Pharmacokinetics of 5-aminosalicylic acid from controlled-release capsules in man

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Treatment of Ulcerative Colitis

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) of unknown etiology, probably caused by a combination of genetic and environmental factors. The treatment of patients with active UC depends on the severity, localization and history of IBD medication. According to the classic step-up approach, treatment with 5-aminosalicylic acid compounds is the first step in the treatment of mild to moderately active UC. Corticosteroids, such as prednisolone are used in UC patients with moderate to severe disease activity, but only for remission induction therapy because of side effects associated with long-term use. Thiopurines are the next step in the treatment of active UC but monotherapy during induction therapy in UC patients is not preferred because of their slow onset. Therapeutic drug monitoring (TDM) of the pharmacologically active metabolites of thiopurines, 6-thioguanine nucleotide (6-TGN), has proven to be beneficial. Thiopurine S-methyltransferase (TMPT) plays a role in the metabolic conversion pathway of thiopurines and exhibits genetic polymorphism; however, the clinical benefit and relevance of TPMT genotyping is not well established. In patients with severely active UC refractory to corticosteroids, calcineurin inhibitors such as ciclosporin A (CsA) and tacrolimus are potential therapeutic options. These agents usually have a rather rapid onset of action. Monoclonal antibodies (anti-tumor necrosis factor [TNF] agents, vedolizumab) are the last pharmacotherapeutic option for UC patients before surgery becomes inevitable. Body weight, albumin status and antidrug antibodies contribute to the variability in the pharmacokinetics of anti-TNF agents. Additionally, the use of concomitant immunomodulators (thiopurines/methotrexate) lowers the rate of immunogenicity, and therefore the concomitant use of anti-TNF therapy with an immunomodulator may confer some advantage compared with monotherapy in certain patients. TDM of anti-TNF agents could be beneficial in patients with primary nonresponse and secondary loss of response. The potential benefit of applying TDM during vedolizumab treatment has yet to be determined.

Measurement of in vivo Gastrointestinal Release and Dissolution of Three Locally Acting Mesalamine Formulations in Regions of the Human Gastrointestinal Tract

As an orally administered, locally acting gastrointestinal drug, mesalamine products are designed to achieve high local drug concentration in the gastrointestinal (GI) tract for the treatment of ulcerative colitis. The aim of this study was to directly measure and compare drug dissolution of three mesalamine formulations in human GI tract and to correlate their GI concentration with drug concentration in plasma. Healthy human subjects were orally administered Pentasa, Apriso, or Lialda. GI fluids were aspirated from stomach, duodenum, proximal jejunum, mid jejunum, and distal jejunum regions. Mesalamine (5-ASA) and its primary metabolite acetyl-5-mesalamine (Ac-5-ASA) were measured using LC-MS/MS. GI tract pH was measured from each GI fluid sample, which averaged 1.82, 4.97, 5.67, 6.17, and 6.62 in the stomach, duodenum, proximal jejunum, middle jejunum, and distal jejunum, respectively. For Pentasa, high levels of 5-ASA in solution were observed in the stomach, duodenum, proximal jejunum, mid jejunum, and distal jejunum from 1 to 7 h. Apriso had minimal 5-ASA levels in stomach, low to medium levels of 5-ASA in duodenum and proximal jejunum from 4 to 7 h, and high levels of 5-ASA in distal jejunum from 3 to 7 h. In contrast, Lialda had minimal 5-ASA levels from stomach and early small intestine. A composite appearance rate (CAR) was calculated from the deconvolution of individual plasma concentration to reflect drug release, dissolution, transit, and absorption in the GI tract. Individuals dosed with Pentasa had high levels of CAR from 1 to 10 h; individuals dosed with Apriso had low levels of CAR from 1 to 4 h and high levels of CAR from 5 to 10 h; Lialda showed minimal levels of CAR from 0 to 5 h, then increased to medium levels from 5 to 12 h, and then decreased to further lower levels after 12 h. In the colon region, Pentasa and Apriso showed similar levels of accumulated 5-ASA excreted in the feces, while Lialda showed slightly higher 5-ASA accumulation in feces. However, all three formulations showed similar levels of metabolite Ac-5-ASA in the feces. These results provide direct measurement of drug dissolution in the GI tract, which can serve as a basis for investigation of bioequivalence for locally acting drug products.

Is once-daily mesalazine equivalent to the currently used twice-daily regimen? A study performed in 30 healthy volunteers

A randomized, 2-way, crossover study was conducted in 30 volunteers to compare the pharmacokinetic profile of a new once-daily dosing regimen of mesalazine (1 x 4 g/d) with the current twice-daily dosage (2 x 2 g/d) used in many European countries. The 2 dosages were administrated orally for 8 days, separated by a 2-week washout. Plasma concentrations of mesalazine and N-acetyl-mesalazine were determined on days 1 and 8 by a validated high-performance liquid chromatography method and C(max), t(max), and AUCs calculated. The bioequivalence was obtained for a 90% confidence interval of the AUC(0-24h) ratio (test/reference) for mesalazine and N-acetyl-mesalazine on days 1 and 8, within the range of 0.80 to 1.25. The bioequivalence was demonstrated on day 1 for mesalazine and N-acetyl-mesalazine and on day 8 for mesalazine. As it is desirable to offer patients a preparation with a less frequent administration to enhance compliance, this once-daily regimen may be an attractive dosing option.

