Efficacy and pharmacokinetics of aspirin in post-operative dental pain

Aspirin in Hepatocellular Carcinoma

Preclinical and clinical studies provide evidence for aspirin as a preventative agent for cancer. Compelling direct evidence supports a chemopreventive effect of aspirin in individuals at high risk of developing colorectal cancer due to Lynch syndrome, while indirect evidence indicates that aspirin may reduce the risk of and mortality from sporadic colorectal cancer. There is weaker evidence for a protective effect of aspirin against all cancers taken as a group. Nevertheless, the results of recent retrospective cohort studies consistently indicate a beneficial effect of aspirin as a chemopreventive or adjuvant chemotherapeutic agent in hepatocellular carcinoma (HCC). Epidemiologic studies conducted in the general population or in selected populations at higher risk for HCC reveal that regular aspirin use is associated with reduced HCC incidence. In addition, aspirin may act as an adjuvant to other therapies in reducing HCC recurrence. According to studies in animal models, the cancer-preventative effect of aspirin may be related to its antiplatelet and anti-inflammatory activities. Prospective studies are warranted to determine whether aspirin should be recommended to diverse populations of patients at risk for HCC.

Aspirin reduces lipopolysaccharide-induced pulmonary inflammation in human models of ARDS

RATIONALE

Platelets play an active role in the pathogenesis of acute respiratory distress syndrome (ARDS). Animal and observational studies have shown aspirin's antiplatelet and immunomodulatory effects may be beneficial in ARDS.

OBJECTIVE

To test the hypothesis that aspirin reduces inflammation in clinically relevant human models that recapitulate pathophysiological mechanisms implicated in the development of ARDS.

METHODS

Healthy volunteers were randomised to receive placebo or aspirin 75  or 1200 mg (1:1:1) for seven days prior to lipopolysaccharide (LPS) inhalation, in a double-blind, placebo-controlled, allocation-concealed study. Bronchoalveolar lavage (BAL) was performed 6 hours after inhaling 50 µg of LPS. The primary outcome measure was BAL IL-8. Secondary outcome measures included markers of alveolar inflammation (BAL neutrophils, cytokines, neutrophil proteases), alveolar epithelial cell injury, systemic inflammation (neutrophils and plasma C-reactive protein (CRP)) and platelet activation (thromboxane B2, TXB2). Human lungs, perfused and ventilated ex vivo (EVLP) were randomised to placebo or 24 mg aspirin and injured with LPS. BAL was carried out 4 hours later. Inflammation was assessed by BAL differential cell counts and histological changes.

RESULTS

In the healthy volunteer (n=33) model, data for the aspirin groups were combined. Aspirin did not reduce BAL IL-8. However, aspirin reduced pulmonary neutrophilia and tissue damaging neutrophil proteases (Matrix Metalloproteinase (MMP)-8/-9), reduced BAL concentrations of tumour necrosis factor α and reduced systemic and pulmonary TXB2. There was no difference between high-dose and low-dose aspirin. In the EVLP model, aspirin reduced BAL neutrophilia and alveolar injury as measured by histological damage.

CONCLUSIONS

These are the first prospective human data indicating that aspirin inhibits pulmonary neutrophilic inflammation, at both low and high doses. Further clinical studies are indicated to assess the role of aspirin in the prevention and treatment of ARDS.

TRIAL REGISTRATION NUMBER

NCT01659307 Results.

Mode of action of aspirin as a chemopreventive agent

Aspirin taken for several years at doses of at least 75 mg daily reduced long-term incidence and mortality due to colorectal cancer. The finding of aspirin benefit at low-doses given once daily, used for cardioprevention, locates the antiplatelet effect of aspirin at the center of its antitumor efficacy. In fact, at low-doses, aspirin acts mainly by an irreversible inactivation of platelet cyclooxygenase (COX)-1 in the presystemic circulation, which translates into a long-lasting inhibition of platelet function. Given the short half-life of aspirin in the human circulation(approximately 20 min) and the capacity of nucleated cells to resynthesize the acetylated COX-isozyme(s), it seems unlikely that a nucleated cell could be the target of aspirin chemoprevention. These findings convincingly suggest that colorectal cancer and atherothrombosis may share a common mechanism of disease, i.e. platelet activation in response to epithelial(in tumorigenesis) and endothelial(in tumorigenesis and atherothrombosis) injury. Activated platelets may also enhance the metastatic potential of cancer cells (through a direct interaction and/or the release of soluble mediators or exosomes) at least in part by inducing the overexpression of COX-2. COX-independent mechanisms of aspirin, such as the inhibition of NF-kB signaling and Wnt/β-catenin signaling and the acetylation of extra-COX proteins, have been suggested to play a role in its chemopreventive effects. However, their relevance remains to be demonstrated in vivo at clinical doses.

