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PubMed1983

Plasma prednisolone studies in rheumatic patients.

Prednisolone concentration in plasma after a daily maintenance steroid dose was monitored in 83 patients with rheumatic diseases. Although no restrictions were imposed on the intake of food or drink, plasma drug levels tended to peak at 1 h after the ingestion of the standard tablets, whereas intestinal absorption of the enteric-coated preparation was found to be most unpredictable. A profound individual variation was observed in plasma prednisolone concentrations, and neither total nor unbound drug levels showed any consistent relationship with the size of the prednisolone dose or the control of the disease activity. The basal cortisol production was suppressed in one-third of the patients. There is no support from this study for the concept of an 'optimum therapeutic range' of plasma prednisolone for the treatment of rheumatic disease.

Adult↗

PubMed1980

The prevalence of duodenal lesions in patients with rheumatic diseases on chronic aspirin therapy.

Peroral endoscopy was performed in 56 patients with rheumatic disease who had been taking 8 or more aspirin tablets daily for more than 3 months yet who had no major gastrointestinal symptoms or history of peptic ulcer disease. Duodenal mucosal lesions were observed in 16 patients; 15 (27%) had erythema, 7 (13%) had erosions, and 2 (4%) had ulcers. The prevalence of duodenal lesions was the same in patients taking regular, buffered, or enteric-coated aspirin preparations. Patients with duodenal lesions were more likely to have associated gastric lesions.

Adult↗

PubMed1979

Incidence of gastric lesions in patients with rheumatic disease on chronic aspirin therapy.

Endoscopy was done in 82 patients with rheumatic disease who were receiving chronic aspirin therapy. Fifty-eight patients were taking at least eight aspirin tablets daily for 3 or more months; 24 patients were taking, in addition to the aspirin, a maximum of one other antiinflammatory, nonsteroidal medication. Endoscopy in 45 normal subjects not taking aspirin showed no ulcers or erosions and a 4% incidence of gastric erythema. In the 82 patients with rheumatic disease, 14 (17%) had gastric ulcers, 33 (40%) had gastric erosions, and 62 (76%) had gastric erythema. Regular aspirin and buffered aspirin users had an ulcer incidence of 23% and 31% respectively, compared with a 6% incidence in enteric-coated aspirin users (P less than 0.05). One third of all patients with gastric ulcer had no gastrointestinal symptoms. Patients taking chronic aspirin therapy for rheumatic diseases have a higher than suspected incidence of gastric ulcer and erosions. Gastric ulcer may exist without symptoms in such patients.

Adult↗

PubMed1995

The effect of aspirin on haemostatic activity in the treatment of chronic venous leg ulceration.

An increased rate of venous ulcer healing with the use of oral enteric-coated aspirin (300 mg) daily has been reported. Whether the effect of aspirin in this condition is related to its action on the haemostatic mechanism is unclear, and therefore this study aimed to assess the effect of aspirin on some haemostatic parameters in patients with chronic venous leg ulcers. A double-blind, randomized, placebo-controlled, parallel-group study of haemostatic activity and the effect of aspirin was implemented over a 4-month period. Twenty patients with venous leg ulcers, and 20 age- and sex-matched controls were studied. Patients received enteric-coated aspirin (300 mg) or placebo (one tablet) daily for 4 months, in addition to standardized local compressive bandaging (Setopress). Assessments made at recruitment, and at 2 and 4 months, included measurement of total ulcer surface area, haematological and biochemical screening, measurement of coagulation times, coagulation factor VIII:C (FVIII:C) and von Willebrand factor (vWF), and plasminogen activator inhibitor-1 (PAI-1) levels. Procoagulant activity was assessed by a computer-assisted technique, to determine the rate of thrombin production in vitro. Patients with venous ulcers had increased levels of fibrinogen (P < 0.01), FVIII:C (P < 0.05), vWF (P < 0.05) and PAI-1 antigen (P < 0.01) compared with controls. Shortening of the coagulation rate, shown by a reduction of the time to generate 50% maximal thrombin activity in seconds (T50), was seen in patients, in comparison with control subjects (P < 0.05). T50 was longer in patients receiving aspirin than those receiving placebo, reflecting prolongation of coagulation rate in the aspirin-treated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspirin↗

PubMed1991

Pharmacokinetics of 2',3'-dideoxyinosine in patients with severe human immunodeficiency infection. II. The effects of different oral formulations and the presence of other medications.

