A double-blind randomized study of an aspirin/caffeine combination versus acetaminophen/aspirin combination versus acetaminophen versus placebo in patients with moderate to severe post-partum pain

Genetics, pathophysiology, diagnosis, treatment, management, and prevention of migraine

Migraine is a neurological ailment that is characterized by severe throbbing unilateral headache and associated with nausea, photophobia, phonophobia and vomiting. A full and clear mechanism of the pathogenesis of migraine, though studied extensively, has not been established yet. The current available information indicates an intracranial network activation that culminates in the sensitization of the trigemino-vascular system, release of inflammatory markers, and initiation of meningeal-like inflammatory reaction that is sensed as headache. Genetic factors might play a significant role in deciding an individual's susceptibility to migraine. Twin studies have revealed that a single gene polymorphism can lead to migraine in individuals with a monogenic migraine disorder. In this review, we describe recent advancements in the genetics, pathophysiology, diagnosis, treatment, management, and prevention of migraine. We also discuss the potential roles of genetic and abnormal factors, including some of the metabolic triggering factors that result in migraine attacks. This review will help to accumulate current knowledge about migraine and understanding of its pathophysiology, and provides up-to-date prevention strategies.

Paracetamol/acetaminophen (single administration) for perineal pain in the early postpartum period

BACKGROUND

Perineal pain is a common but poorly studied adverse outcome following childbirth. Pain may result from perineal trauma due to bruising, spontaneous tears, surgical incisions (episiotomies), or in association with operative vaginal births (ventouse or forceps-assisted births). This is an update of a review last published in 2013.

OBJECTIVES

To determine the efficacy of a single administration of paracetamol (acetaminophen) used in the relief of acute postpartum perineal pain.

SEARCH METHODS

For this update, we searched the Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (9 December 2019), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs), including cluster-RCTs, comparing paracetamol to placebo. We excluded quasi-RCTs and cross-over trials. Data from abstracts would be included only if authors had confirmed in writing that the data to be included in the review had come from the final analysis and would not change.

DATA COLLECTION AND ANALYSIS

Two review authors assessed each study for inclusion and extracted data. One review author reviewed the decisions and confirmed calculations for pain relief scores. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

This update identified no new trials so the results remain unchanged. However, by applying the GRADE assessment of the evidence, the interpretation of main results differed from previous version of this review. We identified 10 studies involving 2044 women, but all these studies involved either three or four groups, looking at differing drugs or doses. We have only included the 1301 women who were in the paracetamol versus placebo arms of the studies. Of these, five studies (482 women) assessed 500 mg to 650 mg and six studies (797 women) assessed 1000 mg of paracetamol. One study assessed 650 mg and 1000 mg compared with placebo and contributed to both comparisons. We used a random-effects meta-analysis because of the clinical variability among studies. Studies were from the 1970s to the early 1990s, and there was insufficient information to assess the risk of bias adequately, hence the findings need to be interpreted within this context. The certainty of the evidence for the two primary outcomes on which data were available was assessed as low, downgraded for overall unclear risk of bias and for heterogeneity (I² statistic 60% or greater). More women may experience pain relief with paracetamol compared with placebo (average risk ratio (RR) 2.14, 95% confidence interval (CI) 1.59 to 2.89; 10 trials, 1279 women), and fewer women may need additional pain relief with paracetamol compared with placebo (average RR 0.34, 95% CI 0.21 to 0.55; 8 trials, 1132 women). However, the certainty of the evidence was low, downgraded for unclear overall risk of bias and substantial heterogeneity. One study used the higher dose of paracetamol (1000 mg) and reported maternal drug adverse effects. There may be little or no difference in the incidence of nausea (average RR 0.18, 95% CI 0.01 to 3.66; 1 trial, 232 women; low-certainty evidence), or sleepiness (average RR 0.89, 95% CI 0.18 to 4.30; 1 trial, 232 women; low-certainty evidence). No other maternal adverse events were reported. None of the studies assessed neonatal drug adverse effects.

AUTHORS' CONCLUSIONS

A single dose of paracetamol may improve perineal pain relief following vaginal birth, and may reduce the need for additional pain relief. Potential adverse effects for both women and neonates were not appropriately assessed. Any further trials should also address the gaps in evidence concerning maternal outcomes such as satisfaction with postnatal care, maternal functioning/well-being (emotional attachment, self-efficacy, competence, autonomy, confidence, self-care, coping skills) and neonatal drug adverse effects.

Relief of pain due to uterine cramping/involution after birth

BACKGROUND

Women may experience differing types of pain and discomfort following birth, including cramping pain (often called after-birth pain) associated with uterine involution, where the uterus contracts to reduce blood loss and return the uterus to its non-pregnant size. This is an update of a review first published in 2011.

OBJECTIVES

To assess the effectiveness and safety of pharmacological and non-pharmacological pain relief/analgesia for the relief of after-birth pains following vaginal birth.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (31 October 2019), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials comparing two different types of analgesia or analgesia versus placebo or analgesia versus no treatment, for the relief of after-birth pains following vaginal birth. Types of analgesia included pharmacological and non-pharmacological. Quasi-randomised trials were not eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, conducted 'Risk of bias' assessment, extracted data and assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

