Antiplatelet effects of MK-852, a platelet fibrinogen receptor antagonist, in healthy volunteers

Platelet integrin αIIbβ3: signal transduction, regulation, and its therapeutic targeting

Integrins are a family of transmembrane glycoprotein signaling receptors that can transmit bioinformation bidirectionally across the plasma membrane. Integrin αIIbβ3 is expressed at a high level in platelets and their progenitors, where it plays a central role in platelet functions, hemostasis, and arterial thrombosis. Integrin αIIbβ3 also participates in cancer progression, such as tumor cell proliferation and metastasis. In resting platelets, integrin αIIbβ3 adopts an inactive conformation. Upon agonist stimulation, the transduction of inside-out signals leads integrin αIIbβ3 to switch from a low- to high-affinity state for fibrinogen and other ligands. Ligand binding causes integrin clustering and subsequently promotes outside-in signaling, which initiates and amplifies a range of cellular events to drive essential platelet functions such as spreading, aggregation, clot retraction, and thrombus consolidation. Regulation of the bidirectional signaling of integrin αIIbβ3 requires the involvement of numerous interacting proteins, which associate with the cytoplasmic tails of αIIbβ3 in particular. Integrin αIIbβ3 and its signaling pathways are considered promising targets for antithrombotic therapy. This review describes the bidirectional signal transduction of integrin αIIbβ3 in platelets, as well as the proteins responsible for its regulation and therapeutic agents that target integrin αIIbβ3 and its signaling pathways.

Safe prescribing of non-steroidal anti-inflammatory drugs in patients with osteoarthritis--an expert consensus addressing benefits as well as gastrointestinal and cardiovascular risks

BACKGROUND

There are several guidelines addressing the issues around the use of NSAIDs. However, none has specifically addressed the upper versus lower gastrointestinal (GI) risk of COX-2 selective and non-selective compounds nor the interaction at both the GI and cardiovascular (CV) level of either class of drugs with low-dose aspirin. This Consensus paper aims to develop statements and guidance devoted to these specific issues through a review of current evidence by a multidisciplinary group of experts.

METHODS

A modified Delphi consensus process was adopted to determine the level of agreement with each statement and to determine the level of agreement with the strength of evidence to be assigned to the statement.

RESULTS

For patients with both low GI and CV risks, any non-selective NSAID (ns-NSAID) alone may be acceptable. For those with low GI and high CV risk, naproxen may be preferred because of its potential lower CV risk compared with other ns-NSAIDs or COX-2 selective inhibitors, but celecoxib at the lowest approved dose (200 mg once daily) may be acceptable. In patients with high GI risk, if CV risk is low, a COX-2 selective inhibitor alone or ns-NSAID with a proton pump inhibitor appears to offer similar protection from upper GI events. However, only celecoxib will reduce mucosal harm throughout the entire GI tract. When both GI and CV risks are high, the optimal strategy is to avoid NSAID therapy, if at all possible.

CONCLUSIONS

Time is now ripe for offering patients with osteoarthritis the safest and most cost-effective therapeutic option, thus preventing serious adverse events which could have important quality of life and resource use implications. Please see related article: http://dx.doi.org/10.1186/s12916-015-0291-x.

How First-Time-in-Human Studies Are Being Performed: A Survey of Phase I Dose-Escalation Trials in Healthy Volunteers Published Between 1995 and 2004

First-time-in-human studies are small, time-lagged dose-escalation studies including volunteer subjects evaluating safety and tolerability. There is little consensus in the design of a first-time-in-human study, and it is difficult to get an overview of studies performed. One hundred five studies comprising 3323 healthy volunteers published in the 5 major clinical pharmacology journals since 1995 were analyzed. The average trial was placebo controlled, double blind including 32 subjects at 5 dose levels but with great variation in cohort size and dose-escalation method. The parallel single-dose design was the most common design, with the crossover designs being more frequent in the early publications. Despite discussions on the optimization of phase I trials, little seems to be happening. The development of study designs and evaluation methods for cancer trials is extensive, but formal statistically based methods and more scientific study designs are unusual in phase I dose-escalation trials in healthy volunteers.