2',3'-Dideoxyinosine (ddI) has shown activity against human immunodeficiency virus in phase I clinical trials. The drug is rapidly degraded by acid, however, thus raising questions as to the efficiency and reproducibility of its absorption after oral administration. This investigation studies the bioavailability of several oral dosage forms of ddI. When ddI was given to fasting patients as an oral solution with antacid, the bioavailability was 41% +/- 7% (mean +/- SEM). However, when given as buffered tablets, the bioavailability was considerably less (25% +/- 5%). The bioavailability increased slightly when the tablets were given with supplemental antacid (36% +/- 6%). Two enteric-coated preparations had reasonable bioavailability (36% +/- 5% and 26% +/- 5%), but the peak plasma level was much lower and occurred at a much later time than with the oral solution. When ddI was given as a premeasured powder containing sucrose and buffer to be reconstituted by the patient (the "sachet" preparation), the bioavailability was 29% +/- 6%. This was similar to that of the oral solution for this particular group of patients (30% +/- 7%). However, the bioavailability of the sachet was only 17% +/- 4% when administered with food. When the sachet was given to patients receiving ranitidine, no consistent change in bioavailability was noted. Also, no change in ddI pharmacokinetics was noted in patients receiving ganciclovir.

Acquired Immunodeficiency Syndrome↗

PubMed1979

The influence of food on the bioavailability of new formulations of erythromycin stearate and base.

1. The effect of food on the bioavailability of two new formulations of erythromycin, 1) erythromycin stearate, 500 mg (Erythrocin, 250 mg capsule-shaped tablets) and 2) erythromycin base, 500 mg (Eryc, 250 mg capsules containing enteric-coated pellets) was studied in 16 healthy subjects. 2. The study was a balanced, randomized Latin square design and was conducted on 4 days. The four treatments were erythromycin stearate immediately before (EB) and after EA) breakfast and erythromycin base immediately before (eB) and after (eA) breakfast. 3. The mean +/- s.d. maximal plasma erythromycin concentrations were 2.09 +/- 1.06, 0.37 +/- 0.40, 1.8+ +/- 1.15 and 1.91 +/- 1.57 micrograms/ml and the mean +/- s.d. times at which these occurred were 1.3 +/- 0.7, 2.3 +/- 0.9, 4.4 +/- 1.9 and 4.3 +/- 1.1 h for EB, EA, eB and eA respectively. 4. The mean +/- s.d. areas under the curves (0 to 8 h) were 4.99 +/- 2.41, 1.04 +/- 1.57, 4.93 +/- 2.98 and 4.98 +/- 3.14 for EB, EA, eB and eA respectively. 5. The bioavailability of erythromycin stearate was significantly reduced by the prior administration of food, whereas the absorption of the base was not inhibited by food.

Adult↗

PubMedDate not supplied

Comparison of two oral forms of erythromycin in the treatment of acute respiratory tract infections. A multicentre general practice study.

A total of 1244 patients with acute upper or lower respiratory tract infection were randomized to receive, twice daily for 7 days, either capsules of enteric-coated pellets of erythromycin base at a dose of 1 g/day or erythromycin ethylsuccinate tablets at a dose of 2 g/day in a single-blind, multicentre study. The efficacy of each formulation was similar, with about 90% of patients who had completed at least 5 days of treatment being reported as either cured or improved. Gastro-intestinal symptoms were the most commonly reported side-effects, being significantly more frequent in patients receiving erythromycin base. Gastro-intestinal intolerance was also the main reason for discontinuing either treatment, although it was a significantly more frequent reason in patients given erythromycin base. This study indicates that both formulations of erythromycin are highly effective for routine, empirical treatment of acute respiratory tract infections. Erythromycin base, however, appears to be less well tolerated than erythromycin ethylsuccinate.

Acute Disease↗

PubMed1993

Double-blind trial of steroid tapering in acute asthma.