In this update, we include 28 studies (involving 2749 women). The evidence identified in this review comes from middle- to high-income countries. Generally the trials were at low risk of selection bias, performance bias and attrition bias, but some trials were at high risk of bias due to selective reporting and lack of blinding. Our GRADE certainty of evidence assessments ranged from moderate to very low certainty, with downgrading decisions based on study limitations, imprecision, and (for one comparison) indirectness. Most studies reported our primary outcome of adequate pain relief as reported by the women. No studies reported data relating to neonatal adverse events, duration of hospital stay, or breastfeeding rates. Almost half of the included studies (11/28) excluded breastfeeding women from participating, making the evidence less generalisable to a broader group of women. Non-steroidal anti-inflammatory drugs (NSAIDs) compared to placebo NSAIDs are probably better than placebo for adequate pain relief as reported by the women (risk ratio (RR) 1.66, 95% confidence interval (CI) 1.45 to 1.91; 11 studies, 946 women; moderate-certainty evidence). NSAIDs may reduce the need for additional pain relief compared to placebo (RR 0.15, 95% CI 0.07 to 0.33; 4 studies, 375 women; low-certainty evidence). There may be a similar risk of maternal adverse events (RR 1.05, 95% CI 0.78 to 1.41; 9 studies, 598 women; low-certainty evidence). NSAIDs compared to opioids NSAIDs are probably better than opioids for adequate pain relief as reported by the women (RR 1.33, 95% CI 1.13 to 1.57; 5 studies, 560 women; moderate-certainty evidence) and may reduce the risk of maternal adverse events (RR 0.62, 95% CI 0.43 to 0.89; 3 studies, 255 women; low-certainty evidence). NSAIDs may be better than opioids for the need for additional pain relief, but the wide CIs include the possibility that the two classes of drugs are similarly effective or that opioids are better (RR 0.37, 95% CI 0.12 to 1.12; 2 studies, 232 women; low-certainty evidence). Opioids compared to placebo Opioids may be better than placebo for adequate pain relief as reported by the women (RR 1.26, 95% CI 0.99 to 1.61; 5 studies, 299 women; low-certainty evidence). Opioids may reduce the need for additional pain relief compared to placebo (RR 0.48, 95% CI 0.28 to 0.82; 3 studies, 273 women; low-certainty evidence). Opioids may increase the risk of maternal adverse events compared with placebo, although the certainty of evidence is low (RR 1.59, 95% CI 0.99 to 2.55; 3 studies, 188 women; low-certainty evidence). Paracetamol compared to placebo Very low-certainty evidence means we are uncertain if paracetamol is better than placebo for adequate pain relief as reported by the women, the need for additional pain relief, or risk of maternal adverse events (2 studies, 123 women). Paracetamol compared to NSAIDs Very low-certainty evidence means we are uncertain if there are any differences between paracetamol and NSAIDs for adequate pain relief as reported by the women, or the risk of maternal adverse events. No data were reported about the need for additional pain relief comparing paracetamol and NSAIDs (2 studies, 112 women). NSAIDs compared to herbal analgesia We are uncertain if there are any differences between NSAIDs and herbal analgesia for adequate pain relief as reported by the women, the need for additional pain relief, or risk of maternal adverse events, because the certainty of evidence is very low (4 studies, 394 women). Transcutaneous nerve stimulation (TENS) compared to no TENS Very low-certainty evidence means we are uncertain if TENS is better than no TENS for adequate pain relief as reported by the women. No other data were reported comparing TENS with no TENS (1 study, 32 women).

AUTHORS' CONCLUSIONS

NSAIDs may be better than placebo and are probably better than opioids at relieving pain from uterine cramping/involution following vaginal birth. NSAIDs and paracetamol may be as effective as each other, whereas opioids may be more effective than placebo. Due to low-certainty evidence, we are uncertain about the effectiveness of other forms of pain relief. Future trials should recruit adequate numbers of women and ensure greater generalisability by including breastfeeding women. In addition, further research is required, including a survey of postpartum women to describe appropriately their experience of uterine cramping and involution. We identified nine ongoing studies, which may help to increase the level of certainty of the evidence around pain relief due to uterine cramping in future updates of this review.

Aspirin (single dose) for perineal pain in the early postpartum period

BACKGROUND

Perineal trauma, due to spontaneous tears, surgical incision (episiotomy), or in association with operative vaginal birth, is common after vaginal birth, and is often associated with postpartum perineal pain. Birth over an intact perineum may also lead to perineal pain. There are adverse health consequences associated with perineal pain for the women and their babies in the short- and long-term, and the pain may interfere with newborn care and the establishment of breastfeeding. Aspirin has been used in the management of postpartum perineal pain, and its effectiveness and safety should be assessed. This is an update of the review, last published in 2017.

OBJECTIVES

To determine the effects of a single dose of aspirin (acetylsalicylic acid), including at different doses, in the relief of acute postpartum perineal pain.

SEARCH METHODS

For this update, we searched the Cochrane Pregnancy and Childbirth's Trials Register (4 October 2019), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (4 October 2019) and screened reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs), assessing single dose aspirin compared with placebo, no treatment, a different dose of aspirin, or single dose paracetamol or acetaminophen, for women with perineal pain in the early postpartum period. We planned to include cluster-RCTs, but none were identified. We excluded quasi-RCTs and cross-over studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of the included RCTs. Data were checked for accuracy. The certainty of the evidence for the main comparison (aspirin versus placebo) was assessed using the GRADE approach.

MAIN RESULTS

We included 17 RCTs, 16 of which randomised 1132 women to aspirin or placebo; one RCT did not report numbers of women. Two RCTs (of 16) did not contribute data to meta-analyses. All women had perineal pain post-episiotomy, and were not breastfeeding. Studies were published between 1967 and 1997, and the risk of bias was often unclear, due to poor reporting. We included four comparisons: aspirin versus placebo (15 RCTs); 300 mg versus 600 mg aspirin (1 RCT); 600 mg versus 1200 mg aspirin (2 RCTs); and 300 mg versus 1200 mg aspirin (1 RCT). Aspirin versus placebo Aspirin may result in more women reporting adequate pain relief four to eight hours after administration compared with placebo (risk ratio (RR) 2.03, 95% confidence interval (CI) 1.69 to 2.42; 13 RCTs, 1001 women; low-certainty evidence). It is uncertain whether aspirin compared with placebo has an effect on the need for additional pain relief (RR 0.25, 95% CI 0.17 to 0.37; 10 RCTs, 744 women; very low-certainty evidence), or maternal adverse effects (RR 1.08, 95% CI 0.57 to 2.06; 14 RCTs, 1067 women; very low-certainty evidence), four to eight hours after administration. Analyses based on dose did not reveal any clear subgroup differences. 300 mg versus 600 mg aspirin It is uncertain whether over four hours after administration, 300 mg compared with 600 mg aspirin has an effect on adequate pain relief (RR 0.82, 95% CI 0.36 to 1.86; 1 RCT, 81 women) or the need for additional pain relief (RR 0.68, 95% CI 0.12 to 3.88; 1 RCT, 81 women). There were no maternal adverse effects in either aspirin group. 600 mg versus 1200 mg aspirin It is uncertain whether over four to eight hours after administration, 600 mg compared with 1200 mg aspirin has an effect on adequate pain relief (RR 0.85, 95% CI 0.52 to 1.39; 2 RCTs, 121 women), the need for additional pain relief (RR 1.32, 95% CI 0.30 to 5.68; 2 RCTs, 121 women), or maternal adverse effects (RR 3.00, 95% CI 0.13 to 69.52; 2 RCTs, 121 women). 300 mg versus 1200 mg aspirin It is uncertain whether over four hours after administration, 300 mg compared with 1200 mg aspirin has an effect on adequate pain relief (RR 0.62, 95% CI 0.29 to 1.32; 1 RCT, 80 women) or need for additional pain relief (RR 2.00, 95% CI 0.19 to 21.18; 1 RCT, 80 women). There were no maternal adverse effects in either aspirin group. None of the included RCTs reported on neonatal adverse effects. No RCTs reported on secondary review outcomes of: prolonged hospitalisation due to perineal pain; re-hospitalisation due to perineal pain; fully breastfeeding at discharge; mixed feeding at discharge; fully breastfeeding at six weeks; mixed feeding at six weeks; perineal pain at six weeks; maternal views; or maternal postpartum depression.

