Assay of aspirin and naproxen analgesia

Single dose oral aspirin for acute postoperative pain in adults

BACKGROUND

This review is an update of a previously published review in the Cochrane Database of Systematic Reviews on 'Single dose oral aspirin for acute pain'. Aspirin has been known for many years to be an effective analgesic for many different pain conditions. Although its use as an analgesic is now limited in developed countries, it is widely available, inexpensive, and remains commonly used throughout the world.

OBJECTIVES

To assess the analgesic efficacy and associated adverse events of single dose oral aspirin in acute postoperative pain.

SEARCH METHODS

For the earlier review, we identified randomised trials by searching CENTRAL (The Cochrane Library) (1998, Issue 1), MEDLINE (1966 to March 1998), EMBASE (1980 to January 1998), and the Oxford Pain Relief Database (1950 to 1994). We updated searches of CENTRAL, MEDLINE, and EMBASE to January 2012.

SELECTION CRITERIA

Single oral dose, randomised, double-blind, placebo-controlled trials of aspirin for relief of established moderate to severe postoperative pain in adults.

DATA COLLECTION AND ANALYSIS

We assessed studies for methodological quality and two review authors extracted the data independently. We used summed total pain relief (TOTPAR) over four to six hours to calculate the number of participants achieving at least 50% pain relief. We used these derived results to calculate, with 95% confidence intervals, the relative benefit compared to placebo, and the number needed to treat (NNT) for one participant to experience at least 50% pain relief over four to six hours. We sought numbers of participants using rescue medication over specified time periods, and time to use of rescue medication, as additional measures of efficacy. We collected information on adverse events and withdrawals.

MAIN RESULTS

We included 68 studies in which aspirin was used at doses from 300 mg to 1200 mg, but the vast majority of participants received either 600/650 mg (2409 participants, 64 studies) or 990/1000 mg (380 participants, eight studies). There was only one new study.Studies were overwhelmingly of adequate or good methodological quality. NNTs for at least 50% pain relief over four to six hours were 4.2 (3.9 to 4.8), 3.8 (3.0 to 5.1), and 2.7 (2.0 to 3.8) for 600/650 mg, 900/1000 mg, and 1200 mg respectively, compared with placebo. Type of pain model had no significant impact on the results. Lower doses were not significantly different from placebo. These results do not differ from those of the earlier review.Fewer participants required rescue medication with aspirin than with placebo over four to eight hours postdose, but by 12 hours there was no difference. The number of participants experiencing adverse events was not significantly different from placebo for 600/650 mg aspirin, but for 900/1000 mg the number needed to treat to harm was 7.5 (4.8 to 17). The most commonly reported events were dizziness, drowsiness, gastric irritation, nausea, and vomiting, nearly all of which were of mild to moderate severity.

AUTHORS' CONCLUSIONS

Aspirin is an effective analgesic for acute pain of moderate to severe intensity. High doses are more effective, but are associated with increased adverse events, including drowsiness and gastric irritation. The pain relief achieved with aspirin was very similar milligram for milligram to that seen with paracetamol. There was no change to the conclusions in this update.

Single dose oral naproxen and naproxen sodium for acute postoperative pain in adults

BACKGROUND

Naproxen, a non-steroidal anti-inflammatory drug, is used to treat various painful conditions including postoperative pain, and is often administered as the sodium salt to improve its solubility. This review updates a 2004 Cochrane review showing that naproxen sodium 550 mg (equivalent to naproxen 500 mg) was effective for treating postoperative pain. New studies have since been published.

OBJECTIVES

To assess efficacy, duration of action, and associated adverse events of single dose oral naproxen or naproxen sodium in acute postoperative pain in adults.

SEARCH STRATEGY

We searched Cochrane CENTRAL, MEDLINE, EMBASE and the Oxford Pain Relief Database for studies to October 2008.

