Aspirin, paracetamol and non-steroidal anti-inflammatory drugs. A comparative review of side effects

The Role of Acupuncture in Relieving Post-Hemorrhoidectomy Pain: A Systematic Review of Randomized Controlled Trials

Background

Post-hemorrhoidectomy pain (PHP) remains one of the complications of hemorrhoidectomy and can delay patient's recovery. Current clinical guideline on PHP remains skeptical on the effectiveness of acupuncture, which has been applied for PHP in practice with inconsistent evidence.

Objectives

This systematic review aimed to evaluate the effectiveness of acupuncture on PHP by reviewing existing evidence.

Methods

Nine databases such as PubMed and Embase were searched for randomized controlled trials (RCTs) from inception to 30th September 2021. The outcome measures on pain level after hemorrhoidectomy, dose of rescue analgesic drug used, quality of life, adverse events, etc., were extracted and analyzed in a narrative approach.

Results

Four RCTs involving 275 patients were included in the analysis. One study showed that the visual analog scale (VAS) score was significantly lower in the electro-acupuncture (EA) group compared to that in the sham acupuncture (SA) group at 6, 24 h after surgery and during the first defecation (p < 0.05). Similar trends were found in the verbal rating scale (VRS) and Wong-Baker Faces scale (WBS) score but at different time points. Another study also found EA was effective on relieving pain during defecation up to 7 days after surgery when compared with local anesthetics (p < 0.05). However, two studies evaluating manual acupuncture (MA) compared with active medications for PHP showed inconsistent results on effectiveness. Variability was found in the quality of included studies.

Conclusions

Although benefit of acupuncture on PHP, especially EA on defecation after surgery, was observed at some time points, evidence on effectiveness of acupuncture on PHP was not conclusive.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, PROSPERO, identifier: CRD42018099961.

Indomethacin Enhances Type 1 Cannabinoid Receptor Signaling

In addition to its known actions as a non-selective cyclooxygenase (COX) 1 and 2 inhibitor, we hypothesized that indomethacin can act as an allosteric modulator of the type 1 cannabinoid receptor (CB1R) because of its shared structural features with the known allosteric modulators of CB1R. Indomethacin enhanced the binding of [³H]CP55940 to hCB1R and enhanced AEA-dependent [³⁵S]GTPγS binding to hCB1R in Chinese hamster ovary (CHO) cell membranes. Indomethacin (1 μM) also enhanced CP55940-dependent βarrestin1 recruitment, cAMP inhibition, ERK1/2 and PLCβ3 phosphorylation in HEK293A cells expressing hCB1R, but not in cells expressing hCB2R. Finally, indomethacin enhanced the magnitude and duration of CP55940-induced hypolocomotion, immobility, hypothermia, and anti-nociception in C57BL/6J mice. Together, these data support the hypothesis that indomethacin acted as a positive allosteric modulator of hCB1R. The identification of structural and functional features shared amongst allosteric modulators of CB1R may lead to the development of novel compounds designed for greater CB1R or COX selectivity and compounds designed to modulate both the prostaglandin and endocannabinoid systems.

Pattern of Prescribing NSAIDs Utilisation at Outpatient Pediatric Poly at Universitas Sumatera Utara Hospital

BACKGROUND:

The wrong prescription pattern on NSAIDs also often results in side effects and drug interactions that cause serious and detrimental drug reactions. Drug use research is needed to describe the pattern of drug use, early signs of rational drug use, interventions to improve drug use, cycles of quality control, and continuous quality improvement.

AIM:

This study aimed to determine the prescribing pattern of NSAIDs at outpatient Pediatric Poly at Universitas Sumatera Utara Hospital, Medan, Indonesia in 2017.

METHODS:

This descriptive retrospective study was conducted from October to November 2016 with data from July and August 2017.