AUTHORS' CONCLUSIONS

Single dose aspirin may increase adequate pain relief in women with perineal pain post-episiotomy compared with placebo. It is uncertain whether aspirin has an effect on the need for additional analgesia, or on maternal adverse effects, compared with placebo. We downgraded the certainty of the evidence because of study limitations (risk of bias), imprecision, and publication bias. Aspirin may be considered for use in non-breastfeeding women with post-episiotomy perineal pain. Included RCTs excluded breastfeeding women, so there was no evidence to assess the effects of aspirin on neonatal adverse effects or breastfeeding. Future RCTs should be designed to ensure low risk of bias, and address gaps in the evidence, such as the secondary outcomes established for this review. Current research has focused on women with post-episiotomy pain; future RCTs could be extended to include women with perineal pain associated with spontaneous tears or operative birth.

A Comprehensive Review of Over-the-counter Treatment for Chronic Migraine Headaches

PURPOSE OF REVIEW

Migraine headaches are a neurologic disorder characterized by attacks of moderate to severe throbbing headache that are typically unilateral, exacerbated by physical activity, and associated with phonophobia, photophobia, nausea, and vomiting. In the USA, the overall age-adjusted prevalence of migraine in female and male adults is 22.3% and 10.8%, respectively.

RECENT FINDINGS

Migraine is a disabling disease that ranks as the 8th most burdensome disease in the world and the 4th most in women. The overarching hypothesis of migraine pathophysiology describes migraine as a disorder of the pain modulating system, caused by disruptions of the normal neural networks of the head. The activation of these vascular networks results in meningeal vasodilation and inflammation, which is perceived as head pain. The primary goals of acute migraine therapy are to reduce attack duration and severity. Current evidence-based therapies for acute migraine attacks include acetaminophen, four nonsteroidal anti-inflammatory drugs (NSAIDs), seven triptans, NSAID-triptan combinations, dihydroergotamine, non-opioid combination analgesics, and several anti-emetics. Over-the-counter medications are an important component of migraine therapy and are considered a first-line therapy for most migraineurs. These medications, such as acetaminophen, ibuprofen, naproxen, and aspirin, have shown strong efficacy when used as first-line treatments for mild-to-moderate migraine attacks. The lower cost of over-the-counter medications compared with prescription medications also makes them a preferred therapy for some patients. In addition to their efficacy and lower cost, over-the-counter medications generally have fewer and less severe adverse effects, have more favorable routes of administration (oral vs. subcutaneous injection), and reduced abuse potential. The purpose of this review is to provide a comprehensive evidence-based update of over-the-counter pharmacologic options for chronic migraines.

Aspirin (single dose) for perineal pain in the early postpartum period

BACKGROUND

Perineal trauma (due to spontaneous tears, surgical incision (episiotomy) or in association with operative vaginal birth) is common after vaginal birth, and is often associated with postpartum perineal pain. Birth over an intact perineum may also lead to perineal pain. There are adverse health consequences associated with perineal pain for the women and their babies in the short- and long-term, and the pain may interfere with newborn care and the establishment of breastfeeding. Aspirin has been used in the management of postpartum perineal pain and its effectiveness and safety should be assessed.

OBJECTIVES

To determine the efficacy of a single dose of aspirin (acetylsalicylic acid), including at different doses, in the relief of acute postpartum perineal pain.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (30 August 2016), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (31 May 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing single dose aspirin compared with placebo, no treatment, a different dose of aspirin, or single dose paracetamol/acetaminophen for women with perineal pain in the early postpartum period. We planned to include cluster-RCTs but none were identified. Quasi-RCTs and cross-over studies were not eligible for inclusion in this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of the included RCTs. Data were checked for accuracy. The quality of the evidence for the main comparison (aspirin versus placebo) was assessed using the GRADE approach.

