Rational aspirin dosage regimens

Preparation and Characterization of Honokiol Nanosuspensions and Preliminary Evaluation of Anti-Inflammatory Effect

The study mainly aimed to improve the solubility of honokiol (HK) by preparing honokiol nanosuspensions (HNS). In this study, HNS were obtained using Kolliphor®P407 (P407) as a stabilizer through melting method combined with high pressure homogenization (HPH). The crystalline state of HNS was confirmed through differential scanning calorimetry (DSC) and X-ray Diffraction (XRD). In vitro, the dissolution rate of HNS was significantly improved than that of pure HK. In vivo, higher anti-inflammatory activity was achieved after free HK had been made into HNS. There was no significant difference between the degree of edema (DE) of HNS group and that of aspirin group. Consequently, melting method combined with HPH was a potent technique to prepare HNS. Furthermore, nanosuspension was a valid formulation that could be utilized to enhance the anti-inflammatory effect of HK.

Differences in the metabolism and pharmacokinetics of two structurally similar PPAR agonists in dogs: involvement of taurine conjugation

1. The metabolism and pharmacokinetics of two structurally similar PPAR agonists, MRL-I, (2R)-7-[3-[2-chloro-4-(4-fluorophenoxy)phenoxy]propoxy]-2-ethyl-3,4-dihydro-2H-benzopyran-2-carboxylic acid, and MRL-II, (2R)-7-[3-[2-chloro-4-(2,2,2,-trifluoroethoxy)phenoxy]propoxy]-3,4-dihydro-2-methyl-2H-benzopyran-2-carboxylic acid, in dogs were investigated. 2. MRL-I was absorbed rapidly in dogs and exhibited linear pharmacokinetics over the dose range examined, 1-25mgkg(-1). In contrast, the pharmacokinetics of MRL-II were non-linear following both intravenous and oral administration. 3. The acyl glucuronide (AG) conjugate was the only radioactive component detected in bile from dogs dosed with [14C]MRL-I, whereas bile from dogs dosed with [14C]MRL-II contained varying amounts of both the AG and taurine conjugates. The percentages of the acyl glucuronide and taurine conjugates of [14C]MRL-II in dog bile were dose dependent. A higher percentage of radioactivity was associated with the taurine conjugate (about 41%) following intravenous administration at 0.2mgkg(-1) than at 0.9mgkg(-1) (about 14%) or oral administration at 5 mgkg(-1) (about 6%). The decrease in the percentage of radioactivity associated with the taurine conjugate at 0.9 mgkg(-1) was accompanied by a concomitant increase in the amount of the acyl glucuronide. 4. MRL-I, but not MRL-II, was subject to significant enterohepatic recirculation in dogs. Continuous collection of bile resulted in an 11-fold decrease in the terminal half-life of MRL-I in plasma (1.5 versus 16.6 h), and a 2.4-fold increase in its plasma clearance (4.0 versus 1.7 ml min(-1) kg(-1)) after intravenous administration at 1 mg kg(-1). 5. Collectively, the data suggest that the presence and subsequent saturation of the taurine conjugation pathway might have contributed to the non-linear pharmacokinetics of MRL-II in the dog.

Salicylate measurement: clinical usefulness and methodology

The salicylates are the most commonly used analgesic, antipyretic, and anti-inflammatory drugs. They are available in hundreds of preparations, many of which are over-the-counter medications. The easy access to large quantities of the drug and the widespread perception that the drug is harmless have contributed to salicylate intoxication becoming a serious and common problem, particularly among the pediatric and geriatric populations. Salicylate is still the major drug for the treatment of rheumatic diseases. The use of salicylate in high doses for the management of these patients requires close monitoring of serum salicylate levels because of the large interindividual variation in dose-serum level relationships and the narrowness of the therapeutic range. Thus, both for the management of patients intoxicated with salicylate and patients who are on high-dose salicylate therapy, the measurement of serum salicylate levels is an important clinical laboratory service. Recent research on the inhibitory effect of aspirin on platelet aggregation has led to the prophylactic use of aspirin in low doses as an antithrombotic drug. This new therapeutic use of aspirin can be aided by monitoring low serum levels of salicylate and perhaps aspirin itself. This article reviews the current state of the knowledge of the pharmacokinetics and clinical toxicology of salicylate, the clinical usefulness of salicylate measurement by the clinical laboratory, and recent development in the analytical technology for salicylate analysis.