RESULT:

The study showed, outpatient of pediatric poly at Universitas Sumatera Utara Hospital in Medan there were 45,000 prescriptions, and 62 (0.15%) prescriptions contained NSAIDs. The most frequently prescribed NSAIDs 53 (85.48%) of prescriptions for outpatient pediatric poly was paracetamol. The most use of NSAIDs was consumed by a female in the age group of 3 years-12 years was 35 (58.06%). The highest frequency of NSAIDs utilisation was 7 days with 25 prescriptions (40.32%). There were 17 (27.42%) prescriptions with inappropriate dose, and the most widely prescribed dosage form was syrup for 34 (54.83%) prescriptions. The most duration of treatment with NSAIDs drugs which is paracetamol reached up to seven-days 25 (40.32%). The most frequently prescribed drugs 57 (91.93%) were generic drugs.

CONCLUSION:

It can be concluded that there are still inappropriate doses and frequency of NSAIDs utilisation.

Effect of acupuncture on post-hemorrhoidectomy pain: a randomized controlled trial

Objectives

To observe the clinical efficacy and safety of electroacupuncture (EA) in relieving pain after hemorrhoidectomy treatment for mixed hemorrhoids.

Design

This was a randomized controlled trial.

Methods

We conducted a single-center, single-blind, and randomized controlled clinical trial. Seventy-two patients with mixed hemorrhoids who had undergone hemorrhoidectomy were randomly assigned to the following 2 groups: the EA treatment group (EA) received surround needling with EA (n=36), and the control group received sham acupuncture (SA) treatment (n=36). The treatment was conducted within 15 min after the completion of the surgery and lasted for 30 min. The pain intensity was recorded by using the visual analog scale as the primary outcome. Secondary outcomes were verbal rating scale and Wong-Baker Faces Pain Rating. These measurements were evaluated at 11 time points: once every hour in the first 8 h after the treatment, 24 and 48 h after the treatment, and at the first defecation. Besides, quality of life was measured by Symptom Checklist-90 Scale at 24 and 48 h follow-ups.

Results

The EA group had significantly lower visual analog scale scores at the 3 time points of 6, 24 h, and during the defecation (p<0.05). Verbal rating scale showed a significantly lower score in the treatment group compared to the SA group at 4 h after the treatment as well as during defecation (p<0.05). The Wong-Baker Faces Pain Rating scores of EA group were significantly lower at 5, 7, and 8 h after treatment and during defecation (p<0.05) compared with those of SA group.

Conclusion

Acupuncture is effective in alleviating postoperative pain in patients who have undergone hemorrhoidectomy.

COX-2 inhibition: what we learned--a controversial update on safety data

IMPORTANCE

Cyclooxygenase type 2 (COX-2)-selective nonsteroidal anti-inflammatory drugs (NSAIDs) (c2sNSAIDs) have been scrutinized relative to the less costly nonselective NSAIDs (nsNSAIDs). The conclusions reached were not always consistent with the data, and best treatment choices for patients were not always recommended.

OBJECTIVE

The data that were used to criticize the c2sNSAIDs are reexamined in a controversial light, demonstrating that the presence of reverse bias was often, but not always, present.

EVIDENCE REVIEW

A review of both Pubmed and news media articles relating to nsNSAIDs and c2sNSAIDs was conducted. References were selected on the basis of relevance to the controversies.

FINDINGS

The initial claims for the c2sNSAIDs of reduced gastrointestinal (GI) injury and preservation of platelet function were soon dwarfed by concerns regarding increased cardiovascular (CV) risk with publication of the Vioxx Gastrointestinal Outcomes Research trial for rofecoxib. Initial prothrombotic theories had a poor basis for explaining these concerns and have since largely been replaced with more credible explanations, including blood pressure elevations known to occur with all NSAIDs. Between data suggesting increased CV risk and under political pressure and public outcry, rofecoxib was withdrawn from the market in 2004. Soon, all c2sNSAIDs were under scrutiny. The Food and Drug Administration has since grouped all NSAIDs, whether c2sNSAID or nsNSAID, into one class with similar warnings regarding skin, CV, renal, and GI side effects.

CONCLUSIONS AND RELEVANCE

The entire "COX-2 debacle" is reminiscent of past events with NSAIDs. Amid this public, media, and political hysteria, it is not clear if we will see any more NSAIDs (selective or otherwise) approved in the near future.