SELECTION CRITERIA

Randomised, double blind, placebo-controlled trials of single dose orally administered naproxen or naproxen sodium in adults with moderate to severe acute postoperative pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. Pain relief or pain intensity data were extracted and converted into the dichotomous outcome of number of participants with at least 50% pain relief over four to six hours, from which relative risk and number-needed-to-treat-to-benefit (NNT) were calculated. Numbers of participants using rescue medication over specified time periods, and time to use of rescue medication, were sought as additional measures of efficacy. Information on adverse events and withdrawals were collected.

MAIN RESULTS

The original review included 10 studies with 996 participants. This updated review included 15 studies (1509 participants); 11 assessed naproxen sodium and four naproxen. In nine studies (784 participants) using 500/550 mg naproxen or naproxen sodium the NNT for at least 50% pain relief over four to six hours was 2.7 (95% CI 2.3 to 3.2). No dose response was demonstrated over the range 200/220 mg to 500/550 mg, but limited data was identified. Median time to use of rescue medication was 8.9 hours for naproxen 500/550 mg and 2.0 hours for placebo. Use of rescue medication was significantly less common with naproxen than placebo. Associated adverse events were generally of mild to moderate severity and rarely led to withdrawal.

AUTHORS' CONCLUSIONS

Doses equivalent to 500 mg and 400 mg naproxen administered orally provided effective analgesia to adults with moderate to severe acute postoperative pain. About half of participants treated with these doses experienced clinically useful levels of pain relief, compared to 15% with placebo, and half required additional medication within nine hours, compared to two hours with placebo. Associated adverse events did not differ from placebo.

Dose-response in direct comparisons of different doses of aspirin, ibuprofen and paracetamol (acetaminophen) in analgesic studies

AIMS

Establishing the dose-response relationship for clinically useful doses of aspirin, ibuprofen and paracetamol has been difficult. Indirect comparison from meta-analysis is compromised by too little information at some doses.

METHODS

A systematic review of randomized, double-blind trials in acute pain comparing different doses of aspirin, ibuprofen and paracetamol was therefore undertaken.

RESULTS

Fifty trials were found. Numerical superiority of higher over lower dose was found by the original authors in 37/50 trials (74%) and statistical superiority in 11/50 (22%). Twenty-eight trials had design, quality and data reporting characteristics to allow pooling of common doses; in 3/28 (11%) of the individual trials our calculations showed statistical superiority of higher over lower dose. Pooled comparison of 1000/1200 mg aspirin over 500/600 mg was statistically superior, with a number-needed-to-treat (NNT) for higher over lower dose of 16 (8 to > 100). Pooled comparison of 400 mg ibuprofen over 200 mg was statistically superior, with an NNT for higher over lower dose of 10 (6-23). Pooled comparison of 1000 mg paracetamol over 500 mg was statistically superior, with an NNT for higher over lower dose of 9 (6-20).

CONCLUSIONS

Use of trials making direct comparison of two different doses of target drugs revealed the underlying dose-response curve for clinical analgesia.

Single dose oral naproxen and naproxen sodium for acute postoperative pain

BACKGROUND

Postoperative pain is often poorly managed. Treatment options include a range of drug therapies such as non-steroidal anti-inflammatory drugs (NSAIDs) of which naproxen is one. Naproxen is used to treat a variety of painful conditions including acute postoperative pain, and is often combined with sodium to improve its solubility for oral administration. Naproxen sodium 550 mg (equivalent to 500 mg of naproxen) is considered to be an effective dose for treating postoperative pain but to date no systematic review of the effectiveness of naproxen/naproxen sodium at different doses has been published.

OBJECTIVES

To assess the efficacy, safety and duration of action of a single oral dose of naproxen or naproxen sodium for acute postoperative pain in adults.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE and the Oxford Pain Relief Database for relevant studies. Additional studies were identified from the reference list of retrieved reports. The most recent search was undertaken in July 2004.