Using pharmacokinetic principles to optimize pain therapy

Cyclo-oxygenase (COX) inhibitors are widely used to relieve musculoskeletal pain. These agents block the production of prostaglandins (PGs) at sites of inflammation by inhibiting the activity of two COX enzymes necessary for PG production and normal organ homeostasis. Inhibition of PG production at sites unrelated to pain is associated with adverse drug reactions (ADRs). The degree of analgesic efficacy, as well as the incidence and the localization of ADRs, are critically influenced by the pharmacokinetics (absorption, distribution and elimination) of these drugs. Ideally, sufficient and permanent inhibition of COX enzymes should be achieved in target tissues, with minimal ADRs. To minimize underdosing or overdosing, which result in therapeutic failure or ADRs, the COX inhibitor with the most appropriate pharmacokinetic properties should be selected on the basis of a thorough pharmacokinetic-pharmacodynamic analysis. In this Review, the pharmacokinetics of the prevailing COX inhibitors will be discussed and enigmatic aspects of these intensively used drugs will be considered.

Flavocoxid, an anti-inflammatory agent of botanical origin, does not affect coagulation or interact with anticoagulation therapies

INTRODUCTION

Flavocoxid, a botanical, anti-inflammatory agent, nonspecifically inhibits the peroxidase activity of cyclooxygenase (COX-1 and COX-2) enzymes and 5-lipooxygenase (5-LOX). Due to the concomitant use of aspirin or warfarin in many osteoarthritis (OA) patients with increased cardiovascular risk, we felt it necessary to assess the anticoagulation properties of flavocoxid.

METHODS

Three different studies were used: 1) a mouse model to assess effects on bleeding times when combined with aspirin; 2) the effect on platelet function as evaluated by platelet aggregation and bleed times in healthy human subjects; and 3) the effect on international normalized ratio in previously warfarinized patients with OA.

RESULTS

Flavocoxid at a human equivalent dose (HED) of 569 mg (within the standard human dosing range of 500 mg) produced no significant increases in bleeding time in mice. There was also no inhibition or synergistic increase in bleed times when flavocoxid was combined with aspirin (370 mg HED). Flavocoxid did not significantly inhibit thromboxane production or platelet aggregation, and did not increase bleeding times in healthy volunteers. Finally, flavocoxid did not inhibit or potentiate the anticoagulant effect of warfarin.

CONCLUSION

These results suggest that flavocoxid does not affect the primary or extrinsic pathways of secondary hemostasis and, by not inhibiting the anticoagulation effects of aspirin, may have utility in cardiovascular patients with OA.

Pooled analysis of thrombotic cardiovascular events in clinical trials of the COX-2 selective Inhibitor etoricoxib

BACKGROUND

A pooled analysis of randomized clinical trials data was performed to compare the rate of thrombotic cardiovascular events (thrombotic events) in patients taking the COX-2 selective inhibitor (coxib) etoricoxib, a traditional NSAID, or placebo.

METHODS

Data collected during all phase IIb/III etoricoxib clinical trials > or = 4 weeks in duration were evaluated. The pooled data set includes clinical information from approximately 6500 patient-years (PYs) of drug exposure in patients diagnosed with rheumatoid arthritis (RA), osteoarthritis (OA), ankylosing spondylitis (AS), or chronic low back pain (CLBP). Patients were treated with either etoricoxib (> or = 60 mg/day), the traditional NSAIDs naproxen (1000 mg/day), ibuprofen (2400 mg/day), diclofenac (150 mg/day), or placebo. The Relative risks (RRs) based on time to first occurrence of a thrombotic event in the etoricoxib group versus the comparator traditional NSAIDs or versus placebo were determined using patient-level data.

RESULTS

In the pooled dataset, a total of 74 thrombotic events occurred in 69 patients. The RRs for thrombotic events were 1.11 (95%CI: 0.32, 3.81) for etoricoxib (N = 2818) versus placebo (N = 1767); 0.83 (95%CI: 0.26, 2.64) for etoricoxib (N = 1266) versus the combined non-naproxen traditional NSAID group (ibuprofen and diclofenac; N = 718); and 1.70 (95%CI: 0.91, 3.18) for etoricoxib (N = 1960) versus naproxen (N = 1497).