A randomized, double-blind, 8-week crossover study of once-daily controlled-release tramadol versus immediate-release tramadol taken as needed for chronic noncancer pain

OBJECTIVE

The purpose of this study was to evaluate the efficacy of controlled-release (CR) tramadol and immediate-release (IR) tramadol in patients with moderate or greater intensity chronic noncancer pain.

METHODS

A total of 122 patients underwent washout from all opioids 2 to 7 days before randomization to 1 of 2 groups: active CR tramadol 200 mg every morning plus placebo IR tramadol 50 mg every 4 to 6 hours PRN rescue, or placebo CR tramadol 200 mg every morning plus active IR tramadol 50 mg every 4 to 6 hours PRN rescue. After 2 weeks, the doses were increased to CR tramadol 400 mg or placebo and IR tramadol 100 mg every 4 to 6 hours PRN or placebo, as rescue. After 4 weeks in the first phase, patients crossed over to the alternative treatment for another 4 weeks. Pain intensity (100-mm visual analog scale [VAS] and 5-point ordinal scales) was assessed twice daily in diaries. Pain intensity, Pain and Disability Index (PDI; 0-10 ordinal scale), Pain and Sleep Questionnaire (100-mm VAS), and analgesic effectiveness (7-point ordinal scale) were assessed at biweekly clinic visits.

RESULTS

Sixty-five patients (35 men, 30 women) completed the study. Mean (SD) age was 56.5 (12.7) years; mean (SD) weight was 82.0 (18.5) kg. Daily diary pain intensity (mean [SD]) was significantly lower in the CR tramadol group than in the IR tramadol group in the last 2 weeks of each phase (completers: VAS, 29.9 [20.5] vs 36.2 [20.4] mm, P < 0.001; ordinal scale, 1.41 [0.7] vs 1.64 [0.6], P < 0.001; intent-to-treat [ITT] population: VAS, 32.5 [22.9] vs 38.6 [21.2] mm, P < 0.003; ordinal scale, 1.50 [0.8] vs 1.72 [0.7], P < 0.002). The overall pain intensity scores from the daily diary were also significantly better with CR tramadol for both the completers and ITT. Similar results were obtained on the biweekly VAS pain intensity questionnaire. No differences were found between treatments in total PDI or overall Pain and Sleep scores in either population. For the completers, both patients and investigators rated effectiveness higher for CR tramadol than for IR tramadol (P < 0.004 and P < 0.008 for patients and investigators, respectively).

CONCLUSION

This study reports significant improvement in pain intensity with CR tramadol as compared with IR tramadol.

Pharmacologic therapies for neck pain

A variety of drug types are available for the treatment of pain. Significant relief of acute neck pain is usually achievable. Treatment of chronic neck pain requires a more comprehensive rehabilitation approach combined with judicious use of medications. Research on the development of analgesics that affect other neurotransmitter systems and that have fewer side effects is currently underway.

Treatment of acute low back pain with the COX-2-selective anti-inflammatory drug nimesulide: results of a randomized, double-blind comparative trial versus ibuprofen

STUDY DESIGN

A prospective, randomized double-blind comparative trial.

OBJECTIVES

To evaluate the efficacy and tolerability of nimesulide, a cyclooxygenase (COX)-2-selective anti-inflammatory agent versus ibuprofen in patients with acute lumbosacral back pain.

SUMMARY OF BACKGROUND DATA

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been more effective than placebo in patients with uncomplicated acute low back pain in previous randomized controlled trials. The efficacy and tolerability of a new COX-2-selective anti-inflammatory drug have not yet been established.

METHODS

One hundred four patients aged 18-65 years with acute low back pain were enrolled. The patients were randomly allocated either to oral nimesulide (100 mg twice daily for 10 days) or oral ibuprofen (600 mg three times daily for 10 days). Outcome measures on a visual analog scale were an average of the pain intensity and the pain relief, stiffness in the back, functional status, and the results of physical examinations. All side effects were recorded at each visit.