It is customary to tail off the dose of oral steroids after treatment of an acute exacerbation of asthma; the main reason for this practice is to avoid rebound asthma. We have carried out a randomised double-blind study to find out whether a tapering course of oral prednisolone has any advantage over an abruptly terminated course of prednisolone for an episode of acute asthma requiring hospital admission. We studied 35 patients admitted to hospital with acute asthma; their mean peak expiratory flow rate (PEFR) on admission was 173 L/min and their mean age was 32 years (range 18-55); all were using inhaled steroids on discharge (mean dose 908 micrograms daily). Each patient received 40 mg enteric-coated prednisolone daily for 10 days followed by a tapering course of either prednisolone 5 mg tablets (active taper) or identical placebo tablets (placebo taper), reducing from 7 tablets on day 11 to no tablets by day 18. The primary outcome measure was the PEFR on waking. Both groups responded well to treatment by day 10 (mean morning PEFR: active taper group 396 L/min, placebo taper group 391 L/min). There was no further significant change in PEFR in either group during the 7 days of active or placebo tapering or during the following 10 days (repeated measures analysis of variance, active vs placebo, p = 0.82). The groups were also similar in terms of secondary outcome measures--symptom scores, PEFR after morning bronchodilator treatment, evening PEFR, and treatment failures. This study suggests that steroid tapering is unnecessary in acute asthma; a personal asthma management plan with a reserve course of prednisolone may be more appropriate.

Acute Disease↗

PubMed1983

Fasting and postprandial absorption of digoxin from a microencapsulated formulation.

The absorption of digoxin from a capsule preparation containing a large number of small, enteric-coated granules of the glycoside (Preparation CR) was compared in 10 volunteers with that from a rapidly dissolving tablet (Preparation L). Plasma and urine digoxin concentrations were measured by radioimmunoassay. In the fasting state, after a loading dose of digoxin (0.76 mg), peak plasma concentrations were significantly (p less than 0.001) lower after CR (2.0 +/- 0.5 nmol/l, mean +/- SD) than L (4.7 +/- 1.1 nmol/l). Peak concentrations after CR were significantly (p less than 0.001) delayed compared to L (3.3 +/- 0.6 h vs 1.1 +/- 0.4 h). Also, postprandial peak plasma concentrations at steady state, were significantly (p less than 0.01) lower after CR (1.0 +/- 0.3 nmol/l) than L (2.7 +/- 0.5 nmol/l), and the peak concentrations occurred later (3.9 +/- 1.7 h vs 1.4 +/- 0.9 h). The area under the plasma concentration-time curves was smaller (p less than 0.01) for CR (17.7 +/- 5.9 nmol X 1(-1) X h) than for L (22.4 +/- 4.1 nmol X 1(-1) X h), and so was the amount of drug excreted in urine (174 +/- 25 micrograms vs 190 +/- 31 micrograms; p less than 0.005). Thus, the absorption rate of digoxin from the enteric-coated formulation was markedly reduced but at the cost of a variable reduction in the amount absorbed.

Adult↗

PubMed1993

A reevaluation of aspirin therapy in rheumatoid arthritis.

