Steady state pharmacokinetics of piroxicam in children with rheumatic diseases

Physiologically based pharmacokinetic (PBPK) modeling of piroxicam with regard to CYP2C9 genetic polymorphism

Piroxicam is a non-steroidal anti-inflammatory drug used to alleviate symptoms of osteoarthritis and rheumatoid arthritis. CYP2C9 genetic polymorphism significantly influences the pharmacokinetics of piroxicam. The objective of this study was to develop and validate the piroxicam physiologically based pharmacokinetic (PBPK) model related to CYP2C9 genetic polymorphism. PK-Sim^® version 10.0 was used for the PBPK modeling. The PBPK model was evaluated by predicted and observed plasma concentration-time profiles, fold errors of predicted to observed pharmacokinetic parameters, and a goodness-of-fit plot. The turnover number (k_cat) of CYP2C9 was adjusted to capture the pharmacokinetics of piroxicam in different CYP2C9 genotypes. The population PBPK model overall accurately described and predicted the plasma concentration-time profiles in different CYP2C9 genotypes. In our simulations, predicted AUC_inf in CYP2C9*1/*2, CYP2C9*1/*3, and CYP2C9*3/*3 genotypes were 1.83-, 2.07-, and 6.43-fold higher than CYP2C9*1/*1 genotype, respectively. All fold error values for AUC, C_max, and t_1/2 were included in the acceptance criterion with the ranges of 0.57-1.59, 0.63-1.39, and 0.65-1.51, respectively. The range of fold error values for predicted versus observed plasma concentrations was 0.11-3.13. 93.9% of fold error values were within the two-fold range. Average fold error, absolute average fold error, and root mean square error were 0.93, 1.27, and 0.72, respectively. Our model accurately captured the pharmacokinetic alterations of piroxicam according to CYP2C9 genetic polymorphism.

Pharmacokinetics of meloxicam in patients with juvenile rheumatoid arthritis

The pharmacokinetics of a meloxicam suspension were studied in 18 children with juvenile rheumatoid arthritis. Children received a single 0.25-mg/kg dose up to a maximum of 15 mg. Pharmacokinetic parameters after the first dose were calculated by noncompartmental methods. Geometric mean (percent coefficient of variation for geometric mean [gCV]) C(max), AUC(0- infinity ), apparent clearance, apparent volume of distribution, and elimination half-life values were 1.24 microg/mL (47% gCV), 25.6 microg x h/mL (81% gCV), 0.17 mL/min/kg (83% gCV), 0.19 L/kg (63% gCV), and 13.4 hours (54% gCV) in the younger group and 1.89 microg/mL (25% gCV), 35.8 microg x h/mL (21% gCV), 0.12 mL/min/kg (23% gCV), 0.13 L/kg (22% gCV), and 12.7 hours (21% gCV) for the older group, respectively. Area under the curve, volume of distribution, and clearance tended to be higher in the younger group, whereas elimination half-lives were similar. A post hoc comparison to pharmacokinetic data in adults revealed no relevant differences. Thus, a common body weight-normalized dose is considered appropriate for children older than 2 years.

A pharmacokinetic study of piroxicam in children

Feldene Melt (piroxicam) is commonly used for analgesia following day case surgery. The manufacturer's recommended paediatric dose is 0.4 mg.kg(-1) once daily. In children, plasma piroxicam levels of 3-5 microg.ml(-1) are associated with effective analgesia. However, in adults a single dose of 20 mg piroxicam (0.4 mg.kg(-1) for a 50-kg adult) produces plasma levels of only 1.5-2.2 microg.ml(-1). We therefore studied plasma levels achieved by 0.4 mg.kg(-1) or 1.0 mg.kg(-1) piroxicam in 22 children aged between 3 and 16 years, undergoing elective orthopaedic surgery, in order to investigate the adequacy of single dosing. The first 12 patients received 0.4 mg.kg(-1) Feldene Melt pre-operatively. Following assay of plasma piroxicam levels, a further 10 patients received 1.0 mg.kg(-1) Feldene Melt. In both groups, five blood samples were taken at 2-hourly intervals. The mean (95% CI) piroxicam level following 0.4 mg.kg(-1) was 2.90 (2.33-3.54) microg.ml(-1), compared to 5.87 (4.58-7.16) microg.ml(-1) following 1.0 mg.kg(-1) (p = 0.0003).