MAIN RESULTS

We included 17 RCTs, with 16 involving 1132 women randomised to aspirin or placebo (one RCT did not report numbers of women). Two RCTs (of 16) did not contribute data to review meta-analyses. All women had perineal pain post-episiotomy, and were not breastfeeding. Studies were published between 1967 and 1997, and the risk of bias was often unclear due to poor reporting.We included four comparisons: aspirin versus placebo (data from 15 RCTs); 300 mg versus 600 mg aspirin (1 RCT); 600 mg versus 1200 mg aspirin (2 RCTs); and 300 mg versus 1200 mg aspirin (1 RCT). Primary outcomes Aspirin versus placeboMore women who received aspirin experienced adequate pain relief compared with women who received placebo over four to eight hours after administration (risk ratio (RR) 2.03, 95% confidence intervals (CI) 1.69 to 2.42; 13 RCTs, 1001 women; low-quality evidence). Women who received aspirin were less likely to need additional pain relief over four to eight hours after administration (RR 0.25, 95% CI 0.17 to 0.37; 10 RCTs, 744 women; very low-quality evidence). There was no difference in maternal adverse effects over four to eight hours post-administration (RR 1.08, 95% CI 0.57 to 2.06; 14 RCTs, 1067 women; very low-quality evidence). Subgroup analyses based on dose did not reveal any clear subgroup differences.There was no clear difference over four hours after administration between 300 mg and 600 mg aspirin for adequate pain relief (RR 0.82, 95% CI 0.36 to 1.86; 1 RCT, 81 women) or need for additional pain relief (RR 0.68, 95% CI 0.12 to 3.88; 1 RCT, 81 women). There were no maternal adverse effects in either aspirin group.There was no clear difference over four to eight hours after administration between 600 mg and 1200 mg aspirin for adequate pain relief (RR 0.85, 95% CI 0.52 to 1.39; 2 RCTs, 121 women), need for additional pain relief (RR 1.32, 95% CI 0.30 to 5.68; 2 RCTs, 121 women), or maternal adverse effects (RR 3.00, 95% CI 0.13 to 69.52; 2 RCTs, 121 women).There was no clear difference over four hours after administration between 300 mg and 1200 mg aspirin for adequate pain relief (RR 0.62, 95% CI 0.29 to 1.32; 1 RCT, 80 women) or need for additional pain relief (RR 2.00, 95% CI 0.19 to 21.18; 1 RCT, 80 women). There were no maternal adverse effects in either aspirin group.None of the included RCTs reported on neonatal adverse effects. Secondary outcomesNo studies reported on secondary review outcomes: prolonged hospitalisation due to perineal pain; re-hospitalisation due to perineal pain; fully breastfeeding at discharge; mixed feeding at discharge; fully breastfeeding at six weeks; mixed feeding at six weeks; perineal pain at six weeks; maternal views; maternal postpartum depression.

AUTHORS' CONCLUSIONS

We found low-quality evidence to suggest that single dose aspirin compared with placebo can increase pain relief in women with perineal pain post-episiotomy. Very low-quality evidence also suggested that aspirin can reduce the need for additional analgesia, without increasing maternal adverse effects. Evidence was downgraded based on study limitations (risk of bias), imprecision, and publication bias or both. RCTs excluded breastfeeding women so there is no evidence to assess the effects of aspirin on neonatal adverse effects or breastfeeding.With international guidance recommending mothers initiate breastfeeding within one hour of birth, and exclusively breastfeed for the first six months, the evidence from this review is not applicable to current recommended best practice. Aspirin may be considered for use in non-breastfeeding women with post-episiotomy perineal pain. Although formal assessment was beyond the remit of this review, current guidance suggests that other analgesic drugs (including paracetamol) should be considered first for postpartum perineal pain. Such agents are the focus of other reviews in this series on drugs for perineal pain in the early postpartum period. It is considered most likely that if RCTs are conducted in the future they could compare aspirin with other pain relievers. Future RCTs should be designed to ensure high methodological quality, and address gaps in the evidence, such as the secondary outcomes established for this review. Current research has focused on women with post-episiotomy pain, future RCTs could be extended to women with perineal pain associated with spontaneous tears or operative birth.

Paracetamol/acetaminophen (single administration) for perineal pain in the early postpartum period

BACKGROUND

Perineal pain is a common but poorly studied adverse outcome following childbirth. Pain may result from perineal trauma due to bruising, spontaneous tears, surgical incisions (episiotomies), or in association with operative births (ventouse or forceps assisted births).

OBJECTIVES

To determine the efficacy of a single administration of paracetamol (acetaminophen) systemic drugs used in the relief of acute postpartum perineal pain

SEARCH METHODS

We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 6 November 2012.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing paracetamol (acetaminophen) in a single dose compared with placebo for women with early postpartum perineal pain. We excluded quasi-RCTs and cross-over studies.

DATA COLLECTION AND ANALYSIS

Two review authors assessed each paper for inclusion and extracted data. One review author reviewed the decisions and confirmed calculations for pain relief scores.

MAIN RESULTS

We did not identify any new trials from the updated search so the results remain unchanged as follows.We have included 10 studies describing two dosages of paracetamol. Of these, five studies (526 women) assessed 500 mg to 650 mg and six studies (841 women) assessed 1000 mg of paracetamol. We chose to use random-effects meta-analyses because of the heterogeneity in dosage used. Studies were from the 1970s to the early 1990s, and there was insufficient information to assess the risk of bias adequately, hence the findings need to be interpreted within this context.More women experienced pain relief with paracetamol compared with placebo (average risk ratio (RR) 2.14, 95% confidence interval (CI) 1.59 to 2.89, 10 studies, 1279 women). In addition, there were significantly fewer women having additional pain relief with paracetamol compared with placebo (RR 0.34, 95% CI 0.21 to 0.55, eight studies, 1132 women). Both the 500 mg to 650 mg and 1000 mg doses were effective in providing more pain relief than placebo.Maternal and neonatal potential adverse drug effects were not assessed in any of the included studies. Indeed few secondary outcomes were assessed.

AUTHORS' CONCLUSIONS

More women experienced pain relief, and fewer had additional pain relief, with paracetamol compared with placebo, although potential adverse effects were not assessed and generally the quality of studies was unclear.

Analgesia for relief of pain due to uterine cramping/involution after birth

BACKGROUND

Women may experience differing types of pain and discomfort following birth, including cramping after birth pains associated with uterine involution.

OBJECTIVES

To assess the effectiveness and safety of analgesia for relief of after birth pains following vaginal birth.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2010) and the reference lists of trials and review articles.

SELECTION CRITERIA

All identified published and unpublished randomised controlled trials comparing two different types of analgesia or analgesia with placebo or analgesia with no treatment, for the relief of after birth pains following vaginal birth. Types of analgesia included pharmacological and non-pharmacological.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trial quality and extracted data independently.