SELECTION CRITERIA

Included studies were randomised, double blind, placebo-controlled trials of a single dose of orally administered naproxen or naproxen sodium in adults with moderate to severe acute postoperative pain.

DATA COLLECTION AND ANALYSIS

Pain relief or pain intensity data were extracted and converted into dichotomous information to give the number of patients with at least 50% pain relief over four to six hours. Relative risk estimates (RR) and the number-needed-to-treat (NNT) for at least 50% pain relief were then calculated. Information was sought on the percentage of patients experiencing any adverse event, and the number-needed-to-harm was derived. Time to remedication was also estimated.

MAIN RESULTS

Ten trials (996 patients) met the inclusion criteria: nine assessed naproxen sodium; one combined the results from two small trials of naproxen alone. Included studies scored well for methodological quality. Meta-analysis of six trials (500 patients) that compared naproxen sodium 550 mg with placebo gave a RR for at least 50% pain relief over 4 to 6 hours of 4.2 (95% confidence interval (CI) 2.9 to 6.0) and an NNT of 2.6 (95% CI 2.2 to 3.2). Three trials (334 patients) assessed naproxen 400 mg and naproxen sodium 440 mg, giving a RR of 4.8 (95% CI 2.75 to 8.38). Two small studies indicated that naproxen 200 mg and naproxen sodium 220 mg may provide effective postoperative pain relief. There was no significant difference between the number of patients experiencing any adverse event on treatment compared with placebo. Weighted mean time to remedication for naproxen sodium 550 mg was 7.6 hours compared with 2.6 hours for placebo.

REVIEWERS' CONCLUSIONS

Naproxen sodium 550 mg, naproxen 400 mg and naproxen sodium 440 mg administered orally are effective analgesics for the treatment of acute postoperative pain in adults. A low incidence of adverse events was found but reporting was not consistent.

Single-dose oral naproxen for acute postoperative pain: a quantitative systematic review

BACKGROUND: Naproxen and naproxen sodium are non-steroidal anti-inflammatory drugs used in a variety of painful conditions, including the treatment of postoperative pain. This review aims to assess the efficacy, safety and duration of action of a single oral dose of naproxen/naproxen sodium for moderate to severe acute postoperative pain in adults, compared with placebo. METHODS: The Cochrane Library (issue 4 2002), EMBASE, PubMed, MEDLINE and an in-house database were searched for randomised, double blind, placebo controlled trials of a single dose of orally administered naproxen or naproxen sodium in adults with acute postoperative pain. Pain relief or pain intensity data were extracted and converted into dichotomous information to give the number of patients with at least 50% pain relief over 4 to 6 hours. Relative benefit and number-needed-to-treat were then calculated. The percentage of patients with any adverse event, number-needed-to-harm, and time to remedication were also calculated. RESULTS: Ten trials with 996 patients in met the inclusion criteria. Six trials compared naproxen sodium 550 mg (252 patients) with placebo (248 patients); the NNT for at least 50% pain relief over six hours was 2.6 (95% confidence interval 2.2 to 3.2). There was no significant difference between the number of patients experiencing any adverse event on treatment compared with placebo. Weighted mean time to remedication was 7.6 hours for naproxen sodium 550 mg (206 patients) and 2.6 hours for placebo (205 patients). Four other trials used lower doses. CONCLUSION: A single oral dose of naproxen sodium 550 mg is an effective analgesic in the treatment of acute postoperative pain. A low incidence of adverse events was found, although these were not reported consistently.

Single dose oral aspirin for acute pain

BACKGROUND

Aspirin has been known to be an effective analgesic for many years and is commonly used throughout the world for many different pain conditions. It is important for both prescribers and patients to have the best possible information about the efficacy and safety of analgesics, and this need is reflected in patient surveys which show that postoperative pain is often poorly managed. We also need to benchmark relative efficacy and safety of current analgesics so that we can compare them with new analgesics.

