The comparative effects of paracetamol and indomethacin on renal function in healthy female volunteers

Physiological confounders of renal blood flow measurement

OBJECTIVES

Renal blood flow (RBF) is controlled by a number of physiological factors that can contribute to the variability of its measurement. The purpose of this review is to assess the changes in RBF in response to a wide range of physiological confounders and derive practical recommendations on patient preparation and interpretation of RBF measurements with MRI.

METHODS

A comprehensive search was conducted to include articles reporting on physiological variations of renal perfusion, blood and/or plasma flow in healthy humans.

RESULTS

A total of 24 potential confounders were identified from the literature search and categorized into non-modifiable and modifiable factors. The non-modifiable factors include variables related to the demographics of a population (e.g. age, sex, and race) which cannot be manipulated but should be considered when interpreting RBF values between subjects. The modifiable factors include different activities (e.g. food/fluid intake, exercise training and medication use) that can be standardized in the study design. For each of the modifiable factors, evidence-based recommendations are provided to control for them in an RBF-measurement.

CONCLUSION

Future studies aiming to measure RBF are encouraged to follow a rigorous study design, that takes into account these recommendations for controlling the factors that can influence RBF results.

The Complexities of Interpreting Reversible Elevated Serum Creatinine Levels in Drug Development: Does a Correlation with Inhibition of Renal Transporters Exist?

In humans, creatinine is formed by a multistep process in liver and muscle and eliminated via the kidney by a combination of glomerular filtration and active transport. Based on current evidence, creatinine can be taken up into renal proximal tubule cells by the basolaterally localized organic cation transporter 2 (OCT2) and the organic anion transporter 2, and effluxed into the urine by the apically localized multidrug and toxin extrusion protein 1 (MATE1) and MATE2K. Drug-induced elevation of serum creatinine (SCr) and/or reduced creatinine renal clearance is routinely used as a marker for acute kidney injury. Interpretation of elevated SCr can be complex, because such increases can be reversible and explained by inhibition of renal transporters involved in active secretion of creatinine or other secondary factors, such as diet and disease state. Distinction between these possibilities is important from a drug development perspective, as increases in SCr can result in the termination of otherwise efficacious drug candidates. In this review, we discuss the challenges associated with using creatinine as a marker for kidney damage. Furthermore, to evaluate whether reversible changes in SCr can be predicted prospectively based on in vitro transporter inhibition data, an in-depth in vitro-in vivo correlation (IVIVC) analysis was conducted for 16 drugs with in-house and literature in vitro transporter inhibition data for OCT2, MATE1, and MATE2K, as well as total and unbound maximum plasma concentration (Cmax and Cmax,u) data measured in the clinic.

Characterization of Organic Anion Transporter 2 (SLC22A7): A Highly Efficient Transporter for Creatinine and Species-Dependent Renal Tubular Expression

The contribution of organic anion transporter OAT2 (SLC22A7) to the renal tubular secretion of creatinine and its exact localization in the kidney are reportedly controversial. In the present investigation, the transport of creatinine was assessed in human embryonic kidney (HEK) cells that stably expressed human OAT2 (OAT2-HEK) and isolated human renal proximal tubule cells (HRPTCs). The tubular localization of OAT2 in human, monkey, and rat kidney was characterized. The overexpression of OAT2 significantly enhanced the uptake of creatinine in OAT2-HEK cells. Under physiologic conditions (creatinine concentrations of 41.2 and 123.5 µM), the initial rate of OAT2-mediated creatinine transport was approximately 11-, 80-, and 80-fold higher than OCT2, multidrug and toxin extrusion protein (MATE)1, and MATE2K, respectively, resulting in approximately 37-, 1850-, and 80-fold increase of the intrinsic transport clearance when normalized to the transporter protein concentrations. Creatinine intracellular uptake and transcellular transport in HRPTCs were decreased in the presence of 50 µM bromosulfophthalein and 100 µM indomethacin, which inhibited OAT2 more potently than other known creatinine transporters, OCT2 and multidrug and toxin extrusion proteins MATE1 and MATE2K (IC50: 1.3 µM vs. > 100 µM and 2.1 µM vs. > 200 µM for bromosulfophthalein and indomethacin, respectively) Immunohistochemistry analysis showed that OAT2 protein was localized to both basolateral and apical membranes of human and cynomolgus monkey renal proximal tubules, but appeared only on the apical membrane of rat proximal tubules. Collectively, the findings revealed the important role of OAT2 in renal secretion and possible reabsorption of creatinine and suggested a molecular basis for potential species difference in the transporter handling of creatinine.

