Pharmacokinetics and relative bioavailability of a new chewable, buffered acetylsalicylic acid tablet formulation in comparison to a conventional plain tablet.

The pharmacokinetics of acetylsalicylic acid (ASA) and its main metabolite salicylic acid (SA) following single dose administration of a new chewable, buffered ASA tablet formulation and a conventional plain ASA tablet formulation were investigated in 12 healthy male subjects. The volunteers received in a randomized, crossover design two pharmaceutical units of both formulations containing 500 mg ASA each after an overnight fast on an empty stomach. ASA and SA in the collected plasma and urine samples were determined using an internally standardized validated HPLC method. Regarding the normalized extent parameters for ASA, an increase of about 114% for the maximum concentration (Cmax,norm) and about 16% for the area under the curve (AUC0----infinity,norm) was found for the new chewable, buffered tablet formulation as compared to the plain tablet. Comparing the corresponding parameters for the main metabolite, both formulations were statistically equivalent. The quotient of normalized areas (QAUC0-20min, norm/AUC0----infinity,norm) for ASA was higher by about 124% for the new formulation, indicating an increased and faster absorption during the first 20 min after administration. The time of the concentration maximum did not differ statistically. These data indicate that the new chewable, buffered ASA tablet formulation shows a significant benefit as compared to the plain ASA tablet. The new tablet produced higher plasma ASA concentrations in a shorter time, which is clinically important since higher ASA concentrations are assumed to be related to an improved analgesic efficacy.     

Pharmacokinetics of ketoconazole administered intravenously to dogs and orally as tablet and solution to humans and dogs

The single-dose pharmacokinetics and bioavailability of three ketoconazole formulations were evaluated using HPLC in five healthy human volunteers and six male mongrel dogs. The human volunteers received 400 mg po of ketoconazole as tablet (Ktab) and solution (Ksol) formulations. The dogs received 400 mg po of Ktab and Ksol, and 376 mg iv of an intravenous dose (Kiv). In humans the AUC value for Ksol (62.21 +/- 21.2 microgram X h/ml; mean +/- SD) was significantly greater than for Ktab (50.0 +/- 15.2 micrograms X h/ml; p less than 0.05). Peak serum concentrations (Cmax), time to peak serum concentrations (tmax), t1/2, and the terminal elimination rate constant (kel) did not differ between Ktab and Ksol. This suggests that the administration of Ksol may be a useful alternative to dosage increases in situations where low bioavailability of ketoconazole in tablet form is suspected. The mean systemic clearance (CLs) of Kiv in dogs was 2.74 +/- 1.10 mL/min/kg, the volume of distribution at steady state (Vdss) was 0.72 +/- 0.28 L/kg, and the half-life was 2.7 +/- 1.6 h. Considerable variability was seen in the AUC of ketoconazole, particularly with the oral preparations. The absolute bioavailability of Ktab was 0.50 +/- 0.38, which did not differ statistically from that of Ksol, 0.56 +/- 0.23. The Ksol showed less variability in AUC, Cmax, and F values than did Ktab, and two dogs with low bioavailability with Ktab (0.04 and 0.07) had substantially greater bioavailability with Ksol (F = 0.96 and 0.57, respectively). Evaluation of Kiv in dogs confirms decreased bioavailability from orally administered tablet formulations of ketoconazole.     

Pharmacokinetic profiles of two tablet formulations of piroxicam

There is considerable interest in developing new non-steroidal anti-inflammatory drugs (NSAIDs) formulations with faster onset of analgesic action like fast dissolving tablets. An open-label, randomized, single dose, crossover study with a 18 days washout period was conducted in 16 healthy volunteers to compare the pharmacokinetic profile of 20 mg piroxicam freeze-dried tablet (Proxalyoc, Cephalon) with that of 20 mg piroxicam capsule (Feldene, Pfizer). T(lag) with freeze-dried tablet was three times shorter than with capsule (21.6 min versus 59.4 min). Mean AUC(0-30 min), mean AUC(0-1 h), mean plasma concentrations at 15 min, 30 min and 1 h post-dose were significantly higher with the freeze-dried tablet than with the capsule, indicating that piroxicam was more rapidly absorbed from the freeze-dried tablet with higher plasma concentrations achieved at shorter intervals after dosing. The 90% confidence intervals of the ratios of means C(max), AUC(0-t), AUC(0-infinity) and T(1/2) all fell within the acceptance range of 0.8-1.25, demonstrating the bioequivalence of the two formulations. Although the bioavailability of the two formulations was similar, the administration of piroxicam as a freeze-dried tablet gave a much faster absorption rate during the first hour after dosing than the capsule formulation. This faster absorption is an obvious advantage for the treatment of acute episodes of pain.     