OBJECTIVES

To quantitatively assess the analgesic efficacy and adverse effects of a single-dose of aspirin in acute pain of moderate to severe intensity.

SEARCH STRATEGY

Randomised trials were identified by searching Medline (1966 to March 1998), Embase (1980 to January 1998), the Cochrane Library (Issue 1,1998) and the Oxford Pain Relief Database (1950 to 1994).

SELECTION CRITERIA

The inclusion criteria used were: full journal publication, postoperative pain or a mixture of postoperative and acute trauma pain, oral administration, adult patients, baseline pain of moderate to severe intensity, double-blind design, and random allocation to treatment groups which compared aspirin with placebo.

DATA COLLECTION AND ANALYSIS

Summed pain relief or pain intensity difference over four to six hours was extracted, and converted into dichotomous information yielding the number of patients with at least 50% pain relief. This was then used to calculate the relative benefit and the number-needed-to-treat (NNT) for one patient to achieve at least 50% pain relief.

MAIN RESULTS

Seventy-two randomised single-dose trials met our inclusion criteria, with 3253 patients given aspirin, and 3297 placebo. Significant benefit of aspirin over placebo was shown for aspirin 600/650 mg, 1000 mg and 1200 mg, NNTs for at least 50% pain relief of 4.4 (4.0 to 4.9), 4.0 (3.2 to 5.4) and 2.4 (1.9 to 3.2) respectively. Single-dose aspirin 600/650 mg produced significantly more drowsiness and gastric irritation than placebo, with a number-needed-to-harm (NNH) of 28 (19 to 52) and 38 (22 to 174) respectively. Type of pain model, pain measurement, sample size, quality of study design, and study duration had no significant impact on the results.

REVIEWER'S CONCLUSIONS

Aspirin is an effective analgesic for acute pain of moderate to severe intensity with a clear dose-response. Drowsiness and gastric irritation were seen as significant adverse effects even though the studies were single-dose. The pain relief achieved with aspirin was very similar milligram for milligram to that seen with paracetamol.

Pain relief following herniotomy: a double-blind randomized comparison between naproxen and placebo

Sixty consecutive out-patients were randomly assigned to have either a non-steroid anti-inflammatory drug (naproxen 500 mg) or an identical placebo administered as suppositories half an hour before unilateral herniotomy. Within 1.5 h after the end of surgery, pain scores were significantly improved in patients receiving naproxen (P less than 0.02). The long-term analgesic effect was measured indirectly by registering the postoperative requirement for supplementary analgesic doses of acetylsalicylic acid 1 g plus codeine 20 mg. The time elapsing before the first demand for additional analgesics was prolonged by median 1.5 h, and the need for further analgesic treatment during 24 h was significantly reduced (P less than 0.003) in the naproxen group (median, 2 doses) compared to the placebo group (median, 4 doses). No statistically significant difference was found between the groups with regard to the occurrence of side-effects.

Relief of pain and trismus in patients treated with naproxen or acetylsalicylic acid after tonsillectomy

The pain-relieving efficacy of naproxen and acetylsalicylic acid (ASA) in tonsillectomized patients was compared in a double blind parallel clinical trial comprising 83 patients, among whom 42 were treated with naproxen and 41 with ASA. The patients were treated post-operatively for two days with either naproxen suppositories 500 mg. twice, or ASA effervescent tablets 1000 mg. three times, daily. The therapeutic gain was evaluated by recording the intensity of pain, reduced ability to open the mouth (trismus), consumption of supplementary analgesic (parcetamol), and pain-related sleep disturbances. The statistical analysis of the results revealed no differences in pain intensity, consumption of additional analgesics or pain-related sleep disturbances in the two treatment groups. A considerable degree of trismus was demonstrated in most of the tonsillectomized patients. This reduced ability to open the mouth was gradually overcome in the naproxen group while it remained unchanged in the ASA group, however, no statistical significant difference could be demonstrated. Additionally, no significant positive correlation between pain intensity and trismus was proven. The pain-relieving effect, however, was unsatisfactory in both the naproxen and the ASA group, and clinical controlled trial studies of alternative analgetics in tonsillectomized patients are still to be encouraged.