Mechanistic and pharmacological issues of aspirin as an anticancer agent

Recent findings have shown that aspirin, taken for several years, reduces the long-term risk of some cancers, particularly colorectal cancer. The result that aspirin benefit is detectable at daily low-doses (at least 75mg), the same used for the prevention of cardiovascular disease, positions the antiplatelet action of aspirin at the center of its antitumor efficacy. At low-doses given every 24 h, aspirin is acting by a complete and persistent inhibition of cyclooxygenase (COX)-1 in platelets (in the pre-systemic circulation) while causing a limited and rapidly reversible inhibitory effect on COX-2 and/or COX-1 expressed in nucleated cells. Aspirin has a short half-life in human circulation (approximately 20 min); nucleated cells have the ability to resynthesize the acetylated COX-isozymes within a few hours, while platelets do not. COX-independent mechanisms of aspirin, such as the inhibition of Wnt/ β-catenin and NF-kB signaling and the acetylation of extra-COX proteins, have been suggested to play a role in its chemo-preventive effects, but their relevance remains to be demonstrated in vivo at clinical doses. In conclusion, the results of clinical pharmacology and the analysis of randomized and epidemiological studies suggest that colorectal cancer and atherothrombosis share a common mechanism of disease, i.e. enhanced platelet activation in response to injury at distinct sites.

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.

Demonstration of the analgesic efficacy and dose-response of acetylsalicylic acid with pseudoephedrine

To determine acute analgesia by acetylsalicylic acid (ASA) when combined with pseudoephedrine (PSE) in patients with upper respiratory tract infection (URTI), we used the sore throat pain model to measure single-dose effects of ASA 500 mg/PSE 30 mg, ASA 1000 mg/PSE 60 mg, and acetaminophen (APAP) 1000 mg/PSE 60 mg (serving as a positive control). Under double-blind, randomized, placebo-controlled conditions, 640 adult patients with confirmed acute pharyngitis and rhinosinusitis associated with URTI rated throat pain intensity and relief at intervals over 6 hours. Efficacy was demonstrated for both doses of ASA/PSE compared with placebo for all end points, including total pain relief and summed pain intensity differences, beginning at 20 minutes on both scales (all P < .05), and the efficacy of APAP/PSE compared with placebo was confirmed (P < .01). Greater differences in pain relief and intensity were also demonstrated between the higher and lower doses of ASA/PSE (P < .05), in particular, among 329 patients with severe pain, as well as between ASA 1000 mg/PSE 60 mg and APAP 1000 mg/PSE 60 mg (P < .05). No serious adverse events were reported. This study demonstrates that ASA is a well-tolerated and effective analgesic in 500- and 1000-mg doses when combined with pseudoephedrine.

Inhibitory activity of salicylic acid on lipoxygenase-dependent lipid peroxidation

BACKGROUND

Since iron is essential for lipoxygenase activity and salicylic acid (SA) can interact with the metal, possible lipoxygenase inhibition by SA was investigated.

METHODS

Kinetic spectrophotometric evaluation of enzymatic lipid peroxidation catalyzed by soybean lipoxygenase (SLO), rabbit reticulocyte 15-lipoxygenase (RR15-LOX), porcine leukocyte 12-lipoxygenase (PL12-LOX) and human recombinant 5-lipoxygenase (HR5-LOX) with and without SA.

RESULTS

SA inhibited linoleic, arachidonic and docosahexaenoic acid or human lipoprotein peroxidation catalyzed by SLO with IC50 of, respectively, 107, 153, 47 and 108 microM. Using the same substrates, SA inhibited RR15-LOX with IC50 of, respectively, 49, 63, 27 and 51 microM. Further, arachidonic acid peroxidation catalyzed by PL12-LOX and HR5-LOX was inhibited by SA with IC50 of 101 and 168 microM, respectively. Enzymatic inhibition was complete, reversible and non-competitive. Conceivably due to its lower hydrophobicity, aspirin was less effective, indicating acetylation-independent enzyme inhibition. SA and aspirin were ineffective peroxyl radical scavengers but readily reduced Fe3+, i.e. FeCl3, to Fe2+, suggesting their capacity to reduce Fe3+ at the enzyme active site. Indeed, similar to the catecholic redox inhibitor nordihydroguaiaretic acid, SA inhibited with the same efficiency both ferric and the native ferrous SLO form, indicating that these compounds reduce the active ferric enzyme leading to its inactivation.

GENERAL SIGNIFICANCE

SA can inhibit lipoxygenase-catalyzed lipid peroxidation at therapeutic concentrations, suggesting its possible inhibitory activity against enzymatic lipid peroxidation in the clinical setting.

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.

Over-the-counter analgesics and antipyretics: a critical assessment

BACKGROUND

It is just 100 years since the introduction of aspirin to medicine. Since then, aspirin and its derivatives have been joined by acetaminophen, and the nonsteroidal anti-inflammatory drugs--ibuprofen, naproxen sodium, and ketoprofen--as the only over-the-counter (OTC) agents approved by the US Food and Drug Administration for the short-term treatment of pain, headache, dysmenorrhea, and fever. Recently the prescription use of aspirin has expanded to include a number of antiplatelet indications.