Clinical pharmacokinetics of slow release mesalazine

Slow release oral mesalazine (Pentasa) contains microgranules covered by a semipermeable ethylcellulose membrane. The microgranules continuously release their content from duodenum to ileum in a pH- and time-dependent way. About 75% of the microgranules pass into the colon, where further release is slower. This release pattern does not appear to be affected by food, diarrhoea or the simultaneous use of H2 antagonists. Rectal forms of mesalazine deliver active drug directly to the rectum and left colon. Plasma concentrations of mesalazine and its metabolite acetyl-5-aminosalicylic acid after oral or local administration are the result of systemic absorption and hepatic metabolism by N-acetyltransferase. Most studies report maximal plasma concentrations of less than 1 mg/L after oral administration of slow release mesalazine, much lower than those observed after uncoated mesalazine but generally higher than after azo-bound drugs such as sulfasalazine. Urinary recovery is an indicator of absorption and metabolism, and is lower after rectal administration (10 to 30%) than after oral administration (30 to 40%). Faecal recovery after oral administration of slow or delayed release mesalazine is lower than with azo-bound drugs. Mesalazine acts locally after absorption by colonic and ileal mucosa. Mean steady-state concentrations of 25.7+/-2.2 microg/kg wet weight are found in ileocolonic biopsy specimens from patients with irritable bowel syndrome treated for 1 week with slow release mesalazine 1.5 g/day. Intramucosal concentrations after slow release mesalazine differ little between healthy individuals and patients with inflammatory bowel disease. Although significant differences are found between the various aminosalicylates in release patterns and the resulting pharmacokinetic parameters, no differences in therapeutic effects have been found in comparative studies. High doses of oral mesalazine (2 to 4 g/day) are more effective than lower doses in the treatment of patients with mild to moderate active ulcerative colitis. High doses (4 g/day) are also effective in the treatment of Crohn's disease, predominantly in patients with ileitis. In contrast, no dose ranging effects were demonstrated with local treatment forms: mesalazine 1g enema seems sufficient for patients with distal colitis. Higher serum concentrations and urinary recoveries after the administration of slow or delayed release mesalazine compared with azo-bound drugs suggest a higher risk for renal adverse effects, although the reported occurrence is extremely low. Although preliminary data support an association between mucosal concentrations of mesalazine and its clinical activity, further studies are needed to correlate the effects of this drug with its pharmacokinetic parameters.

Prolonged-release mesalazine: a review of its therapeutic potential in ulcerative colitis and Crohn's disease

Prolonged-release mesalazine (Pentasa) consists of ethylcellulose-coated microgranules from which mesalazine (known in the US as mesalamine) is released in the small and large intestine in a diffusion-dependent manner. Dose-dependent improvements in clinical and endoscopic parameters have been reported with prolonged-release mesalazine 2 and 4 g/day in clinical trials in patients with mild to moderately active ulcerative colitis. Induction of clinical and endoscopic remission was achieved in more patients receiving a daily dosage of 4 g/day than in those receiving placebo. In patients with ulcerative colitis in remission, prolonged-release mesalazine is effective in reducing the rate of relapse. Higher dosages tend to be more effective, and a 12-month remission rate of 64% has been reported for patients treated with a 4 g daily dosage of this formulation. Comparative data indicate that prolonged-release mesalazine has similar efficacy in maintaining remission to molar equivalent doses of sulfasalazine. Data from a study in patients with mild to moderately active Crohn's disease indicates that higher dosages (4 g/day) of prolonged-release mesalazine are more effective than placebo in reducing disease activity. After 16 weeks' treatment, 64% of patients receiving a 4 g/day dosage experienced clinical improvement and 43% attained remission. In studies of patients in remission of Crohn's disease, the formulation appears to be more effective in preventing relapse in patients with isolated small bowel disease than in those with colonic involvement. The tolerability profile of oral prolonged-release mesalazine is similar to that of placebo and the incidence of adverse events does not appear to be dose-related. Nausea/vomiting, diarrhoea, abdominal pain and dyspepsia occur most frequently, although their incidence is low. Reports of nephrotoxicity during prolonged-release mesalazine treatment are rare.

CONCLUSIONS

Oral prolonged-release mesalazine is effective for maintenance and induction of remission of mild to moderately active colitis, both in patients with distal disease and in those with pancolitis. The formulation has similar efficacy to that of equimolar concentrations of sulfasalazine. Prolonged-release mesalazine also appears to be effective in the treatment of Crohn's disease, and maintenance therapy is of particular value in patients with isolated small bowel involvement. Evidence suggests that higher dosages (3 to 4 g/day) of prolonged-release mesalazine have additional therapeutic benefits over lower dosages in patients with inflammatory bowel disease without increasing the incidence of adverse events.