Risks and benefits of nonsteroidal anti-inflammatory drugs in children: a comparison with paracetamol

Nonsteroidal anti-inflammatory drugs (NSAIDs) possess antipyretic, analgesic and anti-inflammatory effects. They are frequently used in children and have numerous therapeutic indications, the most common ones being fever, postoperative pain and inflammatory disorders, such as juvenile idiopathic arthritis (JIA) and Kawasaki disease. Their major mechanism of action is through inhibition of prostaglandin biosynthesis by blockade of cyclo-oxygenase (COX). The disposition of most NSAIDs has been mainly studied in infants > or = 2 years of age. Compared with adults, the volume of distribution and clearance of NSAIDs such as diclofenac, ibuprofen (infants aged between 3 months and 2.5 years), ketorolac and nimesulide were increased in children. The elimination half-life was similar in children to that in adults. These pharmacokinetic differences might be clinically significant with the need for higher loading and/or maintenance doses in children. Ibuprofen, acetylsalicylic acid (ASA) and acetaminophen are the most frequently used agents for fever reduction in children. Over the past 20 years, because of the association between ASA use and Reye's syndrome, most of the interest has been directed toward ibuprofen and acetaminophen. In view of its comparable antipyretic efficacy, but superior tolerability profile, acetaminophen, when used appropriately with age-adapted formulations, should remain the first-line therapy in the treatment of childhood fever. At the moment, there is no scientific evidence to recommend simultaneous use of these two antipyretic drugs. Most NSAIDs provide mild to moderate analgesia, with the exception of ketorolac which has a strong analgesic activity. The analgesic efficacy of ketorolac, ketoprofen, diclofenac and ibuprofen in the treatment of postoperative pain has been mainly studied following a single dose, in children of > or = 1 year of age undergoing minor surgeries. In this setting, when used either alone or in adjunct to caudal or epidural anaesthesia, they were associated with an opioid-sparing effect and were well tolerated. With the exception of ketorolac use in children undergoing tonsillectomy, where controversy exists regarding the risk of postoperative haemorrhage, NSAIDs have not been associated with an increased risk of perioperative bleeding. NSAIDs are the first-line therapy in JIA. They appear to be equally effective and tolerated, with the exception of ASA which is associated with more adverse effects. ASA has been used for many years in the treatment of Kawasaki disease and is part of the standard modality of treatment in combination with intravenous gammaglobulins. More recently, lung inflammation associated with cystic fibrosis (CF) has become a new target for NSAIDs. Despite promising preliminary results with ibuprofen, numerous questions need to be answered before this new strategy becomes part of the conventional treatment of patients with CF. In summary, NSAIDs are effective in reducing fever, alleviating pain and reducing inflammation in children, with a good tolerance profile. Pharmacokinetic studies are needed to characterise the disposition of NSAIDs in very young infants in order to use them rationally. To date, no studies have been published on the disposition, tolerability and efficacy of specific COX-2 inhibitors in children. Further clinical experience with these agents in adults is warranted before undergoing trials with specific COX-2 inhibitors in children.

Pharmacokinetics of etodolac in patients with stable juvenile rheumatoid arthritis

This was a single-center, open-label, single-dose pharmacokinetic study of etodolac in pediatric and adolescent patients with stable juvenile rheumatoid arthritis (JRA). Eleven male and female patients with JRA (8.1 to 14.8 years of age, weighing 26.4 to 59.5 kg) received a single oral dose of etodolac (200, 300, or 400 mg based on body weight). Clinical laboratory measurements, measurement of vital signs, and physical examinations were performed to monitor safety. Concentrations of etodolac were determined in plasma using high-performance liquid chromatography with ultraviolet detection with a limit of quantitation of 0.2 mg/L and were analyzed using a noncompartmental pharmacokinetic method. Pharmacokinetic parameters observed were consistent in magnitude and degree of variability with data from healthy adult subjects receiving a single 400- or 600-mg dose of etodolac. Although the mean fraction of unbound drug in patients with JRA was higher than in healthy adults, the oral clearance was independent of age. No serious adverse events occurred during this study. Etodolac yielded consistent pharmacokinetic values among stratified dose subgroups. Single doses of all etodolac treatments were well tolerated in both pediatric and adolescent patients.