CONCLUSIONS

There was no discernible difference in the incidence of thrombotic events in patients treated with etoricoxib versus non-naproxen traditional NSAIDs in this limited dataset. A trend toward more events with etoricoxib versus naproxen was observed. Despite the limited dataset available for this pooled analysis, these results are consistent with findings for other coxibs.

Cyclooxygenase-2 inhibition and coagulation

Selective inhibitors of cyclooxygenase-2 (COX-2) have come under scrutiny because of a possibly increased thrombotic risk observed in retrospective studies and comparatively small cancer trials. Indeed, inhibition of COX-2 may favor a prothrombotic environment by suppressing endothelial prostacyclin synthesis while leaving COX-1-dependent platelet thromboxane (TX) A2 synthesis unopposed. However, in vitro studies have shown that the effect of coxibs on coagulation is dependent on several variables; for example, the coxib celecoxib reduces endothelial tissue factor expression, a key initiator of the coagulation cascade. Furthermore, animal studies are inconclusive as some studies investigating the effect of COX-2 inhibition in atherosclerosis imply a detrimental effect of coxibs, whereas others suggest a beneficial effect on plaque progression and stability. In healthy human subjects and in patients with atherosclerotic vascular diseases, the effect of COX-2 inhibition on coagulation is equally unclear as no prospective, randomized, double-blinded studies sufficiently powered to investigate cardiovascular endpoints have been performed to directly investigate a potentially cardiotoxic effect of coxibs. Here, we review the effect of COX-2 inhibition on the coagulation system; we discuss the molecular mechanisms involved and summarize important clinical trials in which an increased frequency of thrombotic complications coxibs was observed.

Rizatriptan in the treatment of migraine

Migraine is a common, disabling disorder associated with considerable personal and societal burden. Current guidelines recommend triptans for the acute treatment of migraine unlikely to respond to less effective therapies. Rizatriptan is a second-generation triptan available in tablet or orally disintegrating tablet (wafer) formulations that offers several advantages over other members of its class. Rizatriptan is rapidly absorbed from the gastrointestinal tract and achieves maximum plasma concentrations more quickly than other triptans, providing rapid pain relief. Clinical trials have shown that rizatriptan is at least as effective or superior to other oral migraine-specific agents in the acute treatment of migraine, and has more consistent long-term efficacy across multiple migraine attacks. Rizatriptan has a favorable tolerability profile, and patients have reported greater satisfaction and a preference for rizatriptan over other migraine-specific agents. Improvements in quality of life reported with rizatriptan are consistent with its favorable efficacy and tolerability profiles. Notably, multi-attribute decision models that combine clinical data with patient- and physician-reported treatment preferences have identified rizatriptan as one of three triptans closest to a hypothetical "ideal". The efficacy and tolerability of rizatriptan for the acute treatment of migraine have thus been well established.

Preoperative administration of rofecoxib versus ketoprofen for pain relief after tonsillectomy

OBJECTIVES

We evaluated the analgesic efficacy and the opioid-sparing effect of oral rofecoxib compared with intramuscular (IM) ketoprofen in tonsillectomy.

METHODS

Seventy-seven adult patients were randomized into 2 groups: group R (n = 39), which received a single oral preoperative dose of rofecoxib 50 mg, and group K (n = 38), which received 2 IM doses of ketoprofen 100 mg (before surgery and after 12 hours). In both groups, additional IM meperidine hydrochloride 1 mg/kg was given. All patients received general anesthesia. A pain score (visual analog scale, 0 to 100) was assessed both at rest and during swallowing at 30 minutes and at 4, 8, 12, 16, and 24 hours after operation. If the pain score exceeded 40, patients were given meperidine as rescue analgesia.

RESULTS

The pain scores during rest and swallowing in group R were significantly lower (p < .05) than those of group K at 4, 8, and 12 hours after operation. Meperidine was given as rescue medication in significantly more patients of group K (76%) than of group R (38%; p < .05).

CONCLUSIONS

Oral premedication with rofecoxib seems to be more effective than use of ketoprofen in decreasing postoperative pain and the need for opioid rescue medication after elective tonsillectomy. Both drugs seem to be relatively safe as far as postoperative bleeding is concerned.