Analgesic regimens for third molar surgery: pharmacologic and behavioral considerations

The level of pain following the extraction of impacted third molars was evaluated in 75 patients. Participants were administered acetaminophen 1,000 mg or a placebo before surgery. After surgery, acetaminophen 650 mg was administered either at fixed intervals or as needed to relieve pain. When acetaminophen was administered before surgery, the onset of peak pain was delayed and patient discomfort was decreased 3, 4, and 5 hours after surgery. Patients following the fixed interval regimen after surgery experienced more pain overall and requested the backup narcotic analgesic more frequently. Of the regimens tested, patients preferred the regimen of acetaminophen 1,000 mg administered before surgery with acetaminophen administered as needed for pain after surgery.

A double-blind, randomized study of naproxen and acetylsalicylic acid after surgical removal of impacted lower third molars

100 patients had an impacted lower 3rd molar surgically removed in a double-blind study. Naproxen (500 mg b.i.d.) or acetylsalicylic acid (ASA) (1 g t.i.d.) were administered to the patients. Paracetamol was allowed as escape medication. 49 patients received naproxen and 51 ASA. 4 patients from each group were excluded because they took other analgesics, took too few tablets, were lost to follow-up or had misunderstood the instructions. There was a significantly better over all analgesic effect of naproxen than ASA (p = 0.004). More patients in the naproxen group than in the ASA group (p less than 0.01) would accept treatment with the same drug again. 4 patients, all from the ASA group, complained spontaneously about side effects.

Human pharmacokinetics of analgesics and methods for their determination in biological fluids

The main pharmacokinetic data of analgesics--biological half-lives, apparent volumes of distribution, total body clearances--obtained in humans, and their clinical relevance are summarized. Special emphasis has been given to the analytical methods used for the quantitative determination of these drugs in biological fluids.

Bioavailability of naproxen sodium and its relationship to clinical analgesic effects

1 In the first of a series of trials with naproxen sodium it was shown that patients achieved significantly earlier and higher plasma levels of naproxen when naproxen sodium was administered. 2 In a second study comparing naproxen with naproxen sodium in patients with post-partum pain, pain intensity was consistently lower for the group receiving naproxen sodium. However, statistically significant differences were not seen until 4 to 5 h after medication. 3 A final study documented that a more frequent dosage schedule of every 6 h led to clearly higher plasma levels than those achieved with an every 8 h regimen; plasma levels did not plateau. Doses up to 1,375 mg/day were well tolerated. 4 In conclusion, naproxen sodium appears to be an improved form of naproxen for use as a analgesic agent.

Comparative analgesic effects of naproxen sodium, aspirin, and placebo

The analgesic efficacy of a single 550-mg dose of naproxen sodium was compared with that of 650 mg aspirin and a placebo in a double-blind, parallel trial. The study was carried out in an industrial setting and included 201 adult patients with various acute pain states. Musculoskeletal pain was the most common type of pain treated. Pain intensity differences and patients' evaluation of pain relief indicated statistically significantly earlier and better analgesia with naproxen sodium than with both aspirin and placebo. The summed pain intensity differences (SPID) showed that naproxen sodium performed better than aspirin, which in turn did better than placebo. the difference between naproxen sodium and aspirin means for SPID was numerically equal to the difference between the aspirin and placebo means for SPID. Further, the incidence of side effects was less with naproxen sodium than with aspirin. The study demonstrated that naproxen sodium provided earlier and better pain relief than aspirin, that this effect was consistent over time, and that the incidence of side effects associated with naproxen sodium was less than with aspirin.