OBJECTIVE

The purpose of this paper is to review critically the history, mechanisms of action, efficacy, and tolerability of OTC analgesic and antipyretic products. Relatively new and potential future indications for these drugs are also discussed.

CONCLUSION

Although all of the OTC analgesic/antipyretic agents seem to share a common mechanism of prostaglandin inhibition, there are important differences in their pharmacology, efficacy, and side-effect profiles. Considering their often-unsupervised use, the risk-benefit ratio of this class of drugs has been extremely favorable. However, when used inappropriately, even these drugs pose significant risks to certain patient populations.

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.

Are the pharmacokinetics of ibuprofen important determinants for the drug's efficacy in postoperative pain after third molar surgery?

The aim of the present placebo-controlled, crossover study was to evaluate the efficacy and pharmacokinetics of ibuprofen after a single oral dose of soluble ibuprofen 400 mg in 18 patients with postoperative pain after bilateral third molar surgery. Throughout a 5-hour investigation period, patients reported significantly less pain (P < 0.001) after treatment with soluble ibuprofen than after placebo. Peak plasma concentrations of ibuprofen occurred approximately 30 minutes after dosage. No significant correlations (P > 0.05) were observed between efficacy measures and the various pharmacokinetic parameters (AUC0-300, Cmax and Tmax) for ibuprofen after the soluble dose. It is concluded that a single dose of soluble ibuprofen 400 mg is an effective analgesic for the control of postoperative pain in the early period after third molar surgery. Efficacy of this preparation does not appear to be directly related to the drug's pharmacokinetic variables in plasma.

Topical acetylsalicylic, salicylic acid and indomethacin suppress pain from experimental tissue acidosis in human skin

Topically applied acetylsalicylic acid (ASA), salicylic acid (SA) and indomethacin were tested in an experimental pain model that provides direct nociceptor excitation through cutaneous tissue acidosis. In 30 volunteers, sustained burning pain was produced in the palmar forearm through a continuous intradermal pressure infusion of a phosphate-buffered isotonic solution (pH 5.2). In 5 different, double-blind, randomized cross-over studies with 6 volunteers each, the flow rate of the syringe pump was individually adjusted to result in constant pain ratings of around 20% (50% in study 4) on a visual analog scale (VAS). The painful skin area was then covered with either placebo or the drugs which had been dissolved in diethylether. In the first study on 6 volunteers, ASA (60 mg/ml) or lactose (placebo) in diethylether (10 ml) was applied, using both arms at 3-day intervals. Both treatments resulted in sudden and profound pain relief due to the cooling effect of the evaporating ether. With lactose, however, the mean pain rating was restored close to the baseline within 6-8 min while, with ASA, it remained significantly depressed for the rest of the observation period (another 20 min). This deep analgesia was not accompanied by a loss of tactile sensation. The further studies served to show that indomethacin (4.5 mg/ml) and SA (60 mg/ml) were equally effective as ASA (each 92-96% pain reduction) and that the antinociceptive effects were due to local but not systemic actions, since ASA and SA dis not reach measurable plasma levels up to 3 h after topical applications. With a higher flow rate of acid buffer producing more intense pain (VAS 50%). ASA and SA were still able to significantly reduce the ratings by 90% or 84%, respectively. On the other hand, by increasing the flow rate by a factor of 2 on average, during the period of fully developed drug effect it was possible to overcome the pain suppression, which suggests a competitive mechanism of (acetyl-) salicylic antinociception.

Nonsteroidal anti-inflammatory drugs in perisurgical pain management. Mechanisms of action and rationale for optimum use

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a group of agents with similar actions but diverse chemical structures. Aspirin (acetylsalicylic acid) and sodium salicylate were the first drugs of this type to be used clinically. However, over the past 3 decades there has been a dramatic increase in the number of NSAIDs available for the treatment of postoperative pain. Tissue injury, such as occurs with surgical intervention, is associated with the release of numerous inflammatory mediators including prostaglandins. Prostaglandins derived from the arachidonic acid cascade are implicated in the production of inflammatory pain, and in sensitising nociceptors to the actions of other mediators. They are synthesised from arachidonic acid via the endoperoxide biosynthesis pathway, the initial step of which is catalysed by the enzyme cyclo-oxygenase. Two forms of the cyclo-oxygenase enzyme (COX-1 and COX-2) have been characterised. COX-1 is important in circumstances where prostaglandins have a protective effect such as gastric mucus production and renal blood flow maintenance. NSAIDs inhibit the synthesis of prostaglandins at 1 or more points in the endoperoxide pathway. Three mechanisms of inhibition of the biosynthetic enzymes have been proposed: (i) rapid, reversible competitive inhibition; (ii) irreversible, time-dependent inhibition; and (iii) rapid, reversible noncompetitive (free radical trapping) inhibition. In addition, there is evidence that NSAIDs have a central antinociceptive mechanism of action that augments the peripheral effect. This may involve inhibition of central nervous system prostaglandins or inhibition of excitatory amino acids or bradykinins. There is considerable variability in the pain relief obtained from NSAIDs. Such variability in drug response may be explained in terms of differences between agents with respect to either pharmacodynamic actions or pharmacokinetic parameters or a combination of both. Stereoisomerism, where preparations exist as racemic mixtures and where only 1 enantiomer is active, may also be important. However, chiral inversion from inactive to active enantiomer may occur and may be rapid or slow. NSAIDs have numerous adverse effects. Gastrointestinal disturbances including ulceration are the commonest adverse responses to NSAIDs and carry the greatest risk of death. Also significant are renal impairment and an increased risk of postoperative haemorrhage. Asthma and allergic reactions are uncommon.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-steroidal anti-inflammatory drugs and spinal nociceptive processing