Naproxen and acetylsalicylic acid in the treatment of pauciarticular and polyarticular juvenile rheumatoid arthritis. Assessment of tolerance and efficacy in a single-centre 24-week double-blind parallel study

Naproxen (NAP) (10 mg/kg/day) and acetylsalicylic acid (ASA) (75 mg/kg/day) were compared in a 24-week randomized block, controlled, parallel, double-blind study in 80 patients with pauciarticular or polyarticular juvenile rheumatoid arthritis. Five NAP-treated compared with 20 ASA-treated patients stopped therapy because of adverse reactions. Both drug regimens seemed to be therapeutically effective. The outcome of the study indicated that ASA may have a slight advantage over NAP with regard to efficacy. However, the changes in disease activity measurements were similar in the two treatment groups.

Factors determining efficacy of NSAIDs

This article reviews the efficacy of NSAIDs and their pharmacokinetic and pharmacodynamic properties. The assumption that classic pharmacokinetic dose/plasma concentration response relationships can be applied to NSAIDs has tenuous support in the biomedical literature. Comparative efficacy studies, using ASA and indomethacin as the standards for comparison, ignore the fact that the major outcome variables are subjective responses among patients, not among drugs. Comparing inhibition of platelet malonyldialdehyde, synovial drug concentrations, urinary prostaglandin metabolites, and plasma free and total concentration with the clinical outcome provides no guidelines to serve as predictors of response. The individual agents, indomethacin, salicylates, sulindac, piroxicam, and naproxen, illustrate the complexities of NSAID pharmacotherapy. Recent proliferation of newer NSAIDs will not add significantly to the efficacy of these agents in the treatment of pain and inflammatory disease states. However, knowledge of pharmacokinetic population parameters for the individual NSAIDs will increase the likelihood of therapeutic success and diminish the possibilities for adverse reactions.

Pharmacokinetics of aspirin and salicylate in elderly subjects and in patients with alcoholic liver disease

Plasma aspirin, salicylate and salicyluric acid concentrations were monitored in young, elderly and alcoholic subjects after ingestion of a single 1.2 g dose of soluble aspirin. The plasma aspirin, salicylate and unbound salicylate concentration-time profiles varied considerably between individual subjects. Most of the pharmacokinetic parameters derived from these profiles were not significantly different between young subjects, elderly subjects and subjects with alcoholic liver disease. Individual plasma albumin concentrations provided a better index of the unbound plasma salicylate clearances and salicylate plasma protein binding than the age of the subject or the presence of alcoholic liver disease. Highest unbound plasma salicylate concentrations were found in subjects with the lowest plasma albumin concentrations.

Clinical pharmacokinetics of salicylates: a re-assessment

1 Aspirin is partly hydrolyzed to salicylic acid during absorption. Absorbed aspirin is rapidly hydrolyzed systemically. Salicylic acid elimination kinetics are dependent on drug concentration due to the limited capacity of two major biotransformation pathways: formation of salicyluric acid and of salicylphenolic glucuronide. 2 The time courses of the various pharmacological effects of single doses of aspirin are not directly coincident with the plasma concentrations of either aspirin or salicylic acid but there is reasonably good evidence that the pharmacological effects are related to the concentration of aspirin, salicylic acid, or both. 3 Steady-state plasma salicylate concentrations increase more than proportionally with increasing daily dose; the time required to reach steady state increases with increasing daily dose. Dosage intervals of 8 or even 12 h are usually sufficient to maintain plasma salicylate concentrations in the anti-inflammatory concentration range. Monitoring of plasma salicylate concentrations in this range is facilitated by the relatively small drug concentration fluctuations during a dosing interval at steady-state. 4 Limited data suggest that the pharmacological activity of salicylate is produced by free (unbound) drug. As the plasma protein binding of salicylic acid is concentration-dependent and subject to pronounced interindividual differences, it is preferable, at least in principle, to monitor free rather than total concentrations of salicylate in plasma. Although salicylate concentration in saliva reflects the free rather than total salicylate concentration in plasma or serum, use of saliva for indirect monitoring of plasma salicylate concentrations seems to be impractical for technical reasons.