MAIN RESULTS

We have included 18 studies (involving 1498 women) in this review. However, only nine of the included studies (with 750 women) reported 24 comparisons of analgesia with other analgesia or placebo and had data that could be included in our meta-analyses. The majority of studies investigated pharmacological analgesics and these were grouped into classes for this review. Non-steroidal anti-inflammatory drugs (NSAIDs) were significantly better than placebo at relieving pain from uterine involution as assessed by their summed pain intensity differences (SPID) (mean difference (MD) 4.34; 95% confidence interval (CI) 2.87 to 5.82; three studies, 204 women) and summed pain relief scores (MD 5.94; 95% CI 3.83 to 8.01; three studies, 204 women). NSAIDS were compared with opioids in one small study of 23 women reporting SPID and summed pain relief and found no difference. A larger study of 127 women found NSAIDs to be significantly better than opioids at reducing pain intensity six hours following study intervention (MD -0.70; 95% CI -1.04 to -0.35). Opioids were compared with placebo in three studies that could be included in meta-analyses; one small study of 23 women reporting SPID and summed pain relief and found no difference. One study of 95 women found no difference in pain intensity six hours following the study intervention. A third study of 108 women found significantly more women in the placebo group reported no pain relief than women in the opioid group (risk ratio 0.10; 95% CI 0.04 to 0.23). Aspirin was significantly better than paracetamol when pain intensity score was assessed six hours after study intervention (MD 0.85; 95% CI 0.29 to 1.41; one study 48 women) at relieving pain from uterine involution. Paracetamol was not better than placebo when pain intensity was assessed six hours after the study intervention in one study of 48 women.

AUTHORS' CONCLUSIONS

Non-steroidal anti-inflammatory drugs (NSAID) including aspirin were better than placebo at relieving pain from uterine cramping/involution following vaginal birth. NSAIDs were better than paracetamol and paracetamol was not better than placebo, though numbers of participants for these comparisons were small. Data for opioids compared with NSAIDs and opioids compared with placebo were conflicting, with some measures showing similar effect and others indicating NSAIDs were better than opioids and opioids were not better than placebo. There were insufficient data to make conclusions regarding the effectiveness of opioids at relieving pain from uterine cramping/involution.The median year of publication of included studies was 1981; therefore more research is needed to assess the effectiveness of current pharmacological and non-pharmacological analgesia at relieving pain from uterine cramping/involution following vaginal birth.

Paracetamol/acetaminophen (single administration) for perineal pain in the early postpartum period

BACKGROUND

Perineal pain is a common but poorly studied adverse outcome following childbirth. Pain may result from perineal trauma due to bruising, spontaneous tears, surgical incisions (episiotomies), or in association with operative births (ventouse or forceps assisted births).

OBJECTIVES

To determine the efficacy of a single administration of paracetamol (acetaminophen) systemic drugs used in the relief of acute postpartum perineal pain

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing paracetamol (acetaminophen) in a single dose compared with placebo for women with early postpartum perineal pain. We excluded quasi-RCTs and cross-over studies.

DATA COLLECTION AND ANALYSIS

Two review authors assessed each paper for inclusion and extracted data. One review author reviewed the decisions and confirmed calculations for pain relief scores.

MAIN RESULTS

We have included 10 studies describing two dosages of paracetamol. Of these, five studies (526 women) assessed 500 mg to 650 mg and six studies (841 women) assessed 1000 mg of paracetamol. We chose to use random-effects meta-analyses because of the heterogeneity in dosage used. Studies were from the 1970s to the early 1990s, and there was insufficient information to assess the risk of bias adequately, hence the findings need to be interpreted within this context.More women experienced pain relief with paracetamol compared with placebo (average risk ratio (RR) 2.14, 95% confidence interval (CI) 1.59 to 2.89, 10 studies, 1279 women). In addition, there were significantly fewer women having additional pain relief with paracetamol compared with placebo (RR 0.34, 95% CI 0.21 to 0.55, eight studies, 1132 women). Both the 500 mg to 650 mg and 1000 mg doses were effective in providing more pain relief than placebo.Maternal and neonatal potential adverse drug effects were not assessed in any of the included studies. Indeed few secondary outcomes were assessed.

AUTHORS' CONCLUSIONS

More women experienced pain relief, and fewer had additional pain relief, with paracetamol compared with placebo, although potential adverse effects were not assessed and generally the quality of studies was unclear.

Combining paracetamol (acetaminophen) with nonsteroidal antiinflammatory drugs: a qualitative systematic review of analgesic efficacy for acute postoperative pain

BACKGROUND

There has been a trend over recent years for combining a nonsteroidal antiinflammatory drug (NSAID) with paracetamol (acetaminophen) for pain management. However, therapeutic superiority of the combination of paracetamol and an NSAID over either drug alone remains controversial. We evaluated the efficacy of the combination of paracetamol and an NSAID versus either drug alone in various acute pain models.

METHODS

A systematic literature search of Medline, Embase, Cumulative Index to Nursing and Allied Health Literature, and PubMed covering the period from January 1988 to June 2009 was performed to identify randomized controlled trials in humans that specifically compared combinations of paracetamol with various NSAIDs versus at least 1 of these constituent drugs. Identified studies were stratified into 2 groups: paracetamol/NSAID combinations versus paracetamol or NSAIDs. We analyzed pain intensity scores and supplemental analgesic requirements as primary outcome measures. In addition, each study was graded for quality using a validated scale.

RESULTS

Twenty-one human studies enrolling 1909 patients were analyzed. The NSAIDs used were ibuprofen (n = 6), diclofenac (n = 8), ketoprofen (n = 3), ketorolac (n = 1), aspirin (n = 1), tenoxicam (n = 1), and rofecoxib (n = 1). The combination of paracetamol and NSAID was more effective than paracetamol or NSAID alone in 85% and 64% of relevant studies, respectively. The pain intensity and analgesic supplementation was 35.0% +/- 10.9% and 38.8% +/- 13.1% lesser, respectively, in the positive studies for the combination versus paracetamol group, and 37.7% +/- 26.6% and 31.3% +/- 13.4% lesser, respectively, in the positive studies for the combination versus the NSAID group. No statistical difference in median quality scores was found between experimental groups.