Non-steroidal anti-inflammatory drugs have a direct action on spinal nociceptive processing in vivo with a relative order of potency which correlates with their capacity as inhibitors of cyclooxygenase activity. However, recent clinical surveys and new in vivo evidence strongly suggest that for some of these agents, centrally mediated analgesia may also be achieved by additional mechanisms, which are independent of prostaglandin synthesis inhibition. In this review we explore the likelihood for such mechanisms following an extensive survey of existing data. The implications of these mechanisms are discussed in the light of our current understanding of spinal nociceptive processing.

The use of third molar surgery in clinical pharmacology

This review discusses the various sequelae that arise after third molar surgery and their use for assessing the efficacy of a variety of therapeutic measures. The surgical procedure provides an opportunity to investigate onset, depth, duration and possible systemic effects of local anaesthetic solutions. Also, the anxiety which often accompanies such surgery lends itself to the appraisal of different anxiolytic agents and sedation techniques. The immediate postoperative sequelae of pain, buccal swelling and trismus provides a useful clinical model for evaluating the efficacy of analgesics and anti-inflammatory drugs. Third molar tooth sockets are susceptible to infection and this propensity enables the assessment of different antibiotic regimens. A further advantage of the third molar model is its application for crossover studies, with the patient acting as their own control. Very few surgical procedures afford this facility, which further adds to the value of this model in clinical pharmacology.

A double-blind comparative study of soluble aspirin and diclofenac dispersible in the control of postextraction pain after removal of impacted third molars

The analgesic efficacy and patient acceptability of soluble aspirin and diclofenac dispersible were compared in patients with postoperative pain after removal of impacted third molars. A total of 136 patients were randomly allocated to receive soluble aspirin 600 mg tds or diclofenac dispersible 50 mg tds after extraction under local anaesthesia of impacted third molars on one side of the mouth. The medication, which was both patient and operator blind, was reversed after extraction of the contralateral third molars 3 weeks later, the patients acting as their own controls in assessing postoperative pain, pain relief, and interincisal opening. Patients receiving diclofenac dispersible recorded significantly lower pain levels; pain relief was significantly greater and the patients' assessment significantly favoured diclofenac dispersible. Interincisal opening throughout the study period was significantly increased in the diclofenac dispersible group. The surgeons' postoperative assessment of extraction sites showed no significant difference between the two treatment groups in rate of healing. Two patients reported side-effects while taking soluble aspirin, and eight while taking diclofenac dispersible, two of whom discontinued treatment.

An evaluation of buffered aspirin and aspirin tablets in postoperative pain after third molar surgery

1. Single doses (500 and 1000 mg) of both buffered aspirin and aspirin tablets were compared with placebo in a randomised double-blind trial of parallel design in patients with postoperative pain after third molar surgery. 2. Only buffered aspirin 500 mg provided significant pain relief (P = 0.016) during the 5 h investigation period. 3. A significant correlation (P = 0.004) was observed between overall pain scores after the various aspirin treatments and aspirin esterase activity. 4. Buffered aspirin preparations afforded a slight advantage over aspirin tablets in the control of postoperative pain after third molar surgery. However, the duration of analgesia was short (approximately 2 h). 5. Aspirin esterase activity appears to be an important determinant of the drug's efficacy in postoperative dental pain.

Aspirin-induced decline in prostacyclin production in patients with coronary artery disease is due to decreased endoperoxide shift. Analysis of the effects of a combination of aspirin and n-3 fatty acids on the eicosanoid profile

BACKGROUND

It was the purpose of this study to determine the effects of the combination of aspirin (ASA) and fish oil, which is rich in n-3 polyunsaturated fatty acids, on the eicosanoid profile of patients with coronary artery disease. Specifically, we wanted to determine whether the ASA-induced reduction in prostacyclin production is due to inhibition of endothelial cell cyclooxygenase or to reduced endoperoxide shift from platelets and whether ASA negates the potentially beneficial effects of fish oil on the eicosanoid profile.