Aspirin dosage for infants and children

The labeled dosage schedule that has long been on pediatric aspirin preparations is at variance with the recommendation in authoritative medical references, studies demonstrating antipyretic effectiveness in children, and the prescribing habits of pediatricians as revealed by a poll conducted by the authors. Aspirin pharmacokinetics are influenced by a number of physiologic factors, as well as by dosage, and complicate the problem of assuring safe and effective pediatric use. Basic pharmacokinetic considerations indicate that the increase in size of individual doses needed to assure therapeutic salicyate blood levels, thereby removing the temptation of parents to administer the drug too often, is made permissible (i.e., safe while effective) by expanding the interdose interval to four hours instead of three. A revised pediatric aspirin disage schedule is presented that better meets the practices of the pediatric community and the needs of consumers.

Pharmacokinetic monitoring of salicylate therapy in children with juvenile rheumatoid arthritis

Free and total (sum of free and protein bound) salicylate concentrations in serum were determined in 17 children (age: 4-17 years) with definite juvenile rheumatoid arthritis. These measurements were carried out immediately before and 2, 4, and 8 hours after the morning dose during a strict 8 hourly aspirin treatment regimen (regular tablets) started 5 days earlier. The ratio of the 0 to 8 hour total salicylate concentrations was 0.95 +/- 0.10 (mean +/- SD), indicating that steady state had been attained. The ratio of the maximum to minimum concentrations during the dosing interval ranged from 1.05 to 2.26 and decreased with increasing average concentration. The concentration ratio was less than 1.3 at average salicylate concentrations above 20 mg/100 ml. It is concluded that the timing of a blood sample is not critical for monitoring steady state serum salicylate concentrations in the usual therapeutic range if the dosing interval is 8 hours or less. Free salicylate concentrations increased more than proportionately with increasing total concentrations due to the concentration dependent protein binding of the drug in serum.

Dosage of salicylates for children with juvenile rheumatoid arthritis. A prospective clinical trial with three different preparations of acetylsalicylic acid

41 children with juvenile rheumatoid arthritis (JRA) and 6 with postinfectious arthropathies, aged 3--15 years, were treated with acetylsalicylic acid for 14 days during which time the patients were hospitalized. Three different acetylsalicylic acid preparations were used: a microencapsulated form, an enteric-coated form and standard acetylsalicylic acid tablets. Serum salicylate concentrations were measured by Trinder's photometric method. With doses of 90--120 mg/kg/day symptoms of salicylism appeared in about 50% of the cases. Daily doses of 2 g/m2 (not exceeding 70 mg/kg) proved relatively safe in this study, whereas symptoms and signs of intoxication appeared at doses exceeding 3 g/m2/day. In this respect there were no significant differences between the three acetylsalicylic acid preparations used. The results of this study also suggest that the serum salicylate concentrations should not exceed 2000 mumol/l (about 27 mg/100 ml). The symptoms of salicylism correlated closely with serum salicylate levels, which, in turn, correlated well with the dosage in g/m2. Elevation of serum aspartate aminotransferase was noted in 1/3 of the cases. All of these had a dose exceeding 2 g/m2, and the frequency of elevated enzyme activities increased with increasing dosage. In the group receiving enteric coated form of acetylsalicylic acid, there were fewer positive benzidine tests (12%) than in the two other groups (22--28%).

Steady-state serum salicylate levels in hospitalized patients with rheumatoid arthritis. Comparison of two dosage schedules of choline magnesium trisalicylate

When the total daily drug dose was individualized to produce a steady-state serum salicylate concentration between 20 and 35 mg/dl, clinically acceptable fluctuations of serum concentrations occurred during both twice daily and three times daily administration. In 6 rheumatoid arthritis patients receiving choline magnesium trisalicylate, mean steady-state serum levels were the same, and the ranges of hourly mean concentrations during 8 and 12 hour dosage intervals were 19 to 27 mg/dl and 17 to 30 mg/dl, respectively. Changing the dosing interval from 8 to 12 hours required a 50% increase in the fractional doses, but resulted in an increase of only 3 mg/dl in mean peak concentration and a ddecrease of 1 mg/dl in mean minimum concentration.