Systemic Availability of Acetylsalicylic Acid in Human Subjects after Oral Ingestion of Three Different Formulations

Abstract: Systemic availability of acetylsalicylic acid (ASA) in normal human subjects after oral ingestion of 1 g in three different formulations was determined by using high-pressure liquid chromatography for ASA assay. For an effervescent, a plain and a sustained release preparation systemic availabilities expressed in percent of the ingested dose were 16.9±3.2, 8.6±1.2 and 2.6±0.4%, respectively. All subjects had clearly measureable amounts of ASA in plasma after oral intake of a sustained release preparation with an average peak concentration of 15 μmol/1. Peak concentration after an effervescent and plain formulation was on the average 80 and 40 μmol/1, respectively. Half-life of ASA in plasma was 18.1±1.2 min. for the effervescent and 28.7±5.3 min. for the plain preparation, while the elimination phase was too ill defined for the sustained release formulation. Average plasma half-life of salicylic acid (SA) was similar after the three different administration forms with values between 3.0 and 3.7 hrs. Further, no difference in SA distribution volumes or amounts of SA absorbed was found. The present study demonstrates that oral ingestion of ASA in effervescent, plain and sustained release formulations gives rise to significant amounts of ASA in plasma. Concentrations found indicate that long-term antithrombotic therapy with ASA in a sustained release formulation may be possible.     

Bioequivalence study of levofloxacin tablets in healthy Indian volunteers using HPLC

An improved HPLC method was developed and validated for the determination of concentration of levofloxacin (CAS 100986-85-4) in human plasma. This paper is an attempt to compare the bioavailability of two levofloxacin tablet formulations (reference and test) containing 500 mg of levofloxacin. Both the formulations were administered orally as a single dose, separated by a washout period of 1 week. The HPLC method was validated by examining the precision and accuracy for the inter-day and intra-day runs in a linear concentration range of 0.10-10.00 microg/ml. Bioequivalence of two formulations were determined in 12 healthy, Indian, male volunteers in a single-dose, two-period, two-sequence, two-treatment crossover study. The content of levofloxacin in plasma was determined using HPLC with UV detection. The formulations were compared using the following pharmacokinetic parameters: area under the plasma concentration-time curve (AUC(o-t)), area under the plasma concentration-time curve from zero to infinity (AUC(o-infinity)), peak plasma concentration (C(max)), and time to reach peak plasma concentration (t(max)). The results indicated that there were no statistically significant differences (P > 0.05) between the logarithmically transformed AUC(o-infinity), and C(max) values of the test and reference formulations. The 90% confidence interval for the ratio of the logarithmically transformed AUC(o-t), AUC(o-infinity) and C(max) were within the bioequivalence limit of 0.8-1.25 and the relative bioavailability of the test formulation was 99.98% of that of the reference formulation.     

Pharmacokinetics and gamma scintigraphy evaluation of two enteric coated formulations of didanosine in healthy volunteers