A systematic review of the effect of paracetamol on blood pressure in hypertensive and non-hypertensive subjects

AIM

To review current evidence on the effect of paracetamol on blood pressure (BP), the quality of the previous studies and the validity of the results, and to summarize these findings.

METHODS

A systematic literature review was performed by searching PubMed, the Cochrane library and EMBASE for publications between the years 1963 and 2012.

RESULTS

We identified three case reports, seven prospective observational trials, six randomized controlled trials, one commentary and two reviews. Some, but not all, of the observational studies, which included over 147 000 patients, showed an increased risk of hypertension with paracetamol use. The randomized studies were generally small and the results were inconsistent. Three studies, which included 104 patients, showed an increase of systolic BP by ~4 mmHg, two studies, which included 27 patients, reported no change in BP and one study, which included 21 patients, reported a fall in BP although no placebo arm was included for comparison.

CONCLUSIONS

The overall effect of paracetamol on BP is unclear. Given that paracetamol is often suggested as a safer alternative to non-steroidal anti-inflammatory drugs (NSAIDs), it would seem that further prospective evidence is now needed to address the effect of paracetamol on BP. This would be best done with larger studies in relevant cohorts using BP measured by ambulatory BP monitoring as the primary endpoint.

Drug Interactions with Paracetamol

Paracetamol (acetaminophen) is one of the most commonly used analgesic antipyretic drugs worldwide, and it is widely available by prescription and over the counter (OTC). Fortunately, few clinically significant drug interactions have been documented. There is probable potentiation of hepatotoxicity following an overdose from the paracetamol metabolite NAPQI by enzyme-inducing drugs. There is considerable controversy regarding the possible interaction with warfarin in its potential to increase its anticoagulant effects because of discrepancies between observational studies and those in healthy volunteers. Otherwise, no serious adverse drug interactions with therapeutic doses of paracetamol have been confirmed in humans. Because the absorption of paracetamol is so dependent on gastric emptying, other drugs that alter gastric emptying can change its pharmacokinetics; but this would not cause serious adverse effects. Although animal experiments have demonstrated that many compounds can modify paracetamol hepatotoxicity, these are unlikely to be important at therapeutic doses.

Cyclooxygenase-2 inhibitors and nonsteroidal anti-inflammatory drugs in the management of arthritis

The management of arthritis pain should be individualized to the needs and characteristics of the patient. The decision to use nonsteroidal anti-inflammatory drugs (NSAIDs), and in particular the cyclooxygenase-2 (COX-2) inhibitors, is multidimensional. The challenge is to achieve optimal pain relief at the minimum dose to minimize adverse effects. Whenever possible, NSAIDs should be given as monotherapies or in combinations at the lowest effective doses. The COX-2 inhibitors are a safe choice for most patients who are at low risk for a cardiovascular event. Individuals who are at risk for thromboses should not receive unopposed COX-2 inhibitors; COX-2 should be given in combination with low-dose aspirin which is expected to be cardioprotective in high-risk patients.