METHODS AND RESULTS

Fourteen patients with clinically stable but advanced coronary artery disease received 12 g (n = 8) or 16 g (n = 6) of fish oil concentrate containing 6 or 8 g of n-3 fatty acids for 6 weeks. In addition to the fish oil, patients received increasing daily doses of ASA (50 mg, 100 mg, 325 mg, and 1,300 mg; the latter in four divided doses). Each dose was taken for 2 weeks. With fish oil supplementation, red blood cell phospholipid fatty acid content of arachidonic acid (AA) decreased and of eicosapentaenoic acid (EPA) increased so that EPA as a percent of AA increased from 2% to 26%. Serum thromboxane B2, which represents the production of TXA2 by maximally stimulated platelets, was suppressed by 38% on fish oil alone and by 97% or greater on all doses of ASA. Excretion of PGI2-M, the main urinary metabolite of PGI2 (derived from AA), fell from 50 +/- 4 ng/g of creatinine to 42 +/- 2 ng/g on fish oil alone (p = 0.02). On 50 mg of ASA per day, PGI2-M excretion was 26 +/- 2 ng/g of creatinine (p less than 0.001 versus fish oil alone). On 100 mg and 325 mg of ASA per day, PGI2-M was 24 +/- 3 ng/g and 27 +/- 3 ng/g, respectively (p V NS versus value on 50 mg per day). PGI3-M, the main urinary metabolite of PGI3 (derived from EPA), increased from 0.2 +/- 0.1 ng/g of creatinine to 4.9 +/- 0.7 ng/g on fish oil alone (p less than 0.001). In contrast with the marked ASA-induced decline in PGI2-M, PGI3-M excretion was not affected by the addition of ASA, even at the higher doses (4.6 +/- 0.7 ng/g and 4.9 +/- 0.5 ng/g on 325 mg per day and 325 mg four times daily, respectively).

CONCLUSIONS

Moderate-dose (325 mg per day or less) ASA taken once daily has no effect on PGI3 production despite significantly reducing PGI2 production. This suggests that endothelial cell cyclooxygenase is minimally inhibited by such doses of ASA and that a large percent of the PGI2 produced in patients with advanced coronary artery disease derives from the transfer of prostaglandin endoperoxides from activated platelets to endothelial cells. The loss of these substrates accounts for the decrease in PGI2 with moderate-dose ASA. Thus, the ASA-induced decrease in PGI2 may in large part be an unavoidable consequence of ASA-induced platelet cyclooxygenase inhibition. ASA does not negate the potentially beneficial effects of n-3 fatty acids on the eicosanoid profile.

A study of the comparative efficacy of four common analgesics in the control of postsurgical dental pain

Four common oral analgesics were tested in a single-blind trial to determine their relative efficacy in the management of postsurgical pain in 103 patients who had their impacted third molars surgically removed under general anesthesia. The analgesics tested were acetylsalicylic acid (26 patients), ibuprofen (26 patients), a paracetamol/codeine/caffeine combination (Solpadeine) (25 patients), and dihydrocodeine (26 patients). The paracetamol/codeine/caffeine combination, ibuprofen, and acetylsalicylic acid preparations produced equally effective analgesia. Dihydrocodeine was found to be a poor analgesic in this pain model. There were no adverse reactions to any of the preparations.

Differential effect of aspirin on thromboxane and prostaglandin biosynthesis in man

1. Effects of a single intravenous dose of aspirin (600 mg) on bradykinin-stimulated prostaglandin (PG) and on thromboxane (TX) biosynthesis were determined in nine healthy male volunteers. Plasma concentrations of 6-oxo-PGF1 alpha and 13,14-dihydro-15-oxo-PGF2 alpha were measured in samples obtained during repeated 10 min intravenous infusions of bradykinin before and up to 6 h after the dose of aspirin. TXB2 was measured in serum from blood allowed to clot at 37 degrees C. 2. Aspirin inhibited bradykinin stimulated PG and platelet TX biosynthesis 0.5 h after the dose. Serum TXB2 remained low, whereas PG synthesis recovered within 6 h. 3. Effects of intravenous sodium salicylate (600 mg) were studied identically in eight subjects. Prostanoid biosynthesis was not inhibited. 4. Biosynthesis of prostacyclin and TXA2 under basal conditions was studied in eight subjects by measuring 2,3-dinor-6-oxo-PGF1 alpha and 2,3-dinor-TXB2 in hourly urine samples obtained during and after intravenous infusion of aspirin and, on a separate occasion, of vehicle. 5. Aspirin infusion reduced urinary excretion of both metabolites greater than 90%, but excretion of 2,3-dinor-6-oxo-PGF1 alpha recovered more rapidly than did that of 2,3-dinor-TXB2. 6. We conclude that cyclo-oxygenase is rapidly synthesised in bradykinin-responsive tissues in vivo and that this reflects similarly rapid enzyme biosynthesis in tissues that produce PGI2 under basal conditions.

An evaluation of different doses of soluble aspirin and aspirin tablets in postoperative dental pain

1. The efficacy of three different single doses (600, 900 and 1200 mg of soluble aspirin and aspirin tablets) was determined in a randomized placebo-controlled parallel study in 140 patients (70 females) with postoperative pain after removal of impacted third molars. 2. Patients treated with soluble aspirin 600 mg, 900 mg, 1200 mg and aspirin tablet 1200 mg reported significantly less pain (P less than 0.01) throughout the investigation period than those treated with placebo. 3. Overall pain scores after treatment with aspirin tablets 600 and 900 mg did not differ significantly from those after treatment with placebo (P greater than 0.05). 4. On a comparative dose basis, soluble aspirin was significantly more potent (P less than 0.05) than aspirin tablets.