AIMS: The aims of the study were to evaluate the bioavailability of didanosine from the encapsulated enteric coated beads (1 x 200 mg; enteric beads) and enteric coated mini-tablets (4 x 50 mg; enteric tablet) formulations relative to the chewable/dispersible buffered tablets (2 x 100 mg; buffered tablet), and to study their rate of gastrointestinal transit. METHODS: This was a single-dose, randomized, three-way crossover study in 18 healthy male volunteers. A 200 mg dose of didanosine was given in each period and each formulation contained a gamma radiation-emitting isotope. Pharmacokinetic parameters determined were Cmax, tmax, AUC(0, infinity ) and t1/2. Bioequivalence was assessed using the confidence interval (CI) of 0.80, 1.25 for Cmax and AUC(0, infinity ). Scintigraphic images were recorded and gastrointestinal transit profiles were generated. RESULTS: The point estimate and 90% CI of the ratio of Cmax for the enteric beads and enteric tablet relative to the buffered tablet was 0.71 (0.59, 0.85) and 0.55 (0.46, 0.66), respectively. The tmax was significantly different for the enteric beads (median, 1.33 h) and the enteric tablet (median, 2.83 h) than for the buffered tablet (median, 0.67 h). The AUC(0, infinity ) satisfied the bioequivalence criteria, and the point estimate and 90% CI of the ratio were 1.02 (0.91, 1.15) and 0.92 (0.82, 1.04) for the enteric beads and enteric tablet, respectively. The AUC(0, infinity ) values appeared to be less variable with the enteric beads (% CV = 19%) than with the enteric tablet (% CV = 33%). The t1/2 values were not significantly different between formulations, and the mean values ranged from 1.82 to 1.92 h. Inspection of the individual scintigraphy profiles and concentration-time curves suggested that didanosine was absorbed throughout the small intestine. Gastrointestinal transit parameters were higher for both enteric formulations than for the buffered tablet, indicating slower transit of the enteric formulations. Between the enteric formulations, gastric emptying was slower for the enteric beads than for the enteric tablet; however, plasma didanosine concentrations were observed sooner for the enteric beads, suggesting that the enteric coat for the beads dissolved more rapidly. CONCLUSIONS: The enteric beads and enteric tablet formulations of didanosine were equivalent to the buffered tablet in their extent of absorption. Although the gastric emptying of the enteric tablet was faster, based on the rapid uncoating and the lower variability in AUC, the enteric beads were chosen for further clinical development.     

Application of a radiotelemetric system to evaluate the performance of enteric coated and plain aspirin tablets

The bioavailability of enteric coated and plain aspirin tablets was studied in four beagle dogs. Blood sampling for enteric coated tablets was planned with the aid of a radiotelemetric system. The release of aspirin from its dosage form was detected by monitoring the change in intestinal pH. Aspirin and salicylic acid levels in plasma obtained from the enteric coated dosage form exhibited familiar concentration versus time absorption profiles. Variation in the plasma concentrations of these two compounds within each dog studied (four runs each) was relatively small when time zero was adjusted to the commencement of tablet dissolution. The plasma levels obtained from plain aspirin (three runs each), however, show atypical absorption. The estimated absolute bioavailability was 0.432 +/- 0.0213 and 0.527 +/- 0.0260 for enteric coated and plain aspirin, respectively. Other pharmacokinetic parameters for these two dosage forms such as the highest observed plasma concentration (Cmax) (10.9 +/- 0.535 microgram/mL versus 13.6 +/- 1.88 micrograms/mL) and the time to reach Cmax (tmax) (26.6 +/- 1.94 min versus 31.0 +/- 7.04 min) agree well. The mean values for gastric emptying time, in vivo coating dissolution time, and in vivo disintegration/dissolution time of the tablet core for enteric coated aspirin are 48.7 +/- 7.23 min, 44.3 +/- 3.80 min, and 34.7 +/- 2.04 min, respectively.     

Effect of food and relative bioavailability following single doses of diclofenac 150 mg hydrogel bead (HGB) capsules in healthy humans.

The effect of food on the bioavailability of diclofenac from a 150 mg diclofenac hydrogel bead (HGB) capsule was evaluated in 12 healthy male subjects in a fed and fasted state. Additionally, the fasting bioavailability of diclofenac from a 150 mg diclofenac HGB capsule relative to diclofenac sodium in buffered aqueous solution was evaluated in these same 12 subjects. The study was designed as an open-label, randomized, single-dose, 3 x 3 Latin-square crossover trial balanced for residual effects. A 2-week washout period was maintained between treatments. Blood samples were collected at frequent intervals over a 24-h period with plasma being separated and analyzed for diclofenac using a validated HPLC method. The administration of the 150 mg diclofenac HGB capsule dose within 30 min following a standardized breakfast minimally affected the bioavailability of diclofenac relative to administration under fasted conditions (7 per cent decrease in AUC(0-24), p greater than 0.05). There was, however, a 38 per cent decrease (p less than 0.05) in the Cmax and a three-fold increase (p less than 0.05) in Tmax for the fed HGB capsule administration. Under fasted conditions, significant differences in mean pharmacokinetic parameters were found between the 150 mg diclofenac HGB capsule and diclofenac sodium in buffered aqueous solution. The extent of availability of diclofenac from the HGB capsule was only 59 per cent relative to that from the solution (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Gastric potential difference measurement as a quantification of gastrointestinal tolerability comparing a buffered acetylsalicylic acid formulation versus plain acetylsalicylic acid.