Determinants and sequelae associated with utilization of acetaminophen versus traditional nonsteroidal antiinflammatory drugs in an elderly population

OBJECTIVE

Acetaminophen is recommended as initial therapy for patients with arthritis, particularly those at increased risk of nonsteroidal antiinflammatory drug (NSAID)-induced gastrointestinal (GI) side effects. However, higher doses of acetaminophen inhibit prostaglandin synthesis and have been associated with GI events. This study was undertaken to compare the observed and adjusted rates of GI events (hospitalizations, ulcers, dyspepsia, GI prophylaxis) occurring with higher versus lower doses of acetaminophen.

METHODS

This was a retrospective cohort study of subjects ages >or=65 years who received a prescription for acetaminophen or NSAID between 1994 and 1996. Pharmaceutical and medical records were reviewed for 1 year of historical data prior to the index prescription of acetaminophen or non-aspirin NSAID. Risk factors for GI events were identified based on the historical data. To further control for bias, patients were categorized by propensity score (the likelihood of receiving acetaminophen, given defined risk factor values). Records were then reviewed for the duration of the index prescription or 30 days, whichever was less, to generate data on the occurrence of GI events. Determinants of acetaminophen utilization were identified using logistic regression, and rates of GI events for each therapy were examined using Poisson regression analyses, controlling for duration of exposure, individual risk factors, and propensity scores.

RESULTS

The study included 26,978 patients in the NSAID cohort and 21,207 in the acetaminophen cohort. Determinants of acetaminophen utilization compared with NSAIDs (odds ratio [95% confidence interval]) included recent hospitalization (8.6 [7.7-9.5]), concomitant anticoagulation therapy (3.2 [2.7-3.8]), age >85 years (2.3 [2.1-2.4]), and history of prior GI events, especially those requiring hospitalization (14.6 [11.7-18.7]). Unadjusted rates of GI hospitalization, ulcer, and dyspepsia were higher for patients in the acetaminophen cohort than for those in the NSAID cohort. The occurrence of GI events in acetaminophen-treated patients was dose dependent, with rate ratios (compared with high-dose NSAIDs and adjusted for risk susceptibility) ranging from 0.6 (95% confidence interval 0.5-0.7) for <or=650 mg/day to 1.0 (0.9-1.1) for >3,250 mg/day.

CONCLUSION

In this cohort, acetaminophen utilization is more common in patients at higher risk of GI events. After adjustment for risk susceptibility, patients receiving higher doses of acetaminophen have higher rates of GI events compared with those receiving lower doses.

Areas of emerging interest in analgesia: cardiovascular complications

Many people obtain symptomatic relief from acute, chronic, or recurring pain conditions by using an over-the-counter analgesic. As with the use of any drug, this involves achieving the appropriate balance between potential benefit and risk of harm. The adverse effects of aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) in the gastrointestinal (GI) tract are widely appreciated. On the basis of their pharmacology, however, these drugs also have the potential for causing adverse effects in the cardiovascular system. This is particularly the case in certain overlapping populations (eg, the elderly or those with cardiac failure, hypertension, or renal impairment). And the size of the exposed populations and the fact they comprise people likely to require pain management because of concomitant illnesses make the cardiovascular implications of analgesic use potentially a more serious issue for public health than the more widely recognized GI complications of aspirin and NSAID use. This article discusses the impact on the cardiovascular system of different classes of analgesics (NSAIDs, the new cyclooxygenase-2-selective inhibitors [CSIs], and paracetamol) in terms of cardiac function, thrombotic and cardioprotective potential, and hypertension. It identifies patients at risk for analgesic-related cardiovascular adverse events, and considers their options for managing mild-to-moderate pain. Unlike that of the NSAIDs and CSIs, the pharmacology of paracetamol provides no signal for risk of cardiovascular adverse events, and paracetamol should, therefore, be considered as first-line therapy in patients with cardiovascular disease.

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.