Presurgical intravenous parecoxib sodium and follow-up oral valdecoxib for pain management after laparoscopic cholecystectomy surgery reduces opioid requirements and opioid-related adverse effects

BACKGROUND

Opioids are associated with numerous adverse effects. It is unclear if reduced postoperative opioid consumption lowers the incidence and severity of opioid-related adverse effects. This analysis -- from a multicenter, randomized, double-blind trial -- tested if the reduction of opioid consumption among patients who received intravenous preoperative parecoxib 40 mg, followed by oral valdecoxib 40 mg qd postoperatively, in Days 1-4 after outpatient laparoscopic cholecystectomy surgery, reduced opioid-related symptoms.

METHODS

Patients received intravenous fentanyl for pain before discharge, and oral acetaminophen 500 mg hydrocodone 5 mg q 4-6 h prn postdischarge for up to 7 days postsurgery. Patients also received intravenous parecoxib 40 mg administered 30-45 min preoperatively, and valdecoxib 40 mg qd up to Day 4 and prn Days 5-7 postsurgery, or placebo. Patients completed an opioid-related Symptoms Distress Scale (SDS) questionnaire every 24 h for 7 days. Opioid use was converted to morphine-equivalent doses (MEDs). Clinically meaningful events (CMEs) for 12 opioid-related symptoms were assessed by three ordinal measures: frequency, severity, and bothersomeness. Reduction of CMEs on Day 1 and number of patient-days with CMEs on Days 1-4 were examined.

RESULTS

Cumulative MEDs on Day 0, Day 1, and Days 1-4 were significantly lower in the parecoxib/valdecoxib group compared with the placebo group (P < 0.001). At the end of Day 1, parecoxib/valdecoxib-treated patients had significantly lower SDS scores (P < 0.02), a significantly reduced incidence of CMEs (P < 0.05), and significantly fewer patient-days with CMEs in Days 1-4 than placebo patients (P < 0.05). Patients in the parecoxib/valdecoxib group were less likely to have CMEs for multiple symptoms than those in the placebo group (P < 0.001).

CONCLUSIONS

Treatment with parecoxib and valdecoxib significantly reduced the cumulative MED requirements, the incidence of opioid-related adverse effects, and patient-days with CMEs.

Acetylsalicylic Acid, Diclofenac, and Lornoxicam, but Not Rofecoxib, Affect Platelet CD 62 Expression

Nonsteroidal antiinflammatory drugs are routinely administered in the perioperative period. Because of the absence of cyclooxygenase-2 in platelets, cyclooxygenase-2-selective drugs are thought not to cause platelet inhibition. Because platelets play an important role in the coagulation process, the absence of platelet function inhibition may lead to fewer bleeding complications after surgery. We studied the influence of aspirin, diclofenac, lornoxicam, and rofecoxib on arachidonic acid and collagen-induced CD 62 P (P selectin) expression by using flow cytometry. Blood from 68 volunteers was obtained before and 1, 3, and 12 h after the oral ingestion of 1 of the randomly assigned study medications. Aspirin, diclofenac, and lornoxicam had a significant effect on arachidonic acid and collagen-induced CD 62 P expression in platelets, whereas rofecoxib did not show this effect. We conclude that rofecoxib is safe to use perioperatively with respect to inhibition of platelet function.

IMPLICATIONS

We compared the effect of rofecoxib and three nonselective nonsteroidal antiinflammatory drugs on platelet function, measured by CD 62 P expression. Platelet function was not altered by rofecoxib, but it was inhibited by aspirin, diclofenac, and lornoxicam. Rofecoxib may be safer than classic NSAIDs with respect to platelet function during the perioperative period.

Pharmacodynamic characterization of the interaction between the glycoprotein IIb/IIIa inhibitor YM337 and unfractionated heparin and aspirin in humans

AIMS

To investigate the pharmacodynamic interaction of unfractionated heparin (UFH) and acetylic salicylic acid (ASA) on YM337, a monoclonal humanized antibody of the platelet GPIIb/IIIa receptor.

METHODS

In a randomized, placebo-controlled study three treatment groups each with six healthy volunteers received the following medication: group 1, ASA (3 days) + UFH + YM337 (placebo); group 2, ASA (placebo) + UFH (placebo) + YM337; group 3, ASA + UFH + YM337. Assessments were made over 24 h and included bleeding time (BT), ADP (20 microm)- and collagen (5 microg ml-1)-induced platelet aggregation and PAC1 and CD62 expression measured by flow cytometry.