Two different acetylsalicylic acid (ASA, CAS 50-78-2) formulations (Aspirin) were compared regarding their gastric mucosal tolerability. After administration of plain ASA, buffered ASA and ASA placebo the decrease of gastric potential difference (GPD) was measured. Evaluation of the GPD parameters showed a better tolerability of buffered ASA than of plain ASA. It was therefore concluded that buffered ASA effects less gastric mucosal irritation than plain ASA.     

2种佐米曲普坦制剂人体生物等效性研究

目的:比较国产佐米曲普坦胶囊与进口佐米曲普坦片剂的人体生物等效性。方法:18名志愿者随机交叉单次口服佐米曲普坦胶囊或片剂10mg后,采用高效液相色谱法测定血药浓度,用3p97软件包计算二者的药动学参数和生物等效性。结果:胶囊与片剂的药-时曲线均为口服吸收一室摸型。t1/2ke分别为(3.72±1.77)、(3.81±1.44)h,tmax分别为(1.42±0.35)、(1.33±0.51)h,Cmax分别为(21.68±8.67)、(21.86±10.38)μg/L,AUC(0～T)分别为(75.94±31.34)、(78.40±28.21)(μg.h)/L。佐米曲普坦胶囊的相对生物利用度为(96.86±13.36)%,经方差分析、双单侧t检验及(1～2α)置信区间法统计分析,2种制剂药动学参数无显著性差异(P>0.05)。结论:佐米曲普坦胶囊与片剂具有生物等效性。     

Relative bioavailability of three cefixime formulations

Three galenic formulations of cefixime (tablet, syrup and dry suspension) containing 200 mg each were compared with respect to their relative bioavailability in twelve healthy volunteers. All three formulations showed reliable absorption. Mean peak plasma concentrations were reached after 3.3-3.5 h, mean terminal half lives were 2.9-3.1 h. 18-24% of the dose administered were recovered unchanged in the urine. Best bioavailability was obtained with the dry suspension (AUC0-infinity = 25.8 +/- 7.0 micrograms/ml h; Cmax = 3.4 +/- 0.9 microgram/ml), followed by the tablet (AUC0-infinity = 20.9 +/- 8.1 micrograms/ml h; Cmax = 3.0 +/- 1.0 micrograms/ml) and the syrup which is based on triglycerides (AUC0-infinity = 17.8 +/- 5.9 micrograms/ml h; Cmax = 2.4 +/- 0.7 micrograms/ml). The statistical analysis resulted in bioinequivalence between dry suspension and syrup. It is concluded that best bioavailability of cefixime after oral administration is guaranteed when taken in an "aqueous medium" either as dry suspension or as tablet with "plenty of liquid".     

Comparison of high pressure liquid chromatography and fluorescence polarization immunoassay to assess quinidine pharmacokinetics

High pressure liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA) were compared in a quinidine pharmacokinetic study. Six healthy male subjects received single oral doses of regular release (RR) quinidine sulfate, sustained release (SR) quinidine bisulfate and the same dose of the SR product with food (SR-F). Serum was collected for 49 h after each dose and analysed for quinidine by HPLC and FPIA. Using HPLC, there were no statistically significant differences between dosing regimens with respect to area under the curve (AUC) or terminal rate constant (K). The RR dose resulted in a higher peak plasma concentration (Cp) and shorter time to peak (Tp) than either of the SR doses (p less than 0.01). Food had no apparent effect on the bioavailability of the SR product. When using FPIA, food administration was found to increase the AUC for the SR product (p less than 0.05) and all three dosage regimens resulted in a different Cp and Tp (p less than 0.001). When comparing all pharmacokinetic parameters determined by each assay, FPIA resulted in a significantly lower K (p less than 0.01). Orthogonal regression of all serum quinidine concentrations showed that FPIA = 0.926 (HPLC) + 0.06 (r = 0.971, p less than 0.001). Analysis of quinidine concentrations in different concentration ranges revealed that FPIA overestimated HPLC for concentrations less than 1 micrograms ml-1 (p less than 0.001) and underestimated HPLC for concentrations greater than 2 micrograms ml-1 (p less than 0.01). Although the use of FPIA is appropriate for quinidine therapeutic drug monitoring, HPLC is the preferred assay method for assessing pharmacokinetic parameters in single dose bioavailability studies.     