Measurement of the analgesic effects of aspirin with a new experimental algesimetric procedure

Using controlled long lasting noxious squeeze stimuli applied to the interdigital webs we have tried to develop experimental methods allowing us to measure the effects of peripherally acting analgesics. In the present double-blind cross-over study with 12 subjects we tested the effects of aspirin (1000 and 1500 mg) vs. placebo on subjective pain induced by alternately applied 12 N (Newton) and 8 N stimuli. During the sessions blood samples were taken in regular intervals to measure acetylsalicylate (ASA)- and salicylate (SA)-plasma levels. Analyses of variance were computed with several psychophysical parameters. Both the '12 N' and the '8 N' ratings discriminated between placebo and aspirin, however, only the ratings obtained from the stronger stimuli discriminated between two doses of aspirin. Subsequently we computed analyses of covariance with the ASA- and SA-plasma levels as covariates. Significant (negative) correlations of pain ratings and SA-plasma levels were found for the high dose of aspirin, but there were no significant correlations of ASA levels and ratings.

Evaluation of low-intensity transcutaneous electrical nerve stimulation in combination with aspirin for reduction of controlled thermal sensation

Reductions in cutaneous thermal sensation produced by placebo, aspirin, transcutaneous electrical nerve stimulation, and transcutaneous electrical nerve stimulation plus aspirin were compared in 60 normal volunteers. The combination of transcutaneous electrical nerve stimulation plus aspirin produced a statistically significant reduction as compared with placebo. The results suggest this treatment combination may provide levels of analgesia useful for completion of minor dental procedures.

The antialgesic drugs: human therapeutic correlates of their potency in laboratory animal models of hyperalgesia

This survey discusses the correlation between the oral potency of antialgesic drugs in several pharmacology laboratories and their human oral dose in clinical practice. We also present a brief overview of a few biological assays that have been successfully used to direct the synthesis of newer antialgesic drugs. The laboratory assay that our analysis showed to be most predictive of the clinical analgesic dose is based upon the response of rats to flexion of an arthritic joint. Laboratory ED50 values from the ACh-induced abdominal constriction assay in mice are nearly as predictive while the predictive power of the yeast-induced hyperalgesia assay in rats is somewhat less. Probably because of the small number of experiments, the correlation between the efficacy of these agents in a canine model of synovitis and their clinical doses only reached borderline statistical significance (p = 0.0651). Regression equations are presented that permit calculations of single clinical analgesic doses from efficacy data in individual tests. Calculation of stepwise multiple regression showed that the clinical dose could be best predicted when efficacy data obtained in the joint flexion assay in rats and the ACh-induced constriction assay in mice are both taken into account. We have concluded that the effective doses are highly predictive of clinical efficacy because these animal assays have been designed to reflect the action of drugs upon prostanoid-induced hyperalgesia.

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.

Comparative efficacy of soluble aspirin and aspirin tablets in postoperative dental pain

The efficacy of single doses (1.2 g) of soluble aspirin and aspirin tablets was determined in a randomised, placebo-controlled, double-blind, parallel study in 90 patients (45 females) with postoperative pain after removal of impacted lower third molars. Also investigated was the relationship between plasma aspirin esterase activity and overall pain scores after both aspirin preparations. Patients reported significantly less pain (p less than 0.001) after treatment with aspirin than after treatment with placebo. However, patients receiving soluble aspirin reported both an earlier onset and a longer duration of pain relief than those who received aspirin tablets. A significant correlation was observed between plasma aspirin esterase activity and overall pain scores after both soluble aspirin (r = 0.57, p less than 0.01) and aspirin tablets (r = 0.51, p less than 0.02). It is concluded that soluble aspirin is the preferred aspirin formulation for treating postoperative pain after third molar surgery and that plasma aspirin esterase activity is determinant of a patient's analgesic response to aspirin in postoperative dental pain.