RESULTS

In group 3 BT was prolonged to 35 [median, 16-45 min (1,3 quartile)] after UFH administration, increasing to 45 [median, 42-45 min (1,3 quartile)] after YM infusion (6 h). BT remained elevated to 26 [median, 14-45 min (1,3 quartile)] at 24 h, while groups 1 and 2 returned to normal values. Collagen-induced aggregation was 73% [median, 70-80% (1,3 quartile)] under YM337 alone, 79% [median, 72-80% (1,3 quartile)] under ASA + UFH and reduced only in group 3 to 24% [median, 18-29% (1,3 quartile)]. In both groups receiving active YM337, PAC1 expression showed a reduction to < 20% after 6 h of infusion. CD62 expression was not significantly affected by any treatment.

CONCLUSION

UFH and YM337 have strong synergistic effects on BT, while coadministration of ASA strongly augments inhibitory effects of YM337 on collagen-induced platelet aggregation.

Aspirin in the prophylaxis of coronary artery disease

Aspirin has been used for more than 100 years, but its mechanisms of action have only been understood in the past 20 years. Aspirin interferes with arachidonic acid metabolism in platelets and endothelial cells and thereby reduces thromboxane A2 and prostacyclin. It also has other mechanisms of action, including anti-inflammatory roles, protection from oxidative stress, enhancement of fibrinolysis, and suppression of plasma coagulation and platelet-dependent inhibition of thrombin generation. It has been used for primary and secondary prevention of myocardial ischemia, and for primary and secondary prevention of cerebrovascular ischemia. We review the 5 pivotal studies relating to primary prevention for cardiovascular risk and the many studies relating to secondary prevention of myocardial ischemia. We also review the utility of aspirin in primary prevention of myocardial infarction and stroke. We conclude that aspirin is one of the most potent drugs ever discovered and that its effects extend well beyond those of cycloxoxygenase enzyme inhibition. Aspirin treatment does not preclude control of underlying and comorbid conditions such as diabetes mellitus, hypertension, and dyslipidemia. For most patients, a daily dose of 325 mg is optimal. Patients must understand the potential for gastrointestinal upset and hemorrhagic complications. The utility of aspirin is greater in coronary artery disease prevention than in cerebrovascular prevention.

Cyclooxygenase inhibitors and the antiplatelet effects of aspirin

BACKGROUND

Patients with arthritis and vascular disease may receive both low-dose aspirin and other nonsteroidal antiinflammatory drugs. We therefore investigated potential interactions between aspirin and commonly prescribed arthritis therapies

METHODS

We administered the following combinations of drugs for six days: aspirin (81 mg every morning) two hours before ibuprofen (400 mg every morning) and the same medications in the reverse order; aspirin two hours before acetaminophen (1000 mg every morning) and the same medications in the reverse order; aspirin two hours before the cyclooxygenase-2 inhibitor rofecoxib (25 mg every morning) and the same medications in the reverse order; enteric-coated aspirin two hours before ibuprofen (400 mg three times a day); and enteric-coated aspirin two hours before delayed-release diclofenac (75 mg twice daily)

RESULTS

Serum thromboxane B(2) levels (an index of cyclooxygenase-1 activity in platelets) and platelet aggregation were maximally inhibited 24 hours after the administration of aspirin on day 6 in the subjects who took aspirin before a single daily dose of any other drug, as well as in those who took rofecoxib or acetaminophen before taking aspirin. In contrast, inhibition of serum thromboxane B(2) formation and platelet aggregation by aspirin was blocked when a single daily dose of ibuprofen was given before aspirin, as well as when multiple daily doses of ibuprofen were given. The concomitant administration of rofecoxib, acetaminophen, or diclofenac did not affect the pharmacodynamics of aspirin

CONCLUSIONS

The concomitant administration of ibuprofen but not rofecoxib, acetaminophen, or diclofenac antagonizes the irreversible platelet inhibition induced by aspirin. Treatment with ibuprofen in patients with increased cardiovascular risk may limit the cardioprotective effects of aspirin.