Effects of short-term use of ibuprofen or acetaminophen on bone resorption in healthy men: a double-blind, placebo-controlled pilot study

Prostaglandins are known to be involved in the metabolism of bone, having a significant influence on bone resorption in cases of bone pathology. We therefore investigated the short-term effects of two commonly used nonsteroidal anti-inflammatory drugs (NSAIDs), ibuprofen and acetaminophen (paracetamol), on bone resorption in healthy men. In a randomized, double-blind pilot study, 28 healthy, age- and weight-matched male volunteers were treated with ibuprofen (n = 10), acetaminophen (n = 9), or a placebo (n = 9) for 3 days. As an indication of bone resorption rate, levels of the biochemical bone markers N-telopeptide (NTx) and free deoxypyridinoline (D-Pyr) were measured in urine. Differences in resorption marker levels pre- and post-NSAID use were then compared between groups. We found that NTx concentrations in the acetaminophen group were lower than placebo (p = 0.048), whereas NTx levels in the ibuprofen group were higher than in the acetaminophen group (p = 0.016). By contrast, D-Pyr concentrations in the ibuprofen group were significantly lower than in the placebo group (p = 0.009). A comparison of the percentage changes of D-Pyr:NTx ratios found that the ratio in the ibuprofen group was significantly lower than that of both the control (p = 0.0065) and acetaminophen (p = 0.01) groups. These results show the differential effects of ibuprofen and acetaminophen on urinary excretion of peptide-bound and free deoxypyridinoline cross-links of type I collagen. Short-term ibuprofen use may alter the renal handling of collagen cross-links and increase bone resorption to a greater extent than acetaminophen in normal men.

Effects of acetaminophen and ibuprofen on renal function in anesthetized normal and sodium-depleted dogs

In certain conditions, renal prostaglandins (PGs) are important determinants of kidney function. Under these "renal PG-dependent states," pharmacological inhibition of vasodilatory PG may result in excessive renal vasoconstriction and adversely affect kidney function. The purposes of this study were to determine whether acetaminophen (Acet), a weak PG-synthesis inhibitor, influences kidney function in the renal PG-dependent state of anesthesia and sodium depletion. Comparisons were made with ibuprofen (Ibu). Measurements of PGE2 excretion were used to assess renal PG synthesis. Acet (15 mg/kg) and Ibu (10 mg/kg) both decreased renal blood flow and glomerular filtration rate by approximately 20-30% in normal, anesthetized, sodium-replete dogs. Although Acet produced similar changes in renal blood flow and glomerular filtration rate in the low-sodium dogs, Ibu caused a significantly greater renal vasoconstriction (64 +/- 10%) in these animals. Both Acet and Ibu inhibited urinary PGE2 excretion in sodium-replete and low-sodium dogs. Ibu tended to have a greater and more prolonged effect than did Acet. These results suggest that Acet alters PGE2 excretion and kidney function under renal PG-dependent conditions; the effects, however, are less severe than those seen with Ibu.

Meloxicam: influence on arachidonic acid metabolism. Part II. In vivo findings

Meloxicam is a new nonsteroidal anti-inflammatory drug (NSAID) derived from enolic acid. Preclinical studies have indicated that meloxicam has potent anti-inflammatory activity, together with a good gastrointestinal and renal tolerability profile. This report summarizes studies undertaken to compare meloxicam to other NSAIDs in the inhibition of the inducible cyclooxygenase (COX-2) in inflamed areas (pleurisy of the rat, peritonitis of mice) and their influence on the activity of the constitutive cyclooxygenase (COX-1) in stomach, kidney, brain, and blood. In pleurisy of the rat, meloxicam was twice as potent as tenoxicam, 3 times as potent as flurbiprofen, 8 times as potent as diclofenac, and 20 times as potent as tenidap at inhibiting prostaglandin E2 (PGE2) biosynthesis. In the peritonitis model in mice, meloxicam was approximately twice as active as piroxicam, and more than 10 times as active as diclofenac in the suppression of PGE biosynthesis. Doses of meloxicam sufficient to inhibit PGE2 biosynthesis in the pleural exudate and peritoneal exudate had no influence on leukotriene-B4 (LTB4) or leukotriene-C4 (LTC4) content. The effect of meloxicam on the PGE2 content of rat gastric juice and rat urine was weaker than that of piroxicam or diclofenac. Meloxicam was a weaker inhibitor of the increased PGE2 concentration in brain of rats and mice (induced by convulsant doses of pentetrazole) than piroxicam, diclofenac, or indomethacin. Meloxicam had a weaker effect on serum thromboxane-B2 (TXB2) concentration in rats than piroxicam or tenoxicam. The in vivo findings confirm the results of in vitro tests, conducted separately, showing that meloxicam preferentially inhibits COX-2 over COX-1. COX-2 is the inducible isoenzyme implicated in the inflammatory response, whereas COX-1 has cytoprotective effects in the gastric mucosa. Therefore, a preferential selectivity for one isoenzyme over another, as displayed by meloxicam, may have implications in the clinical setting in terms of a more favorable risk: benefit profile.