CONCLUSION

Current evidence suggests that a combination of paracetamol and an NSAID may offer superior analgesia compared with either drug alone.

Single dose oral paracetamol (acetaminophen) for postoperative pain in adults

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 1, 2004 - this original review had been split from a previous title on 'Single dose paracetamol (acetaminophen) with and without codeine for postoperative pain'. The last version of this review concluded that paracetamol is an effective analgesic for postoperative pain, but additional trials have since been published. This review sought to evaluate the efficacy and safety of paracetamol using current data, and to compare the findings with other analgesics evaluated in the same way.

OBJECTIVES

To assess the efficacy of single dose oral paracetamol for the treatment of acute postoperative pain.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE, the Oxford Pain Relief Database and reference lists of articles to update an existing version of the review in July 2008.

SELECTION CRITERIA

Randomised, double-blind, placebo-controlled clinical trials of paracetamol for acute postoperative pain in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. Area under the "pain relief versus time" curve was used to derive the proportion of participants with paracetamol or placebo experiencing at least 50% pain relief over four to six hours, using validated equations. Number-needed-to-treat-to-benefit (NNT) was calculated, with 95% confidence intervals (CI). The proportion of participants using rescue analgesia over a specified time period, and time to use, were sought as measures of duration of analgesia. Information on adverse events and withdrawals was also collected.

MAIN RESULTS

Fifty-one studies, with 5762 participants, were included: 3277 participants were treated with a single oral dose of paracetamol and 2425 with placebo. About half of participants treated with paracetamol at standard doses achieved at least 50% pain relief over four to six hours, compared with about 20% treated with placebo. NNTs for at least 50% pain relief over four to six hours following a single dose of paracetamol were as follows: 500 mg NNT 3.5 (2.7 to 4.8); 600 to 650 mg NNT 4.6 (3.9 to 5.5); 975 to 1000 mg NNT 3.6 (3.4 to 4.0). There was no dose response. Sensitivity analysis showed no significant effect of trial size or quality on this outcome.About half of participants needed additional analgesia over four to six hours, compared with about 70% with placebo. Five people would need to be treated with 1000 mg paracetamol, the most commonly used dose, to prevent one needing rescue medication over four to six hours, who would have needed it with placebo. Adverse event reporting was inconsistent and often incomplete. Reported adverse events were mainly mild and transient, and occurred at similar rates with 1000 mg paracetamol and placebo. No serious adverse events were reported. Withdrawals due to adverse events were uncommon and occurred in both paracetamol and placebo treatment arms.

AUTHORS' CONCLUSIONS

A single dose of paracetamol provides effective analgesia for about half of patients with acute postoperative pain, for a period of about four hours, and is associated with few, mainly mild, adverse events.

Analgetikakombinationen zur postoperativen Schmerztherapie

BACKGROUND

The supplementation of an opioid by a non-opioid analgesic is a widely accepted technique for the treatment of postoperative pain. However, it is still unclear whether a combination of different non-opioids has an advantage in terms of an improved analgesia and/or a reduction of the opioid-related adverse effects.

METHODOLOGY

A systematic analysis of the literature was performed searching for randomized, controlled trials studying the effects of a combination of two non-opioid analgesics in order to reduce postoperative opioid requirements and/or postoperative pain. Significant reduction of the postoperative opioid requirement and/or postoperative pain were defined as main rating criteria. To facilitate comparisons between the trials, the relative (proportional) reduction of postoperative opioid administration and the relative reduction of postoperative pain were calculated on defined pain scales.

RESULTS

A total of 25 trials were identified, mainly studies comparing non-steroidal anti-inflammatory drugs (NSAIDs) with paracetamol. Only 3 trials found a statistically improved analgesic efficacy and 15 studies did not show any relevant improvement or the combination group was only significantly superior to one of the groups receiving monotherapy. A further seven studies could not be evaluated due to methodological issues. There was no evidence for a significant reduction of opioid-induced adverse effects.

CONCLUSION

A combination of non-opioid analgesics, in particular NSAIDs with paracetamol, cannot be recommended at present due to the lack of data showing improved effectiveness.

Randomized controlled noninferiority trial to compare extended release acetaminophen and ibuprofen for the treatment of ankle sprains

STUDY OBJECTIVE

To compare acetaminophen extended release 1,300 mg 3 times daily and ibuprofen 400 mg 3 times daily for treatment of signs and symptoms of grade I or II lateral ankle sprains.

METHODS

Patients (N=260) 18 years or older and with grade I or II lateral ankle sprains were randomized to receive acetaminophen extended release 1,300 mg 3 times daily or ibuprofen 400 mg 3 times daily for 9 days. Primary endpoint was change from baseline at day 4 in pain on walking. Other endpoints included change from baseline at day 9 in pain on walking; change from baseline at days 4 and 9 in ability to walk and ankle swelling, bruising, and range of motion; satisfaction with treatment on days 4 and 9; percentage of patients with positive anterior drawer test on day 4; and time to resume normal activity. Safety assessments consisted of reported adverse events. This study had a noninferiority design in which the hypothesis was that acetaminophen extended release was not inferior to ibuprofen for treatment of signs and symptoms of grade I or II lateral ankle sprains.

RESULTS

The difference in least squares means (acetaminophen extended release, ibuprofen) with respect to the primary endpoint within the per-protocol population was -0.88; acetaminophen extended release was comparable to ibuprofen for the primary endpoint because the upper limit (3.26) of the 1-sided 95% confidence interval (CI) for the difference in least squares means did not exceed the noninferiority limit of 6.90. The intention-to-treat population was used to test the second step of the 2-step testing process because the null hypothesis was rejected in the noninferiority test. For this analysis, the difference between acetaminophen extended release and ibuprofen in the least squares mean change from baseline for the primary endpoint was -1.63 (not significant). Results showed that acetaminophen extended release was noninferior to ibuprofen with respect to the secondary endpoints. No serious drug-related adverse events were reported. The most common adverse events, reported by 6.5% of patients, were in the gastrointestinal system (mainly nausea and upper abdominal pain).