BACKGROUND: Aspirin therapy has been largely superseded by prescription nonsteroidal anti-inflammatory drug (NSAID) therapy in rheumatoid arthritis, in part because of premarketing studies suggesting lesser toxic effects for NSAIDs than for aspirin. This study evaluates these toxic effects in a postmarketing population of patients with rheumatoid arthritis. METHODS: We studied 1521 consecutive courses of aspirin and 4860 courses of NSAIDs in patients with rheumatoid arthritis from eight Arthritis, Rheumatism, and Aging Medical Information System Post-marketing Surveillance Centers. Toxicity index scores were generated from symptoms, laboratory abnormalities, and hospitalizations, weighted for variable severity and severity of side effect. RESULTS: The toxicity index was only 1.37 (SE = 0.10) for aspirin and 1.87 to 2.90 for selected nonsalicylate NSAIDs. These differences were consistent across centers and remained after statistical adjustment for differing patient characteristics. There was a different toxicity with different aspirin preparations, with a score for plain aspirin of 1.36 (SE = 0.23), for buffered aspirin of 1.10 (0.20), and for enteric-coated aspirin preparations of 0.92 (0.14). Most important, there were strong dose effects, with a score of 0.73 (0.09) for 651 to 2600 mg daily, 1.08 (0.17) for 2601 to 3900 mg, and 1.91 (0.38) for more than 3900 mg. The average aspirin dose taken was only 2665 mg/d, approximately eight "tablets," compared with 3600 to 4800 mg/d used in the 16 pivotal premarketing studies reviewed. Average NSAID doses were, on the other hand, lower in premarketing trials (eg, naproxen 500 mg/d vs 773 mg/d in the Arthritis, Rheumatism, and Aging Medical System clinical practices). CONCLUSIONS: Aspirin therapy, in doses commonly employed in practice, has an excellent safety profile in rheumatoid arthritis, and it is the least costly NSAID. The safety advantage is explained primarily by a dose effect and secondarily by possible differences between formulations. Newer management strategies for rheumatoid arthritis emphasize NSAID use as symptomatic therapy and use of disease-modifying anti-rheumatic drug therapy for anti-inflammatory objectives. Thus, the original recommendation for "anti-inflammatory" doses of aspirin now is less easily justified. Aspirin therapy merits reconsideration as adjunctive therapy for the management of rheumatoid arthritis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1988

Randomised trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 cases of suspected acute myocardial infarction: ISIS-2. ISIS-2 (Second International Study of Infarct Survival) Collaborative Group.

17,187 patients entering 417 hospitals up to 24 hours (median 5 hours) after the onset of suspected acute myocardial infarction were randomised, with placebo control, between: (i) a 1-hour intravenous infusion of 1.5 MU of streptokinase; (ii) one month of 160 mg/day enteric-coated aspirin; (iii) both active treatments; or (iv) neither. Streptokinase alone and aspirin alone each produced a highly significant reduction in 5-week vascular mortality: 791/8592 (9.2%) among patients allocated streptokinase infusion vs 1029/8595 (12.0%) among those allocated placebo infusion (odds reduction: 25% SD 4; 2p less than 0.00001); 804/8587 (9.4%) vascular deaths among patients allocated aspirin tablets vs 1016/8600 (11.8%) among those allocated placebo tablets (odds reduction: 23% SD 4; 2p less than 0.00001). The combination of streptokinase and aspirin was significantly (2p less than 0.0001) better than either agent alone. Their separate effects on vascular deaths appeared to be additive: 343/4292 (8.0%) among patients allocated both active agents vs 568/4300 (13.2%) among those allocated neither (odds reduction: 42% SD 5; 95% confidence limits 34-50%). There was evidence of benefit from each agent even for patients treated late after pain onset (odds reductions at 0-4, 5-12, and 13-24 hours: 35% SD 6, 16% SD 7, and 21% SD 12 for streptokinase alone; 25% SD 7, 21% SD 7, and 21% SD 12 for aspirin alone; and 53% SD 8, 32% SD 9, and 38% SD 15 for the combination of streptokinase and aspirin). Streptokinase was associated with an excess of bleeds requiring transfusion (0.5% vs 0.2%) and of confirmed cerebral haemorrhage (0.1% vs 0.0%), but with fewer other strokes (0.6% vs 0.8%). These "other" strokes may have included a few undiagnosed cerebral haemorrhages, but still there was no increase in total strokes (0.7% streptokinase vs 0.8% placebo infusion). Aspirin significantly reduced non-fatal reinfarction (1.0% vs 2.0%) and non-fatal stroke (0.3% vs 0.6%), and was not associated with any significant increase in cerebral haemorrhage or in bleeds requiring transfusion. An excess of non-fatal reinfarction was reported when streptokinase was used alone, but this appeared to be entirely avoided by the addition of aspirin. Those allocated the combination of streptokinase and aspirin had significantly fewer reinfarctions (1.8% vs 2.9%), strokes (0.6% vs 1.1%), and deaths (8.0% vs 13.2%) than those allocated neither. The differences in vascular and in all-cause mortality produced by streptokinase and by aspirin remain highly significant (2p less than 0.001 for each) after the median of 15 months of follow-up thus far available.