Aspirin and related derivatives of salicylic acid

After almost 90 years of clinical use, aspirin remains one of the world's most extensively used 'over-the-counter' drugs, and it is still recognised as the standard analgesic/antipyretic/anti-inflammatory agent by which newer drugs are assessed. However, its pre-eminent position as the analgesic of choice for mild to moderate pain has been seriously challenged with the introduction of many 'new' non-steroidal non-narcotic analgesic drugs. Indeed, there is convincing scientific evidence that many of the 'newer' non-steroidal drugs such as diflunisal, ibuprofen, flurbiprofen etc. are significantly superior analgesics and, in many cases, have a longer duration of action. In recent years the salicylates, aspirin in particular, have been the focus of much attention regarding their side effect profiles. At usual dosages for relief of pain and during occasional use, aspirin is well tolerated by the vast majority of patients. Adverse reactions, of which there is a wide spectrum, most frequently accompany anti-inflammatory doses of aspirin, or may be the result of accidental overdosing (particularly in children and the elderly)--probably a reflection of the lay population's acceptability of aspirin's presumed safety. As with other non-steroidal analgesic drugs, gastrointestinal complaints are the most commonly reported side effects. The existence of many shared clinical, adverse and toxic effects of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) is thought to be accounted for by a common mechanism--inhibition of the ubiquitous cyclo-oxygenase enzyme. Thus, suppression of prostaglandin biosynthesis is widely considered to explain the common properties of NSAIDS, although further research is still necessary to clarify some inconsistencies and to complete our understanding of the processes involved. Aspirin and salicylates have been reported to have a wide range of drug interactions but only relatively few seem to be clinically important. Many of the interactions are pharmacokinetic in nature. Drugs considered to produce the most significant interactions with salicylates include anticoagulants and thrombolytic agents, uricosuric agents, corticosteroids, methotrexate and sulphonylurea hypoglycaemic agents.

An investigation into post-operative pain after third molar surgery under local analgesia

The pain experienced after third molar surgery was investigated over a 7 day post-operative period in 80 patients. The results from the study suggest that post-operative pain is of short duration and reaches its maximum intensity in the early post-operative period. Nearly all patients required an analgesic at some time during the 7 days. The sex of the patient and whether there is a previous history of pericoronitis are important determinants of post-operative pain. However, the magnitude of post-operative pain does not appear to be dependent upon the operator or related to the extent of surgical trauma as assessed by operating time and radiographic score.

Aspirin causes short-lived inhibition of bradykinin-stimulated prostacyclin production in man

Acetylsalicylic acid (aspirin) inhibits prostanoid synthesis by irreversible acetylation of fatty acid cyclooxygenase (EC 1.14.99.1). It thereby inhibits synthesis of pro-aggregatory thromboxane A2 (TXA2) by platelets and is widely used in the treatment and prophylaxis of vascular disease. Its efficacy, however, may be reduced since it also inhibits formation of prostacyclin (PGI2) which is a vasodilator and anti-aggregatory agent. There is uncertainty over the optimum dose regimen for aspirin since although it inhibits platelet thromboxane production for many days, the magnitude and duration of its effect on PGI2 production by vascular endothelium in vivo is unknown. Resting plasma concentrations of PGI2 (measured as the stable hydrolysis product 6-oxo-PGF1 alpha) are at or below the limit of sensitivity of the most sensitive assays and cannot therefore be used to demonstrate a reduction in production. Bradykinin stimulates PGI2 synthesis by cultured human vascular endothelial cells and we have shown that it stimulates PGI2 production by man in vivo. We report here that an oral dose of aspirin (600 mg) causes rapid and substantial inhibition of bradykinin-stimulated PGI2 production, but recovery occurs within 6 hours; this implies that endothelial PGI2 synthesis would be spared most of the time during dosing once daily with even this relatively large dose of aspirin.

Clinical significance of esterases in man

Esterases, hydrolases which split ester bonds, hydrolyse a number of compounds used as drugs in humans. The enzymes involved are classified broadly as cholinesterases (including acetylcholinesterase), carboxylesterases, and arylesterases, but apart from acetylcholinesterase, their biological function is unknown. The acetylcholinesterase present in nerve endings involved in neurotransmission is inhibited by anticholinesterase drugs, e.g. neostigmine, and by organophosphorous compounds (mainly insecticides). Cholinesterases are primarily involved in drug hydrolysis in the plasma, arylesterases in the plasma and red blood cells, and carboxylesterases in the liver, gut and other tissues. The esterases exhibit specificities for certain substrates and inhibitors but a drug is often hydrolysed by more than one esterase at different sites. Aspirin (acetylsalicylic acid), for example, is hydrolysed to salicylate by carboxylesterases in the liver during the first-pass. Only 60% of an oral dose reaches the systemic circulation where it is hydrolysed by plasma cholinesterases and albumin and red blood cell arylesterases. Thus, the concentration of aspirin relative to salicylate in the circulation may be affected by individual variation in esterase levels and the relative roles of the different esterases, and this may influence the overall pharmacological effect. Other drugs have been less extensively investigated than aspirin and these include heroin (diacetylmorphine), suxamethonium (succinylcholine), clofibrate, carbimazole, procaine and other local anaesthetics. Ester prodrugs are widely used to improve absorption of drugs and in depot preparations. The active drug is released by hydrolysis by tissue carboxylesterases. Individual differences in esterase activity may be genetically determined, as is the case with atypical cholinesterases and the polymorphic distribution of serum paraoxonase and red blood cell esterase D. Disease states may also alter esterase activity.