RESULTS

With both study therapies, there was a clear improvement in all measured parameters of the pain and back function parameters measured from the third day of treatment onward. The patients' capacity for daily tasks, showed improvement in both groups (P < 0. 001), but a statistically significant difference was found between the two groups in favor of the nimesulide group (P < 0.05) after 10 days. Nimesulide was more effective than ibuprofen in improved lateral bending measurements (P = 0.026). Nimesulide and ibuprofen provided similar degrees of improvement in the modified Schober tests and in the pain intensity and back stiffness scores. More gastrointestinal side effects were reported with ibuprofen than nimesulide, and the comparison showed a trend (P = 0.067). Ten side effects occurred in the nimesulide group in 7 (13%) patients and 13 in the ibuprofen group in 11 (21%) patients.

CONCLUSIONS

The results confirmed that the COX-2-selective inhibitor nimesulide is an effective and well-tolerated agent for use in general practices to treat acute low back pain. The incidence of gastrointestinal side effects seems to be lower with nimesulide than with ibuprofen.

Studies on the in vitro release characteristics of ibuprofen-loaded polystyrene microparticles

Ibuprofen-loaded polystyrene microparticles were prepared by the emulsion-solvent evaporation process from an aqueous system. The effects of different parameters on the drug content and on the release of the drug from the microparticles were investigated. The drug content, in all the formulations, was less than the theoretical drug loading. The lower drug content was due to drug partitioning to the external aqueous phase during formulation. Statistical analysis revealed that the variation in the concentrations of the emulsion stabilizer and the organic disperse phase volume did not significantly alter the release of the drug. Although an increase in drug loading increased drug release from the microparticles, a biphasic linear relationship was observed between the time required for 50% drug release and the drug loading. The effect of size of the microparticles on drug release was more important for the low drug-loaded microparticles than that for the high drug-loaded microparticles. Such release behaviour from the microparticles was explained on the basis of the morphological structure of the microparticles.

Digestive System 1

This chapter deals with the digestive system. The major and minor salivary glands and their secretions also represent and integral part of the protective mechanism of the oral cavity, and derangement of saliva production may lead to loss of integrity of the oral mucosa. Drug-induced abnormalities of taste sensation are also well-described phenomena occurring in man although human studies are necessary for the detection of these effects. Inflammation of the oral cavity may involve the buccal mucosa, the gingiva (gingivitis), the tongue (glossitis), and the peridontal tissues (peridontitis). Therapeutic agents can induce inflammatory lesions in the tongue. Moreover, a protective layer of mucus, a visco-elastic material containing high molecular weight glycoproteins produced by the major and minor salivary glands, covers the stratified squamous mucosa of the oral cavity. Salivary secretions also possess digestive enzyme activity although in herbivores and carnivores, it is usually low in contrast to high digestive enzyme activity in omnivorous species.

Medication use for low back pain in primary care

STUDY DESIGN

A longitudinal observational study of primary care patients with low back pain.

OBJECTIVES

1) To describe medications prescribed for back pain, 2) to identify patient characteristics associated with type of drug therapy, 3) to determine if the prescription of certain drugs is associated with better outcomes, and 4) to compare physician prescribing behavior with national guidelines.

SUMMARY OF BACKGROUND DATA

Few previous studies have focused on medication prescribing patterns for back pain in primary care.

METHODS

Two-hundred nineteen patients aged 20-69 years who were making a first visit for an episode of back pain were studied. After the visit, patients completed questionnaires regarding sociodemographic characteristics, health status, back pain experience, and use of medications. Symptom severity and dysfunction were assessed by telephone 1 week after the visit.

RESULTS

Sixty-nine percent of patients were prescribed nonsteroidal anti-inflammatory drugs, 35% muscle relaxants, 12% narcotics, and 4% acetaminophen. Twenty percent received no medications. Patients were more likely to receive medications if they had a desire for medication, pain below the knee, less than 3 weeks of pain before visit, more severe symptoms, or greater dysfunction. Patients with more severe symptoms were more likely to receive narcotics or muscle relaxants. Patients with greater dysfunction were also more likely to receive narcotics. Type of drug therapy predicted symptom severity but not dysfunction after 1 week. Controlling for other factors, those receiving medications had less severe symptoms after 1 week than patients who received no medication. Patients receiving both muscle relaxants and nonsteroidal anti-inflammatory drugs had the best outcomes. Medication use for back pain in this health maintenance organization was generally concordant with national guidelines.