Administration, Oral↗

PubMed1988

Randomized trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 cases of suspected acute myocardial infarction: ISIS-2.ISIS-2 (Second International Study of Infarct Survival) Collaborative Group.

17,187 patients entering 417 hospitals up to 24 h (median 5 h) after the onset of suspected acute myocardial infarction were randomized, with placebo control, between i) a 1 h intravenous infusion of 1.5 million units of streptokinase; ii) 1 month of 160 mg/day enteric-coated aspirin; iii) both active treatments; or iv) neither. Streptokinase alone and aspirin alone each produced a highly significant reduction in 5 week vascular mortality: 791/8592 (9.2%) vascular deaths among patients allocated streptokinase infusion versus 1029/8595 (12.0%) among those allocated placebo infusion (odds reduction: 25% +/- 4; 2p less than 0.00001); 804/8587 (9.4%) vascular deaths among patients allocated aspirin tablets versus 1016/8600 (11.8%) among those allocated placebo tablets (odds reduction: 23% +/- 4; 2p less than 0.00001). The combination of streptokinase and aspirin was significantly (2p less than 0.0001) better than either agent alone. Their separate effects on vascular death appeared to be additive: 343/4292 (8.0%) among patients allocated both active agents versus 568/4300 (13.2%) among those allocated neither (odds reduction: 42% +/- 5; 95% confidence limits 34% to 50%). There was evidence of benefit rom each agent even for patients treated late after pain onset (odds reduction at 0-4, 5-12, and 13-24 h: 35% +/- 6, 16% +/- 7 and 21% +/- 12 for streptokinase alone; 25% +/- 7,21% +/- 7 and 21% +/- 12 for aspirin alone; and 53% +/- 8,32% +/- 9 and 38% +/- 15 for the combination of streptokinase and aspirin). Streptokinase was associated with an excess of bleeds requiring transfusion (0.5% versus 0.2%) and of confirmed cerebral hemorrhage (0.1% versus 0.0%), but with fewer other strokes (0.6% versus 0.8%). These "other" strokes may have included a few undiagnosed cerebral hemorrhages, but still there was no increase in total strokes (0.7% streptokinase versus 0.8% placebo infusion). Aspirin significantly reduced nonfatal reinfarction (1.0% versus 2.0%) and nonfatal stroke (0.3% versus 0.6%), and was not associated with any significant increase in cerebral hemorrhage or in bleeds requiring transfusion. An excess of nonfatal reinfarction was reported when streptokinase was used alone, but this appeared to be entirely avoided by the addition of aspirin. Those allocated the combination of streptokinase and aspirin had significantly fewer reinfarctions (1.8% versus 2.9%), strokes (0.6% versus 1.1%), and deaths (8.0% versus 13.2%) than those allocated neither.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMedDate not supplied

Pharmacokinetic evaluation of para-aminosalicylic acid granules.

STUDY OBJECTIVE: To determine the bioavailability and renal elimination of para-aminosalicylic acid (PAS) and its inactive metabolite acetyl-para-aminosalicylic acid (AcPAS) from a new PAS formulation. DESIGN: (a) Single-dose pharmacokinetic study in healthy volunteers; (b) Day-1 and day-8 pharmacokinetic comparison in patients with multidrug-resistant tuberculosis (MDR-TB). SETTING: Referral hospital that specializes in the treatment of mycobacterial infections. PATIENTS: (a) Twelve healthy male and female volunteers recruited by the investigators. Eleven subjects (92%) completed the study; one subject could not maintain venous access and was removed from the study. (b) Six sequential male and female patients receiving multidrug treatment for advanced MDR-TB. All patients completed the study. INTERVENTIONS: (a) Volunteers received a single 4-g dose of enteric-coated PAS granules administered with food. Blood and urine samples were collected over 24 hours after the dose. (b) Patients received 4-g doses of enteric-coated PAS granules every 8 hours for 7 days as part of their treatment regimen. Blood samples were obtained at approximately 2, 4, and 8 hours after the first dose on day 1 and the twenty-second dose on day 8. MEASUREMENTS AND MAIN RESULTS: Concentrations of PAS and AcPAS were determined using high-performance liquid chromatography. The serum concentration-time curves from volunteers and patients showed sustained PAS concentrations, in contrast to immediate-release sodium PAS tablets. In the six patients with tuberculosis, day 8 concentrations were considerably higher than those on day 1, and all were sustained well above the PAS minimal inhibitory concentration for Mycobacterium tuberculosis. CONCLUSIONS: Para-aminosalicylic acid granules produce adequate serum concentrations and appear to be safe.