Toxicity of antirheumatic and anti-inflammatory drugs in children

The aim of the study was to describe the long-term toxicity of antirheumatic and anti-inflammatory drugs in a paediatric rheumatology clinic population. One hundred and seventeen children were studied on first admission to a paediatric rheumatology clinic and after a mean of 8.6 +/- 0.4 years of follow-up. Medical records from the intermediate period were reviewed. The patients had 155 exposures to non-steroidal anti-inflammatory drugs (NSAIDs), 88 exposures to disease-modifying antirheumatic drugs (DMARDs) and 12 exposures of prednisolone during a total of 682 patient years. Drug toxicity was measured in terms of the number of toxic events, number of drug discontinuations due to toxicity, number of side-effects per patient year of drug exposure and as a toxicity index. Side-effects were seen in 69 (27%) of the drug exposures, corresponding to 0.10 toxic events per patient year of exposure. Abdominal pain was the most common side-effect, and was reported in 21 (14%) of the exposures to NSAIDs. Five severely toxic events, all leading to hospitalisation, occurred. The toxicity of NSAIDs was not significantly different from that of DMARDs with regard to the number of toxic events (21% and 31%, respectively, NS) and drug discontinuations due to toxicity (17% and 14%, respectively, NS). Piroxicam tended to be more toxic than ibuprofen (46% versus 18% toxic events, p <0.05; 36% versus 16% discontinuations due to toxicity, NS; 0.33 versus 0.05 side-effects per patient year and a toxicity index of 1.45 versus 0.20 units per patient year). Gold tended to be more toxic than antimalarials (41% versus 15% toxic events, p<0.05; 24% versus 12% discontinuations, NS; 0.37 versus 0.08 side-effects per patient year and a toxicity index of 1.56 versus 0.23 units per patient year). It was concluded that antirheumatic and anti-inflammatory drugs led to side-effects in 27% of the exposed children during 9 years of follow-up. There was an overlap of the toxicity of certain NSAIDs and the most commonly employed DMARDs.

Pharmacokinetics of oxicam nonsteroidal anti-inflammatory agents

Oxicam nonsteroidal anti-inflammatory drugs (NSAIDs) are a group of structurally closely related substances with anti-inflammatory, analgesic and antipyretic activities. They have a weakly acidic character and are extensively bound to plasma proteins. Piroxicam, the most widely used oxicam, is well absorbed after oral administration. Peak plasma concentrations (Cmax) of the drug are reached within 2 to 4 hours. Piroxicam has a small volume of distribution and a low plasma clearance. It undergoes hepatic metabolism and only 5 to 10% is excreted unchanged in urine. The elimination half-life varies between 30 and 70 hours. Age of the patient and renal or hepatic dysfunction do not seem to have any major effect on the pharmacokinetics of piroxicam. The drug reduces the renal excretion of lithium to a clinically significant extent, but the clinical significance of piroxicam-aspirin (acetylsalicylic-acid) and piroxicam-acenocoumarol interaction has not been established. Ampiroxicam, droxicam and pivoxicam are prodrugs of piroxicam that have been synthesised to reduce piroxicam-related gastrointestinal irritation. All prodrugs are well absorbed, but Cmax values are reached later than those following administration of piroxicam. Tenoxicam is used in the management of rheumatic and inflammatory diseases. Mean Cmax values are achieved 2 hours postdose. Food reduces the rate but not the extent of absorption. The oral bioavailability of tenoxicam is 100% and rectal bioavailability is 80%. Like piroxicam, tenoxicam has a low volume of distribution and low plasma clearance. It is eliminated through hepatic metabolism. The mean elimination half-life is 60 to 75 hours. The pharmacokinetics of tenoxicam are independent of patient age, or concurrent liver or renal diseases. High doses of aspirin have been shown to increase the elimination of tenoxicam, but this has little clinical significance. Isoxicam was in widespread clinical use until its worldwide marketing was suspended because of fatal skin reactions. Isoxicam is completely absorbed, but Cmax values are not reached until 10 hours postdose. It has a low plasma clearance, approximately 5 ml/min (0.3 L/h), and low volume of distribution. The mean elimination half-life is 30 hours and does not appear to be affected by the age of the patient. Isoxicam potentiated the anticoagulant effect of warfarin, necessitating a 20% dosage reduction. Lornoxicam differs from other oxicam NSAIDs because it has a short elimination half-life of 3 to 4 hours. On the basis of limited data, some individuals seem to eliminate lornoxicam very slowly, suggesting the presence of polymorphic metabolism. The pharmacokinetics of cinnoxicam and sudoxicam have not been studied thoroughly.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-steroidal anti-inflammatory drugs and slow-acting anti-rheumatic drugs in juvenile rheumatoid arthritis

The preferred drugs for the initial treatment of juvenile rheumatoid arthritis (JRA) are salicylates or other non-steroidal anti-inflammatory drugs (NSAID) such as tolmetin or naproxen. If the disease activity does not respond adequately to the treatment, slow-acting anti-rheumatic drugs (SAARD) such as oral gold agents, low-dose D-penicillamine, or sulfasalazine should be given in addition to NSAID. If the systemic manifestations are severe, corticosteroid therapy may be commenced. Furthermore, if the joint destruction is progressive, immunosuppressants such as methotrexate would be selected as the third-line drugs of choice. The safety and efficacy of SAARD and immunosuppressants for the treatment of children with JRA, however, have not yet been confirmed, as the adverse effects such as bone marrow suppression, oncogenicity and mutagenicity are sometimes intense. Consequently, the strict indications for use and new therapeutic concepts for the management of JRA based on its pathogenesis are required.