CONCLUSIONS

Nonsteroidal anti-inflammatory drugs, often augmented by muscle relaxants, are a standard medical treatment for back pain in primary care. In this observational study, patients prescribed medications, particularly muscle relaxants, reported less severe symptoms after 1 week than those receiving no medications. However, randomized trials are needed to determine which medication or combinations of medications are most effective.

Adjunctive methods of pain control in burns

Opiates remain the most common form of analgesic therapy in the burn patient today. Because of increased opiate requirements, optimal relief of burn pain continues to be a problem for these patients. The purpose of this article is to summarize those alternative pain control methods that appear in the literature. For instance, in minor burns acetominophen continues to be a useful first line analgesic. Non-steroidal anti-inflammatory drugs (NSAID) and benzodiazepine are generally combined with opiates while entonox seems to be used commonly in the adolescent patients to relieve procedural pain. Antidepressants appear to enhance opiate-induced analgesia while anticonvulsants are useful in the treatment of sympathetically maintained pain following burns. Ketamine has been extensively used during burn dressing changes but its psychological side-effects have limited its use. Clonidine, however, has shown promise in reducing pain without causing pruritus or respiratory depression. Other forms such as transcutaneous electrical nerve stimulation (TENS), psychological techniques, topical and systemic local anaesthetics are also useful adjuncts.

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.

Development and use of a gastropathy index for ranking the safety of non-steroidal anti-inflammatory drugs in the elderly

This study, conducted at the Royal Devon & Exeter Hospital, Department of Geriatric Medicine, was carried out using 2987 sets of admission data. The number of patients taking non-steroidal anti-inflammatory drugs was identified together with a suite of clinical factors used to indicate the presence of gastrointestinal pathology. From this a gastropathy index was developed to establish a rank order for the individual drugs. Ketoprofen, piroxicam and fenbufen were all significantly associated with factors suggestive of gastropathy, whereas indomethacin, diclofenac and ibuprofen appeared relatively free of such association. Naproxen, azapropazone and mefenamic acid ranked in an intermediate category. This noninvasive analysis of routinely acquired data provides a potentially useful discriminator between individual non-steroidal anti-inflammatory drugs for this age group.

Intraarticular injections of hyaluronan in patients with cartilage abnormalities and knee pain. A one-year double-blind, placebo-controlled study

OBJECTIVE

To compare the effect of intraarticular injections of hyaluronan and placebo (vehicle, saline) in patients with knee pain on exertion and with joint cartilage abnormalities.

METHODS

Fifty-two patients with arthroscopically verified deep cartilage fissures and villus-like flakes in the symptomatic knee were randomly assigned to receive intraarticular injections of 2.5 ml of either hyaluronan or vehicle, weekly for 5 weeks. The effect was evaluated by both primary and secondary parameters of efficacy at 2, 4, 13, 26, and 52 weeks.

RESULTS

At the followup visits, both groups had improvement from baseline; however, there was no difference between the groups in any of the relevant variables at any time point.

CONCLUSION

The effects of intraarticular hyaluronan do not differ significantly from those of placebo in patients with knee pain and cartilage disease.

Patterns of out-patients non-steroidal anti-inflammatory drug prescribing in two teaching hospital rheumatology units--implications for post-marketing surveillance

Patterns of prescriptions or recommendations for non-steroidal anti-inflammatory drugs (NSAIDs) were examined in the out-patient departments of two teaching hospital rheumatology units [The General Infirmary, Leeds (n = 140), and Musgrave Park Hospital, Belfast (n = 77)]. In both units four drugs accounted for over 80% of prescriptions/recommendations (diclofenac, indomethacin, ibuprofen and naproxen in Leeds and flurbiprofen, nabumetone, ibuprofen and diclofenac in Belfast). In Leeds patients with pre-existing upper gastrointestinal problems were more likely to receive diclofenac whereas in Belfast they were more likely to receive nabumetone or ibuprofen. In Leeds, patients who received indomethacin tended to be young males with seronegative arthritis. These differences between drugs and between centres could have important implications for cost, design and interpretation of studies of post-marketing surveillance.