Absorption↗

PubMed1988

Use of pancreatic Schilling test to determine efficiency of pancreatic enzyme delivery in pancreatic insufficiency.

The pancreatic Schilling test (PST), a noninvasive, sensitive pancreatic function test, was studied to determine its ability to detect pancreatic proteolytic enzyme replacement in patients with pancreatic insufficiency. Seven subjects with well-documented pancreatic insufficiency and an abnormal PST consistent with pancreatic insufficiency were studied with three enzyme regimens: (1) Viokase (four tablets), (2) Pancrease (three capsules), and (3) Pancrease (10 capsules). The effect of cimetidine on the results of the PST with high-dose Pancrease was also determined in two subjects with pancreatic insufficiency and in two normal volunteers. The results of the investigation demonstrate that the PST is a sensitive noninvasive test for the presence of orally administered proteolytic enzymes in subjects with pancreatic insufficiency and in normals. Furthermore, the studies illustrate that the administration of enzymes in a form of enteric-coated microspheres does not enhance the delivery of proteolytic enzymes to the small intestine when compared to conventional high-dose enzyme replacement. Cimetidine appears to decrease the inactivation of the proteolytic enzymes in enteric-coated microspheres, suggesting that a low pH in the small intestine and stomach are responsible for the poor delivery of the enzymes into the small intestine.

Adult↗

PubMed1990

Gastrointestinal behavior of orally administered radiolabeled erythromycin pellets in man as determined by gamma scintigraphy.

The behavior of single 250-mg doses of a multiparticulate form of erythromycin base (ERYC(R)), each including five pellets radiolabeled with neutron-activated samarium-153, was observed by gamma scintigraphy in seven male subjects under fasting and nonfasting conditions. The residence time and locus of radiolabeled pellets within regions of the gastrointestinal tract were determined and were correlated with plasma concentrations of erythromycin at coincident time points. Administration of food 30 minutes postdosing reduced fasting plasma erythromycin Cmax and area under the plasma erythromycin versus time curve (AUC) values by 43% and 54%, respectively. Mean peak plasma concentration of erythromycin (Cmax) in the fasting state was 1.64 micrograms/mL versus 0.94 micrograms/mL in the nonfasting state. Total oral bioavailability, as determined by mean AUC (0-infinity) of the plasma erythromycin concentration versus time curve, was 7.6 hr/micrograms/mL in the fasted state, versus 3.5 hr/micrograms/mL in the nonfasting state. Mean time to peak plasma erythromycin concentration (tmax) in the fasting state was 3.3 hours, versus 2.3 hours in the nonfasting state. Plasma concentrations of erythromycin in both fasting and nonfasting states were within acceptable therapeutic ranges. Evidence provided by this study: 1) indicates that pellet erosion and absorption of active erythromycin base begins when the enteric-coated pellets reach the highly vascular mucosa of the jejunum and proximal ileum, and is essentially completed within the ileum, with a significant portion absorbed in the medial-to-distal ileum; 2) confirms that acceptable therapeutic plasma levels of erythromycin are attained in nonfasting subjects (Cmax = 0.94 microgram/mL) and that superior plasma erythromycin concentrations (Cmax = 1.64 micrograms/mL) are achieved by administration of the dose on an empty stomach 1 to 2 hours before or after meals; 3) corroborates other comparative studies reporting greater fasting bioavailability with this multiparticulate dosage form of erythromycin base than with reference single tablet or particle-in-tablet formulations; and 4) indicates that neutron activation of stable isotopes incorporated as a normal excipient in industrially-produced formulations provides an effective means for in vivo evaluation of dosage forms through gamma scintigraphy.

Administration, Oral↗

PubMed1985

Aspirin kinetics and inhibition of platelet thromboxane generation-relevance for a solution of the "aspirin dilemma".