New preparation method of intestinal pressure-controlled colon delivery capsules by coating machine and evaluation in beagle dogs

A new method for preparing large amounts of pressure-controlled colon delivery capsules (PCDCs) which employs a pharmaceutical coating machine, Hicoater-mini, has been developed. In contrast to our original method for preparing PCDCs where the inner surfaces of gelatin capsule were coated with the water-insoluble polymer ethylcellulose (EC), PCDC were directly prepared by coating the capsular shaped suppositories with EC. As a model drug, fluorescein (FL) was used in this study. FL powder was suspended with the suppository base, polyethylene glycol (PEG) 1000, at 50 degreesC, and was hardened in the capsular shape the sizes of which were #0 and #2. The capsular shaped suppositories were coated with 5% w/v ethanolic EC (7G grade) solution by a coating machine. By increasing the coating time from 55 to 75 min, the mean coating thickness of #0 PCDCs increased from 141+/-7 to 211+/-4 micrometer. In the case of #2 PDDCs, the mean coating thickness increased from 102+/-3 to 110+/-5 micrometer by increasing the coating time from 35 min to 40 min. Several kinds of #0 PCDCs having the mean EC coating membrane thickness of 141+/-7 micrometer (type 1), 166+/-4 micrometer (type 2), 188+/-4 micrometer (type 3), 211+/-4 micrometer (type 4) as well as #2 PCDCs having thickness of 102+/-3 micrometer (type 5) and 110+/-5 micrometer (type 6) were used for in vivo evaluation using beagle dogs. After oral administration of the test preparations containing 30 mg of FL, blood samples were obtained from the jugular vein and plasma FL levels were measured. The first appearance time, Ti, of FL in the plasma was used as a parameter for the estimation of the release time of FL from PCDCs in the gastrointestinal tract. The mean Ti of #0 PCDCs were 2.3+/-0.5 for type 1, 3.3+/-0.5 for type 2, 4.8+/-1.0 for type 3 and 7.8+/-1.7 h for type 4 preparations while the mean Ti of #2 PCDCs were 3.2+/-0.4 for type 5 and 3.8+/-0.4 h for type 6, respectively. There were good correlations between EC coatings.

Evaluation of intestinal pressure-controlled colon delivery capsule containing caffeine as a model drug in human volunteers

The delivery ability of a pressure-controlled colon delivery capsule (PCDC) containing caffeine as a test drug was evaluated after oral administration to healthy male human volunteers. The driving force causing PCDC disintegration in the intestinal tract is the physiological luminal pressure which results from peristalsis. Three kinds of PCDCs having different thickness of a water-insoluble polymer membrane was prepared by coating the inner surface of the gelatin capsules with ethylcellulose (EC). The mean thickness were 40 +/- 1 (SE) for type 1, 44 +/- 1 for type 2 and 50 +/- 1 micron for type 3 PCDC, respectively. Caffeine was dissolved with a suppository base (PEGs 400 and 1000) and the capsules were filled. Doses were 15, 45 or 75 mg. After blank saliva samples were obtained, test preparations were orally administered to the volunteers and saliva samples were collected for 1 min intervals hourly from 1 to 10 h in the fasted state study, and from 1 to 20 h and at 25 h in the fed state study. Caffeine concentrations in the saliva samples were analyzed by HPLC. The maximum salivary caffeine excretion rate increased as the oral caffeine dose increased. The maximum salivary caffeine excretion rate increased predominantly compared to the pre-dose level in 75 mg dose study. Therefore, all following studies were performed with this dose. The first appearance time of caffeine into the saliva, TI, was used as a parameter to estimate the disintegration time of test preparations in the gastrointestinal tract. The mean TI of types 1, 2, and 3 PCDCs were 3.0 +/- 0.4, 4.0 +/- 0.4 and 4.5 +/- 0.3 h, respectively. After oral administration of 75 mg caffeine in pain gelatin capsule as a reference preparation, caffeine appeared in the saliva within 0.5 h. The mean hardness of the PCDCs were 1.05 +/- 0.10 (type 1), 1.55 +/- 0.06 (type 2) and 2.08 +/- 0.15 newton (type 3), respectively. There were good correlations between three parameters: EC coating membrane thickness, hardness and TI (determination coefficient r2 = 0.935 between TI and thickness, r2 = 0.998 between thickness and hardness, r2 = 0.958 between hardness and TI). The effect of food intake on the delivery ability was examined with type 3 PCDCs. Food intake prolonged the mean TI, from 4.5 +/- 0.3 to 7.8 +/- 1.3 h. This increase is thought to be ascribed to prolonged gastric emptying time. Comparison with reported colon arrival times indicates that the type 3 PCDC functions in colon delivery of caffeine and is thought to be applicable to other drugs.