficient of Variation
KEL = First-order elimination rate constant
T½ = Elimination half-life
* = 60 minute infusion time

Ibuprofen, like most NSAIDs, is highly protein bound ( > 99% bound at 20 mcg/mL). Protein binding is saturable, and at concentrations > 20 mcg/mL binding is nonlinear. Based on oral dosing data, there is an age- or fever-related change in volume of distribution for ibuprofen.

Clinical Studies

Analgesia (Pain)

The effect of Caldolor on acute pain was evaluated in two multi-center, randomized, double-blind, placebo-controlled studies.

In a study of women who had undergone an elective abdominal hysterectomy, 319 patients were randomized and treated with Caldolor 800 mg or placebo administered every 6 hours (started intra-operatively) and morphine administered on an as needed basis. Efficacy was demonstrated as a statistically significant greater reduction in the mean morphine consumption through 24 hours in patients who received Caldolor as compared to those receiving placebo (47 mg and 56 mg, respectively). The clinical relevance of this finding is supported by a greater reduction in pain intensity over 24 hours for patients treated with Caldolor, even though morphine was available on an as needed basis.

In a study of patients who had undergone an elective abdominal or orthopedic surgery, 406 patients (87 men, 319 women) were randomized to receive Caldolor 400 mg, Caldolor 800 mg, or placebo administered every 6 hours (started intraoperatively), and morphine on an as needed basis. This study failed to demonstrate a statistically significant difference in outcome between patients receiving Caldolor 800 mg or 400 mg and placebo, although there were trends favoring the active treatments.

Antipyretic (Fever)

The effect of Caldolor on fever was evaluated in two randomized, double-blind studies.

In a multi-center study, 120 hospitalized patients (88 men, 32 women) with temperatures of 101°F or greater were randomized to Caldolor 400 mg, 200 mg, 100 mg or placebo, administered every 4 hours for 24 hours. Each of the three Caldolor doses, 100 mg, 200 mg, and 400 mg, resulted in a statistically greater percentage of patients with a reduced temperature ( < 101°F) after 4 hours, compared to placebo (65%, 73%, 77% and 32%, respectively). The dose response is shown in the figure below.

Figure 1: Temperature Reduction by Treatment Group, Hospitalized Febrile Patients

Temperature Reduction by Treatment Group, Hospitalized Febrile Patients - Illustration

In a single-center study, 60 hospitalized patients (48 men, 12 women) with uncomplicated P. falciparum malaria having temperatures ≥ 100.4°F were randomized to Caldolor 400 mg or placebo, administered every 6 hours for 72 hours of treatment. There was a significant reduction in fever within the first 24 hours of treatment, measured as the area above the temperature 98.6°F vs. time curve for patients treated with Caldolor.

Last reviewed on RxList: 1/29/2014
This monograph has been modified to include the generic and brand name in many instances.

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