Review of the comparative analgesic efficacy of salicylates, acetaminophen, and pyrazolones

Efficacy and gastrointestinal risk of aspirin used for the treatment of pain and cold

AIMS

To analyse major sources of evidence-based information on the efficacy and gastrointestinal tolerability of aspirin, used short-term, in over-the-counter (OTC) doses, to relieve acute pain and cold symptoms, including associated feverishness.

METHODS

Evidence was largely collected from published meta-analyses and systematic reviews that focused on randomised, controlled, double-blind clinical trials, in which aspirin was compared to placebo and, in some cases also, to active comparators such as OTC doses of paracetamol or ibuprofen.

RESULTS

Across a large number of comparisons, aspirin was superior to placebo in treating pain, cold or fever. Efficacy was essentially similar to that of comparators used in equivalent doses. There was no serious GI adverse event attributed to ASA in any study, but mild-to-moderate dyspepsia in small percentages of cases was commonly reported.

CONCLUSION

OTC aspirin is safe and effective. Safety concerns should not limit brief use to relieve acute pain, cold or fever.

2-Phenyl-5-(trifluoro-meth-yl)pyrazol-3(2H)-one

The title compound, C(10)H(7)F(3)N(2)O, is an analogue of pyrazolone derivatives with potential analgesic and anti-inflammatory properties. Its mol-ecular structure consists of phenyl and pyrazol-3(2H)-one units with a dihedral angle between the mean planes of the rings of 33.0 (1)°. The crystal structure is stabilized by an inter-molecular hydrogen bond between the N-H group and the carbonyl O atom of the pyrazol-3(2H)-one ring which links the mol-ecules into supra-molecular C(5) chains along [001] and by weak π-π stacking inter-actions between the phenyl rings [centroid-centroid distance = 3.881 (2) Å]. The F atoms are disordered over two positions with refined site occupancies of 0.768(11) and 0.232(11).

Naproxen 500 mg bid versus acetaminophen 1000 mg qid: effect on swelling and other acute postoperative events after bilateral third molar surgery

A controlled, randomized, double-blind crossover study, in which the patients acted as their own controls, was carried out to test the efficacy of naproxen 500 mg x 2 versus acetaminophen 1000 mg x 4 for 3 days on the postoperative course following third molar surgery. Acetaminophen reduced the mean swelling on the 3rd postoperative day by 22.4% (p = 0.023) compared to that after naproxen. On the 6th postoperative day, there was 20.9% less mean swelling with naproxen (p = 0.44), although the total swelling measurements were much less than those measured on the 3rd postoperative day. Summed pain intensity (SUMPI3.5-11) on the day of surgery revealed no statistically significant difference between the acetaminophen or naproxen regimen with the exception of 0.5 hours (p = 0.002) and 1 hour (p = 0.009) after first medication when acetaminophen gave less pain than naproxen. Since the drug regimens were different, summed PI for the first acetaminophen dose interval (SUMPI3.5-6) and the first naproxen dose interval (SUMPI3.5-9) was calculated. There was a tendency toward a statistically significant difference in favor of acetaminophen for SUMPI3.5-6 (p = 0.055) but no statistically significant difference (p = 0.41) between the treatments with respect to SUMPI3.5-9. Naproxen was statistically superior (p < or = 0.002) to acetaminophen at 08:00, 12:00, and 16:00 hours on the 1st postoperative day and at 08:00 hours on the 2nd postoperative day, when the pain intensity level was lower than that on the day of surgery. A 3-day acetaminophen regimen reduces acute postoperative swelling better than naproxen on the 3rd postoperative day after third molar surgery but not on the 6th postoperative day when the total swelling is less.

Aspirin or acetaminophen? A comparison from data collected by the Spanish Drug Monitoring System

To characterize and compare the toxicity profiles of aspirin and acetaminophen when used by large populations, all records of adverse drug reactions to these drugs reported to the Spanish Drug Monitoring System from 1982 to 1991 were analyzed. According to these data, aspirin-induced reactions were more serious than those reactions to acetaminophen; the severity of all the reactions in both cases was associated with time of exposure and with the accumulated dose administered. For GI reactions to aspirin no association was found between severity and time of exposure or dose, although an association with age was found. There were no differences between the proportions of deaths, malformations, and renal damage recorded for either of the two groups. Proportions of hematological and hepatic disturbances were greater with acetaminophen. Adverse drug reaction data for aspirin and acetaminophen from spontaneous reporting seem to be consistent with data coming from observational studies.

Multicenter clinical trial of ibuprofen and acetaminophen in the treatment of postoperative dental pain

Pharmacological management of pain for acute and chronic conditions has been guided by a scientific understanding of peripheral and central acting mechanisms for the control of inflammation as well as pain. Oral surgery pain is a reliable model to reference the effectiveness of commonly used analgesics such as ibuprofen and acetaminophen. A total of 706 patients who were experiencing moderate to severe pain received a single dose of ibuprofen, acetaminophen, or placebo. After 6 hours, the degree of pain relief and tolerance was assessed. Ibuprofen has important implications for postoperative pain in clinical practice.

Paracetamol and phenacetin

Since their synthesis in the late 1800s paracetamol (acetaminophen) and phenacetin have followed divergent pathways with regard to their popularity as mild analgesic/antipyretic drugs. Initially, paracetamol was discarded in favour of phenacetin because the latter drug was supposedly less toxic. Today the opposite is true, and paracetamol, along with aspirin, has become one of the two most popular 'over-the-counter' non-narcotic analgesic agents. This marked increase in the wide approval attained by paracetamol has been accompanied by the virtual commercial demise of phenacetin because of its role, albeit somewhat circumstantial, in causing analgesic nephropathy. Both paracetamol and phenacetin are effective mild analgesics, suitable for treating mild to moderate pain, and their actions are broadly comparable with those of aspirin and related salicylates, although they do not appear to possess significant anti-inflammatory activity. Since a major portion of a dose of phenacetin is rapidly metabolised to paracetamol, it seems possible that phenacetin owes some of its therapeutic activity to its main metabolite, paracetamol, whereas its most troublesome side effect (methaemoglobinaemia) is due to another metabolite, p-phenetidine. The mechanism of action of paracetamol is poorly defined, although it has been speculated that it may selectively inhibit prostaglandin production in the central nervous system, which would account for its analgesic/antipyretic properties. The lack of any significant influence on peripheral cyclooxygenase would explain the absence of anti-inflammatory activity. At therapeutic doses paracetamol is well tolerated and produces fewer side effects than aspirin. The most frequently reported adverse effect associated with paracetamol is hepatotoxicity, which occurs after acute overdosage (usually doses greater than 10 to 15g are needed) and, very rarely, during long term treatment with doses at the higher levels of the therapeutic range. Paracetamol damages the liver through the formation of a highly reactive metabolite which is normally inactivated by conjugation with glutathione. Overdoses of paracetamol exhaust glutathione stores, thus allowing the accumulation of this toxic metabolite which covalently binds with vital cell elements and can result in liver necrosis. Glutathione precursors (notably intravenous N-acetylcysteine) have proved remarkably successful in treating paracetamol overdose, as long as treatment is initiated within 10 hours.(ABSTRACT TRUNCATED AT 400 WORDS)