Relative bioavailability of rimantadine HCl tablet and syrup formulations in healthy subjects

Twenty healthy male subjects completed an open-label randomized crossover design to assess the bioavailability of 100 mg of rimantadine HCl in tablet and syrup forms relative to an oral solution. Blood samples were drawn and rimantadine plasma concentrations were determined by a GC-MS method. The maximum plasma concentration (Cmax), the time to Cmax (tmax), the area under the plasma concentration-time curve (AUC), and k were compared among treatments using an analysis of variance and the Hauck-Anderson test for bioequivalence. The Hauck-Anderson test was satisfied when the syrup and solution were compared. The relative bioavailability of the syrup was 96%. Both Cmax and AUC were significantly (p less than 0.05) increased (23 and 17%, respectively) when the tablet was compared with the solution. The relative bioavailability of the tablet was 117%. This outcome was unusual and could not be explained. However, this was not anticipated to be of clinical consequence since the majority of the safety and efficacy of rimantadine HCl was established using a tablet.     

Evaluation of the absorption from three ibuprofen formulations

The pharmacokinetic differences between two sustained-release 300 mg (A) and 400 mg (B) formulations and a rapid-release 400 mg ibuprofen conventional sugar-coated formulation (C) were compared after a single dose. Mean peak levels of 25.1 micrograms/ml for preparation A (2 X 300 mg), 31.3 micrograms/ml for preparation B (2 X 400 mg) and 68.5 micrograms/ml for preparation C (2 X 400 mg) were reached at 5.3, 3 and 2 hours respectively, after ingestion of the drugs. The individual plasma-level time-profiles for the majority of doses suggested prolonged absorption of product A and B. The absorption from formulations A and B was significantly slower (p less than 0.001 and p less than 0.05 respectively) than that from the conventional tablets. The bioavailability of ibuprofen from sustained-release capsules, was not found to differ significantly from that of ibuprofen from conventional tablets. The relative bioavailability was very close to 100% in almost all subjects (coefficient of variation 14% and 17%). Projections of plasma concentrations upon multiple dosing were made from single dose data. The dosage interval concentration ratio which reflects both the frequency and the entry of the drug into and from the body was much lower for sustained-release formulations (A: 3.0; B: 3.7; C: 12.9).     

多剂量萘普生缓释片及普通片的人体药代动力学和生物利用度研究

８名健康男性受试者连续６ｄ多剂量交叉口服萘普生缓释片和普通片的药代动力学和相对生物利用度研究。结果表明：萘普生缓释片和普通片的Ｔｍａｘ分别为３．５ｈ和１．３ｈ,表明缓释效果明显;经统计分析,萘普生缓释片（５００ｍｇ,ｑｄ）与萘普生普通片（２５０ｍｇ,ｂｉｄ）生物等效;萘普生缓释片的相对生物利用度为９７．０％;２种制剂的其他药代动力学参数如Ｃｍａｘ、Ｃｍｉｎ、ＡＵＣ２４０、ＡＵＣ∞０、ｔ１／２以及波动系数（ＦＩ）等均无显著性差异。     

甘氨酸茶碱钠缓释片与普通片药物动力学对比

采用一步液液提取反相高效液相色谱法对甘氨酸茶碱钠缓释片 (受试制剂 )与普通片 (参比制剂 )在人体内药物动力学行为进行了对比检测 ,绘制了 12名健康男性志愿受试者分别单剂量和多剂量随机交叉口服上述两种制剂后的茶碱血浆浓度 时间曲线并计算主要的药动学参数 .经统计检验 ,两种制剂的AUC无显著性差异 .单剂量和多剂量口服甘氨酸茶碱钠缓释片的相对生物利用度分别为 (91.7± 16 .8) %和 (10 7.5± 18.6 ) % .与普通片相比 ,甘氨酸茶碱钠缓释片的Cmax较低 ,而Cmin较高 ,Tmax明显滞后 ,MRT延长 ,血药浓度波动幅度显著减小 ,符合缓释制剂的特点 ,可较为安全地应用于临床 .     