Pain control after third molar surgery

The ideal agent for use after third molar surgery should alleviate pain, reduce swelling and trismus to a minimum, promote healing and have no unwanted effects. Of course, such an agent does not exist. For relief of pain, analgesics are the obvious choice. Where possible, an analgesic with additional anti-inflammatory properties should be used. There seems little to choose between aspirin, 1000 mg; diflunisal, 500 mg; ibuprofen, 400 mg and zomepirac sodium, 50 mg. In the subject allergic to aspirin and aspirin-like compounds, then paracetamol is the poor alternative. Surprisingly, the efficacy of most of the opioids in post-operative third molar pain is poor, and these drugs alone cannot be recommended for this purpose. Long-acting local anaesthetic solutions may be of value in some situations where extreme pain is likely to be a feature in the immediate post-operative period. However, there are no strict criteria for identifying such cases pre-operatively. Recent work on the use of corticosteroids would suggest that these drugs may be of value in reducing post-operative sequelae. Their future in dentistry in this rôle appears interesting and promising, and worthy of further study. Antihistamines and enzymes have been shown to be of little value, and the fact that these agents now receive little attention is evidence in its own right. The use of locally applied antimicrobials has been shown to be of little value in third molar surgery. In any case, their use is probably contraindicated because of the risk of sensitising the patient. The studies reviewed have not pointed to the effectiveness of the routine use of systemic antimicrobials in preventing or reducing postoperative sequelae after removal of impacted third molars in normal circumstances. Particular conditions, for example in patients susceptible to infection, may benefit by the use of prophylactic antimicrobials. However, each case must be judged on its individual merits, bearing in mind the attendant risks inherent in antimicrobial therapy. Finally, whatever agent is chosen for the control of the post-operative sequelae after third molar surgery, it must be borne in mind that, if the normal post-operative course occurs, then treatment is unlikely to extend beyond 48 h. Few doses of the particular agent will hence be used during this time period and thus the incidence of unwanted effects will be minimised.

Use of analgesics in postoperative dental pain: a review

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Rapid and sensitive determination of acetylsalicylic acid and its metabolites using reversed-phase high-performance liquid chromatography

A rapid and sensitive high-performance liquid chromatographic technique was developed for the simultaneous determination of gentisic acid, salicyluric acid, acetylsalicylic acid and salicylic acid in plasma and serum. The method involved a single deproteinization step and separation using a reversed-phase column eluted with a buffered methanol (35%) mobile phase. Detection was achieved with a variable-wavelength ultraviolet detector set at 235 nm and a given chromatographic analysis could be completed in less than 10 min. The method was tested in both human and animal (rat) models given a single dose of acetylsalicylic acid.

Aspirin metabolism and efficacy in postoperative dental pain

Aspirin 1200 mg was compared with placebo in a randomised, double-blind, crossover study in 15 patients with postoperative pain after removal of impacted lower third molars. Over a 5 h investigation period, patients reported significantly less pain (P less than 0.01) after treatment with aspirin, than after treatment with placebo. Peak concentrations of aspirin occurred at 15 min after dosage. Significant negative correlations were observed between plasma aspirin esterase activity and both AUC aspirin (r = -0.904, P less than 0.001) and AUC analgesia (r = -0.91, P less than 0.001). Similarly, a significant correlation was observed between AUC aspirin and AUC analgesia (r = 0.96, P less than 0.001). Evidence from this study would suggest that an individual's pain relief in postoperative dental pain is determined by the rate of aspirin hydrolysis to salicylate.

The efficacy and pharmacokinetics of sodium salicylate in post-operative dental pain

Sodium salicylate, 537 mg and 1074 mg were compared in a double-blind cross-over study in 24 patients with post-operative pain following removal of impacted lower third molars. No significant analgesic effect was observed after either dose of sodium salicylate, either overall or at any time point during the 5 h investigation period. Peak plasma concentrations of salicylate after 537 mg were observed at 30 min after dosage, whereas peak plasma salicylate concentrations after 1074 mg sodium salicylate occurred at 45 min after dosage.

Post-operative dental pain and analgesic efficacy. Part II. Analgesic usage and efficacy after dental surgery

The analgesics taken by patients after oral and periodontal surgery were noted over a three day observation period. Analgesic consumption matched closely the pain experience. The efficacy of self-prescribed analgesics was extrapolated from the pain scores obtained in the first 12 hours after surgery, and overall, the apparent efficacy appears poor. However, those patients who reported taking aspirin recorded significantly less pain than those who took either paracetamol or combination analgesics. Analgesic efficacy was not related to dose, although a significant correlation was noted between the number of paracetamol tablets taken and pain severity.

The use of pain scales in assessing the efficacy of analgesics in post-operative dental pain

Two 10 cm visual analogue scales were compared with a 0-10 point numerical rating scale and a four-point verbal descriptive scale, in assessing pain severity in twelve patients with post-operative pain following removal of an impacted lower third molar. High correlations were shown between the pain scores from the two visual analogue scales and the numerical scale, but a lower correlation was obtained when the four-point scale was compared with the other scales. Analgesic efficacy was found to be dependent on the type of scale used. The 10 cm visual analogue scale was more sensitive than other pain scales and could discriminate between small changes in pain intensity.