Metamizole: reassessment of its therapeutic role

The use of metamizole is controversial, as reflected in the very different national regulations affecting it. The striking disparities between policies for metamizole made us try to determine if there were reasons to ban, limit or liberalize its utilization. After reviewing the literature, it was concluded that metamizole should not be withdrawn from the countries where its use is still relatively free. However, metamizole causes life-threatening adverse events that are usually unpredictable and can only be prevented by better prescribing habits, so it is suggested that its use as a first-line agent should be restricted to the treatment of the pain of acute colic and circumstances in which parenteral administration of a non-narcotic agent is mandatory. Studies are needed to determine the role of second-line oral analgesics in terms of their overall toxicity and efficacy. In the meantime it is proposed that oral metamizole should be used only when other analgesics (e.g. paracetamol) have failed.

Clinical pharmacology and use of nonsteroidal anti-inflammatory drugs

This review informs clinicians about current clinical usage and pharmacokinetics of newer NSAIDs and aspirin. To understand the effects of these drugs, a review of prostaglandin synthesis and actions is provided.

Pharmacologic management of pain in children and adolescents

In the management of chronic pain conditions, the combination of pharmacologic measures with physical and psychologic modalities becomes even more important. A pain clinic and pain consultation service are one model that facilitates this combined approach. Initial management of mild to moderate pain begins with nonopioid analgesics such as acetaminophen and NSAIDs. Persistent severe pain of a neuropathic character merits careful trials of antidepressants or anticonvulsants. Traditionally, use of opioids for chronic pain not due to cancer has been discouraged for adults as well as children. Recently, this view was challenged by reports by Portenoy and Foley and by Taub, who followed a group of adults with chronic pain due to a variety of conditions. They found that the majority of these patients, if managed with opioids on a regular schedule as part of an overall treatment program, could be made comfortable and were able to increase their level of functioning for several years. In general, dosage escalation and compulsive drug-seeking behaviors were not seen. Since this report was retrospective and did not involve children, caution must be applied in extrapolating these findings to children. For example, remarkably little is known about the effects of chronic opioid administration in childhood on growth and development. Certainly, this issue deserves further study before general recommendations can be made. It seems prudent to emphasize the importance of maximizing nonpharmacologic and nonopioid approaches in the management of chronic pain in children prior to embarking on long-term use of opioids.

Side-effects of non-steroidal anti-inflammatory drugs

Despite a continuing lack of good quality epidemiological studies, our knowledge of the side-effects of NSAIDs has advanced in recent years. The most important reactions are those which are related predictably to the pharmacology of the drugs and these need to be considered whenever a NSAID is prescribed, particularly for patients who can be identified as belonging to high-risk groups. The important reactions are: 1. Gastrointestinal damage, which is now known to extend to some degree from the oesophagus to the rectum, although the acid contact areas of the stomach and duodenum are the most important. Although the studies have produced heterogeneous results, NSAIDs probably double or triple the risk of an individual developing serious gastrointestinal haemorrhage or perforation. The risk increases with age and previous history of ulceration, and, in communities with particularly high use of NSAIDs, the drugs may account for up to 30% of all cases of ulcer complications. 2. Renal syndromes, of which functional renal impairment is the most important. This may precipitate cardiac failure, and hyperkalaemia is an additional hazard. Antagonism of the action of diuretics may contribute to the fluid retention, and antagonism of antihypertensive therapy is probably quite common and may result in additional unnecessary therapy. Patients at risk of functional renal impairment from NSAIDs can be identified readily and in these subjects the drugs have to be used with great care and with appropriate monitoring. 3. Respiratory effects, in particular acute bronchospasm in subjects with a history of aspirin sensitivity. NSAIDs should be used with caution in asthmatics, and patients purchasing NSAIDs without prescriptions need to be warned of these effects. Other uncommon serious reactions include hepatocellular damage, acute interstitial nephritis, agranulocytosis and aplastic anaemia, Stevens-Johnson syndrome and toxic epidermal necrolysis. These are unpredictable reactions which generally need not be considered before prescribing. However, in patients who present with any of these conditions, NSAIDs, because of their wide use, should always be considered as a possible cause.