CONCLUSION

Acetaminophen extended release 3,900 mg daily was comparable to ibuprofen 1,200 mg daily for treatment of grade I or II lateral ankle sprains. Both treatments were well tolerated.

Predicting postoperative analgesia outcomes: NNT league tables or procedure-specific evidence?

Number needed to treat (NNT) values have been recommended and used to assess efficacy of analgesics for acute pain management. However, the data analysed come from a variety of procedures, which may potentially hinder the interpretation of the NNT value for specific procedures. We reanalysed available NNT data with acetaminophen in relation to the magnitude of surgical injury. Acetaminophen was less effective for pain relief after orthopaedic procedures than after dental procedures. The relative risk ratio for more than 50% pain relief, compared with placebo, was only 1.87 compared with 3.77 (P<0.05). Although NNT can give a valuable overview of efficacy, this concept is not necessarily applicable to all types of surgery. We suggest that estimates of NNT should be related to specific surgical procedures.

Single dose oral paracetamol (acetaminophen) for postoperative pain

BACKGROUND

Paracetamol (acetaminophen) and non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for the relief of mild and moderate pain arising from headache, musculoskeletal conditions and dysmenorrhoea. A prior Cochrane systematic review concluded that paracetamol is also effective for postoperative pain, but additional trials have since been published. This review sought to evaluate the efficacy and safety of paracetamol using current data, and to compare the findings with other analgesics evaluated in the same way.

OBJECTIVES

To assess the efficacy of single dose oral paracetamol for the treatment of acute postoperative pain.

SEARCH STRATEGY

We searched the Cochrane Library (Issue 3, 2002), the trials register of the Cochrane Pain, Palliative and Supportive Care group (November 2002); MEDLINE (1966 to May 1996); PubMed (1996 to August 2001); EMBASE (1980 to 1996); the Oxford Pain Relief Database (1950 to 1994); and reference lists of articles in order to update an existing version of the review.

SELECTION CRITERIA

Randomised, double-blind, placebo-controlled clinical trials of paracetamol for acute postoperative pain in adults.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data. The area under the 'pain relief versus time' curve was used to derive the proportion of patients with paracetamol or placebo experiencing least 50% pain relief over four to six hours using validated equations. The number-needed-to-treat (NNT) was calculated using 95% confidence intervals. Information on adverse effects was also collected.

MAIN RESULTS

Forty-seven reports that enrolled 4186 patients (2561 patients were treated with a single oral dose of paracetamol and 1625 with placebo) met the inclusion criteria and were included in the analyses. The NNTs for at least 50% pain relief over four to six hours following a single dose of paracetamol were as follows: 325 mg NNT 3.8 (2.2 to 13.3); 500 mg NNT 3.5 (2.7 to 4.8); 600/650 mg NNT 4.6 (3.9 to 5.5); 975/1000 mg NNT 3.8 (3.4 to 4.4); and 1500 mg NNT 3.7 (2.3 to 9.5). Sub-group analysis showed no significant differences between smaller and larger trials, or lower and higher quality trials. Drug-related study withdrawals were rarely reported. Studies reported a variable incidence of adverse effects that were generally mild and transient. There were no statistically significant differences in the frequency of reported adverse effects between paracetamol 975/1000 mg and placebo.

REVIEWER'S CONCLUSIONS

Single doses of paracetamol are effective analgesics for acute postoperative pain and give rise to few adverse effects.

A benefit-risk assessment of caffeine as an analgesic adjuvant

Caffeine has been an additive in analgesics for many years. However, the analgesic adjuvant effects of caffeine have not been seriously investigated since a pooled analysis conducted in 1984 showed that caffeine reduces the amount of paracetamol (acetaminophen) necessary for the same effect by approximately 40%. In vitro and in vivo pharmacological research has provided some evidence that caffeine can have anti-nociceptive actions through blockade of adenosine receptors, inhibition of cyclo-oxygenase-2 enzyme synthesis, or by changes in emotion state. Nevertheless, these actions are only considered in some cases. It is suggested that the actual doses of analgesics and caffeine used can influence the analgesic adjuvant effects of caffeine, and doses that are either too low or too high lead to no analgesic enhancement. Clinical trials suggest that caffeine in doses of more than 65 mg may be useful for enhancement of analgesia. However, except for in headache pain, the benefits are equivocal. While adding caffeine to analgesics increases the number of patients who become free from headache [rate ratio = 1.36, 95% confidence interval (CI) 1.17 to 1.58], it also leads to more patients with nervousness and dizziness (relative risk = 1.60, 95% CI 1.26 to 2.03). It is suggested that long-term use or overuse of analgesic medications is associated with rebound headache. However, there is no robust evidence that headache after use or withdrawal of caffeine-containing analgesics is more frequent than after other analgesics. Case-control studies have shown that caffeine-containing analgesics are associated with analgesic nephropathy (odds ratio = 4.9, 95% CI 2.3 to 10.3). However, no specific contribution of caffeine to analgesic nephropathy can be identified from these studies. Whether caffeine produces nephrotoxicity on its own, or increases nephrotoxicity due to analgesics, is yet to be established.

Comparative effect of paracetamol, NSAIDs or their combination in postoperative pain management: a qualitative review

BACKGROUND

Quantitative reviews of postoperative pain management have demonstrated that the number of patients needed to treat for one patient to achieve at least 50% pain relief (NNT) is 2.7 for ibuprofen (400 mg) and 4.6 for paracetamol (1000 mg), both compared with placebo. However, direct comparisons between paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs) have not been extensively reviewed. The aims of this review are (i) to compare the analgesic and adverse effects of paracetamol with those of other NSAIDs in postoperative pain, (ii) to compare the effects of combined paracetamol and NSAID with those of either drug alone, and (iii) to discuss whether the adverse effects of NSAIDs in short-term use are justified by their analgesic effects, compared with paracetamol.

METHODS

Medline (1966 to January 2001) and the Cochrane Library (January 2001) were used to perform a systematic, qualitative review of postoperative pain studies comparing paracetamol (minimum 1000 mg) with NSAID in a double-blind, randomized manner. A quantitative review was not performed as too many studies of high scientific standard (27 out of 41 valid studies, including all major surgery studies) would have been excluded.