Six healthy male volunteers received aspirin (ASA) in a compressed (320 mg) and an enteric-coated (800 mg) formulation as single oral doses ten days apart. Ten plasma samples were obtained from each volunteer between 5 and 120 min after compressed ASA, and seven between 10 and 240 min after enteric-coated ASA. ASA was undetectable (less than 100 ng/ml) in plasma from three subjects receiving compressed ASA and two receiving the enteric-coated preparation. Plasma levels and kinetic parameters of salicylate were the same in subjects with undetectable and detectable ASA plasma levels. More than 98% inhibition of pre-drug serum TXB2 was noted in all samples collected one and four hours after either ASA preparation. TXB2 generation recovered on average by 3.5% at 24 hr with both preparations. Thus inhibition of platelet TXB2 generation occurred independently of the amount of ASA reaching the peripheral circulation. If this is due to inhibition of platelet function in the enterohepatic circulation followed by extensive first-pass deacetylation of ASA, vascular PGI2 synthesis could be spared. A better knowledge of the kinetic parameters of ASA for each of the formulations used in thrombosis prevention trials might help in solving the "aspirin dilemma".

Adult↗

PubMed1990

Gastrointestinal transit of nondisintegrating, nonerodible oral dosage forms in pigs.

Gastrointestinal (GI) transit data necessary as "baseline" or "control" information were collected using pigs as animal models preliminary to bioavailability studies of new sustained action formulations. Density and size effects of nondisintegrating dosage forms on GI transit were investigated. Initially, enteric-coated nondisintegrating magnesium hydroxide caplets (density, 1.5 g/ml; size, 19.6 x 9.5 mm; weight, 1.2 g) were utilized in seven pigs. Prolonged gastric residence (greater than 5 days) occurred in every case for this dosage form. Therefore, nondisintegrating caplets of three densities (1.25, 1.45, and 2.3 g/ml) and three different sizes (large, 20 x 10 mm; medium, 10 x 10 mm; small, 5 x 10 mm) were studied in two more pigs. Roentgenography was used to visualize passage of caplets through the GI tract. Heidelberg pH capsules (size, 8 x 20 mm; density, 1.61 g/ml) were also used in this study. Total GI transit times range from 2 to 33 days for 22 administrations of these nondisintegrating dosage forms. Pigs are found to not be an appropriate model for evaluating bioavailability of nondisintegrating controlled-release dosage forms because total GI transit time (especially gastric transit) is much too long.

Animals↗

PubMed1991

Calcium carbonate as a phosphate binder in dialysis patients: evaluation of an enteric-coated preparation and effect of additional aluminium hydroxide on hyperaluminaemia.

Calcium carbonate has been successfully used as a phosphate binder in patients with chronic renal failure; however, a high frequency of hypercalcaemia has been reported. To study the effects of calcium carbonate preparations with different dissolution characteristics on the incidence of this side effect, we conducted a double-blind, crossover trial in 21 patients undergoing chronic haemodialysis. Aluminum hydroxide therapy was replaced with calcium carbonate. The subjects then randomly received either an enteric-coated or a gastric-coated preparation. Calcium carbonate (3.1-3.6 g/d) controlled serum phosphate concentrations as effectively as aluminium hydroxide (2.9 g/d). Concurrently, there was a significant rise in mean serum calcium and a fall in serum concentrations of both parathyroid hormone and osteocalcin, the latter suggesting a decrease in bone turnover. Overall, hypercalcaemic episodes developed in 9 patients (43%) and occurred at a considerable frequency (33 episodes per 100 patient-months) during treatment with the gastric-coated formulation. Following conversion to enteric-coated calcium carbonate (3.6 g/d) patients had fewer occurrences of hypercalcaemia (12 episodes per 100 patient-months, P less than 0.05) and, as compared to the gastric-coated preparation, increases in serum calcium greater than 3.00 mmol/l were not observed at all. Hyperaluminaemia was regressive during therapy with calcium carbonate, but addition of small doses of aluminium hydroxide caused a large rise in serum aluminium concentrations after infusion of desferrioxamine, indicating an enhanced rate of absorption or aberrant compartmentalization of aluminium. We conclude that calcium carbonate can control hyperphosphataemia in dialysis patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