Renal effects of over-the-counter analgesics

Recent case reports have shown that over-the-counter (OTC) analgesics, which are generally considered to be a safe treatment for minor aches and pains and fever, may cause adverse renal effects. Many renal syndromes induced by nonsteroidal antiinflammatory drugs (NSAIDs) can be attributed to prostaglandin inhibition. Fluid and electrolyte disturbances, acute renal failure, and acute interstitial nephritis also occur predominantly with NSAIDs. Acetaminophen lacks significant peripheral prostaglandin inhibition and may be a preferred first-line agent, particularly in patients susceptible to the induction of renal impairment. Apart from obvious clinical overdosage situations, limited reports of adverse renal effects exist with acetaminophen. Some studies have reported an association between analgesic nephropathy, one of the most severe analgesic-related adverse renal effects, and long-term abuse of phenacetin, acetaminophen, aspirin, ibuprofen, analgesic combinations, or other NSAIDs, although for some of these agents, this relationship is controversial. The overall risk for serious renal effects with OTC analgesics appears to be low, but given the accessibility and vast number of persons taking these agents, the absolute number of patients affected may be substantial. Therefore, it is important that healthcare providers recognize the risk factors for adverse analgesic-related renal effects.

The interaction of paracetamol with frusemide

Following the administration of paracetamol (1 g 4 times per day) or placebo to 10 healthy female volunteers for 2 days, the pharmacological effects of intravenous frusemide (20 mg) were observed after a final dose of either paracetamol or placebo. Paracetamol pre-treatment had no effect on frusemide-induced diuresis or natriuresis. There was a significant reduction in the basal output of prostaglandin E2 (PGE2) with paracetamol pre-treatment (18.4 +/- 15.4 vs 7.6 +/- 5.0 ng h-1, P < 0.05; 95% confidence interval of the difference 0.2 to 21.8). Frusemide induced a transient increase in the urinary excretion rate of PGE2 and although this effect was reduced by paracetamol (46.6 +/- 50.9 vs 23.2 +/- 13.8) the differences in the change of excretion rate from baseline were not statistically significant (95% confidence interval of the difference -17.8 to 15.7). The basal level of 6-keto prostaglandin F1 alpha (PGF1 alpha) was less with paracetamol pre-treatment (61.7 +/- 41.1 vs 38.7 +/- 26.1 ng h-1, NS; 95% confidence interval of the difference -16.6 to 62.6) and the cumulative urinary output of PGF1 alpha in the 6 h after frusemide administration was significantly reduced (305.9 +/- 179.4 vs 181.8 +/- 100.2 ng h-1, P < 0.05; 95% confidence interval of the difference 32.2 to 216). The frusemide-induced rise in plasma renin activity was significantly less with paracetamol than placebo at 60 min (4.3 +/- 2.9 vs 2.7 +/- 1.9 ng ml-1 h-1, P < 0.01; 95% confidence interval of the difference 0.4 to 2.7).