RESULTS

NSAIDs were clearly more effective in dental surgery, whereas the efficacy of NSAIDs and paracetamol seemed without substantial differences in major and orthopaedic surgery, although firm conclusions could not be made because the number of studies was limited. The addition of an NSAID to paracetamol may confer additional analgesic efficacy compared with paracetamol alone, and the limited data available also suggest that paracetamol may enhance analgesia when added to an NSAID, compared with NSAIDs alone.

CONCLUSION

Paracetamol is a viable alternative to the NSAIDs, especially because of the low incidence of adverse effects, and should be the preferred choice in high-risk patients. It may be appropriate to combine paracetamol with NSAIDs, but future studies are required, especially after major surgery, with specific focus on a potential increase in side-effects from their combined use.

Single dose paracetamol (acetaminophen), with and without codeine, for postoperative pain

BACKGROUND

Patient surveys have shown that postoperative pain is often not managed well, and there is a need to assess the efficacy and safety of commonly used analgesics as newer treatments become available. Paracetamol (acetaminophen) is an important non-opiate analgesic, commonly prescribed, as well as being available for retail sale. This review seeks to examine the efficacy of paracetamol alone and in combination with codeine, and also considers adverse effects.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of a single dose of oral paracetamol (acetaminophen) alone and in combination with codeine for moderate to severe postoperative pain.

SEARCH STRATEGY

Published trials were identified from: Medline (1966 to May 1996), Embase (1980 to 1996), Cochrane Library (Issue 2 1996) and the Oxford Pain Relief Database (1950 to 1994). Additional trials were identified from reference lists of retrieved studies. Date of most recent searches: July 1998.

SELECTION CRITERIA

Inclusion criteria were: full journal publication, postoperative pain, postoperative oral administration, adult patients, baseline pain of moderate to severe intensity, double-blind design, and random allocation to treatment groups which compared paracetamol with placebo or a combination of paracetamol and codeine with either placebo or the same dose of paracetamol alone.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent reviewers, and trials were quality scored. Summed pain intensity and pain relief data were extracted and converted into dichotomous information to yield the number of patients with at least 50% pain relief. This was used to calculate the relative benefit and number-needed-to-treat (NNT) for one patient to achieve at least 50% pain relief over 4 to 6 hours compared with placebo. Adverse effects were used to calculate relative risk and number-needed-to-harm (NNH).

MAIN RESULTS

We found 40 trials of paracetamol against placebo (4171 patients), 22 trials of paracetamol plus codeine against placebo (1407 patients) and 12 trials of paracetamol plus codeine against the same dose of paracetamol (794 patients). In postoperative pain paracetamol 1000 mg had an NNT of 4.6 (3.8-5.4) for at least 50% pain relief when compared with placebo, and paracetamol 600/650 mg had an NNT of 5.3 (4.1-7.2). Paracetamol 600/650 mg plus codeine 60 mg had an NNT of 3. 6 (2.9-4.5). Comparing paracetamol plus codeine 60 mg with the same dose of paracetamol alone gave an NNT of 7.7 (5.1-17) for at least 50% pain relief. Adverse effects: Relative risk estimates for paracetamol 600/650 mg plus codeine 60 mg versus placebo showed a significant difference for 'drowsiness'/somnolence (NNH 11 (7.5- 0)) and dizziness (NNH 27 (15-164)) but no significant difference for nausea/vomiting.

REVIEWER'S CONCLUSIONS

Paracetamol is an effective analgesic with a low incidence of adverse effects. The addition of codeine 60 mg to paracetamol produces additional pain relief even in single oral doses, but may be accompanied by an increase in drowsiness and dizziness.

Analgesic efficacy of paracetamol and its combination with codeine and caffeine in surgical pain--a meta-analysis

The objective of this study was to quantify the analgesic efficacy of paracetamol and its combination with codeine or caffeine through a systematic overview and meta-analysis of relevant randomized controlled trials (RCTs). Systematic retrieval of relevant clinical trials was carried out using computerized searches, historical searches and communication with manufacturers. The results of RCTs were pooled to estimate (i) the difference in percentage improvement of total pain relief (TOTPAR%) and the sum of pain intensity difference (SPID%); (ii) the proportions of patients obtaining moderate to excellent pain relief relative to placebo (ResRR) and (iii) the ratio of patients requiring analgesic re-medication (RemRR). Head-to-head comparisons were also undertaken for paracetamol versus its combination with codeine or caffeine. A total of 80 RCT reports describing 103 placebo comparisons and 26 head-to-head comparisons were identified. The total pain relief score in the single dose studies increased by 38 percentage points for paracetamol and by 24 points for placebo. The difference (d) in TOTPAR% between the two was highly significant (d = 14, 95% CI: 12, 16). For the difference in SPID%, d = 12, 95% CI: 11, 13. Patients were more than twice as likely to obtain moderate to excellent pain relief on paracetamol than on placebo (ResRR = 2.39, 95% CI: 1.89, 3.02), and less likely to require re-medication (RemRR = 0.78, 95% CI: 0.69, 0.88). There was no significant (P > 0.05) dose-response relationship. The analgesic efficacy of paracetamol 600 mg was enhanced with the addition of codeine 60 mg (using TOTPAR% as outcome) in both indirect and head-to-head comparisons. SPID%, but not ResRR and RemRR, data supported this conclusion. Much weaker effects were observed with the caffeine combination. Adverse effects were mild. Surprisingly, drowsiness was seen more often with paracetamol and paracetamol-codeine combinations than with placebo. The relative risks (95% CI) were 1.83 (1.29, 2.59) and 2.39 (1.58, 3.57), respectively. In conclusion paracetamol is an effective analgesic for post-surgical pain. Caffeine adds little to the analgesic effect of paracetamol. However, there is some evidence that codeine 60 mg adds to the analgesic effects of paracetamol 600 mg, using pain relief or pain intensity scores as outcomes, but this is not necessarily translated into an increase in number of patients who obtain moderate to excellent pain relief.