Pharmacokinetic evaluation of conventional and controlled release dosage form of propranolol

A comparative pharmacokinetic study of a new controlled release multiple unit propranolol formulation and a conventional propranolol tablet was carried out in twelve healthy human volunteers in a randomized balanced crossover design. Under a single dosage regimen, subjects were administered either a single capsule containing controlled release propranolol equivalent to 160 mg of the drug or 80 mg of conventional propranolol tablet, twelve hourly. Peak plasma propranolol concentrations were low which occurred later after controlled release administration than after the administration of the conventional tablet. Analysis of the area under the plasma concentration-time curve (AUC) for the two formulations indicate no significant difference of bioavailability despite a prolonged absorption time and maintenance of effective plasma concentration for the controlled release preparation.     

Comparative investigations on the bioavailability of cefuroxime axetil.

In a three-way cross-over study the bioavailability of cefuroxime was determined in 12 healthy volunteers after oral administration of 250 mg as cefuroxime axetil (Elobact; CAS 64544-07-6) in a plain aqueous suspension and as tablets from different batches. The tablet formulations showed nearly identical pharmacokinetic parameters and were bioequivalent. The mean maximum serum concentration was 4.7 micrograms/ml, achieved after 2.1 h. The serum half-live was 1.2-1.4 h, the area under the serum concentration-time curve was 14.3-14.4 micrograms/ml.h and the urinary recovery of unchanged cefuroxime was 54%. The bioavailability of cefuroxime after administration of cefuroxime axetil in aqueous suspension was lower, but bio-inequivalence was not demonstrated.     

Comparison of two enteric-coated acetylsalicylic acid preparations by monitoring steady-state levels of salicylic acid and its metabolites in plasma and urine

In a randomized three-way crossover study, 12 healthy male volunteers were given multiple oral doses, i.e. 1.5 g b.i.d. for 7 days, of two different types of enteric-coated acetylsalicylic acid (ASA) preparations, one being a conventional enteric-coated tablet (ET) and the other enteric-coated granules (EG) in a capsule; conventional ASA tablets were used as a reference. Plasma levels and excretion of salicylic acid and some of its metabolites were investigated under steady-state conditions. Plasma salicylic acid (SA) and salicyluric acid (SUA) levels were determined using a liquid chromatographic method. Two separate analyses were done to quantitate the metabolites in urine. SA, SUA, and gentisic acid were each assayed by the method used for plasma. Total salicylate was also determined. There was no significant difference in urinary excretion of total salicylate between the three formulations. A diurnal variation in the excretion of SUA and SA in urine was found. The two enteric-coated formulations provided significantly higher morning plasma concentrations than the conventional aspirin. The AUC was found to be significantly higher for ET than for the other two formulations. EG gave more uniform plasma levels during the studied 12-h intervals and also less inter- and intra-individual variations than ET, indicating that a b.i.d. regimen may be suitable for EG.     

Bioavailability of acetylsalicylic acid and salicylic acid from rapid-and slow-release formulations,and in combination with dipyridamol

Summary Acetylsalicylic acid (ASA) is a strong, irreversible inhibitor of platelet aggregation, but loses this activity following first-pass deacetylation to salicylic acid (SA). In order to compare the bioavailability of unchanged ASA from rapid- and slow-release formulations, the single-dose concentration profiles of ASA and SA were studied in healthy volunteers following intake of two different rapid-release (conventional and effervescent tablets) and three different slow-release (microencapsulated ASA in tablets and in capsules, and enteric-coated tablets) formulations of ASA, and of one slow-release formulation of sodium salicylate. Since anti-platelet therapy with ASA is often combined with dipyridamol, the influence of this drug was also examined. The concentrations of ASA and SA were measured by high-pressure liquid chromatography. While the bioavailability of SA from the 5 ASA formulations was essentially equal and similar to that of the salicylate formulation, the bioavailability and peak concentrations of ASA appeared to be the much greater after rapid-release than after slow-release formulations. Indeed, ASA was only rarely detected in systemic blood following intake of slow-release ASA. Co-administered dipyridamol did not significantly influence the kinetics of ASA or SA. It appears that rapid-release formulations of ASA should be prefered in anti-platelet therapy, either alone or in combination with dipyridamol.