A high level of cyclooxygenase-2 inhibitor selectivity is associated with a reduced interference of platelet cyclooxygenase-1 inactivation by aspirin

Both nonsteroidal anti-inflammatory drugs, such as ibuprofen, and the prototypical selective cyclooxygenase (Cox)-2 inhibitors DuP-697 and NS-398 block the inhibition of Cox-1 by aspirin in vitro. However, clinical studies have shown that the Cox-2 selective drugs (or coxibs) rofecoxib and etoricoxib, at therapeutic doses, do not interfere with the antiplatelet effect of aspirin, in contrast to ibuprofen. Here, we have evaluated the relative potential of ibuprofen and various coxibs to interfere with the inactivation of Cox-1 by aspirin by using purified enzyme and calcium ionophore-activated human platelets. The irreversible inactivation of Cox-1 by aspirin can be antagonized by ibuprofen and coxibs, albeit with widely different potencies. The rank order of potencies for this process (ibuprofen > celecoxib > valdecoxib > rofecoxib > etoricoxib) parallels that obtained for the inhibition of Cox-1-mediated thromboxane B(2) production by calcium ionophore-stimulated platelets. The antagonism of aspirin therefore likely involves a competition at the enzyme active site. The EC(50) value for the antagonism against 10 microM aspirin for each drug is approximately 10- to 40-fold lower than the corresponding IC(50) value for inhibition of platelet Cox-1 activity, consistent with the much weaker initial binding of aspirin to Cox-1 as compared with arachidonic acid. These results show that a low affinity for Cox-1 and a high degree of Cox-2 selectivity confers a low potential to block aspirin inhibition of platelet Cox-1, consistent with the results of clinical studies.

Rofecoxib: a review of its use in the management of osteoarthritis, acute pain and rheumatoid arthritis

Rofecoxib is a selective cyclo-oxygenase (COX)-2 inhibitor which has little or no effect on the COX-1 isoenzyme at doses up to 1000 mg/day. Rofecoxib has greater selectivity for COX-2 than celecoxib, meloxicam, diclofenac and indomethacin. In well-controlled clinical trials, rofecoxib 12.5 to 500 mg/day has been evaluated for its efficacy in the treatment of osteoarthritis, acute pain and rheumatoid arthritis [lower dosages (5 to 125 mg/day) were generally used in the chronic pain indications]. In the treatment of patients with osteoarthritis, rofecoxib was more effective in providing symptomatic relief than placebo, paracetamol (acetaminophen) and celecoxib and was similar in efficacy to ibuprofen, diclofenac, naproxen and nabumetone. Overall, both the physician's assessment of disease status and the patient's assessment of response to therapy tended to favour rofecoxib. In patients with postsurgical dental pain, pain after spinal fusion or orthopaedic surgery, or primary dysmenorrhoea, rofecoxib provided more rapid and more sustained pain relief and reduced requirements for supplemental morphine use after surgery than placebo. Rofecoxib was more efficacious than celecoxib in patients with acute dental pain and pain after spinal fusion surgery, although celecoxib may have been used at a subtherapeutic dose. In comparison with traditional nonsteroidal anti-inflammatory drugs (NSAIDs) ibuprofen, diclofenac and naproxen sodium, rofecoxib was similar in efficacy in the treatment of acute pain. Although naproxen sodium provided more rapid pain relief than rofecoxib in patients with primary dysmenorrhoea, the reverse was true after orthopaedic surgery: rofecoxib provided more rapid pain relief and less supplemental morphine was needed. Rofecoxib was as effective as naproxen in providing symptomatic relief for over 8700 patients with rheumatoid arthritis. Compared with traditional NSAID therapy, rofecoxib had a significantly lower incidence of endoscopically confirmed gastroduodenal ulceration and, in approximately 13,000 patients with osteoarthritis and rheumatoid arthritis, a lower incidence of gastrointestinal (GI) adverse events. Rofecoxib was generally well tolerated in all indications with an overall tolerability profile similar to traditional NSAIDs. The most common adverse events in rofecoxib recipients were nausea, dizziness and headache. In conclusion, rofecoxib is at least as effective as traditional NSAID therapy in providing pain relief for both chronic and acute pain conditions. Rofecoxib provides an alternative treatment option to traditional NSAID therapy in the management of symptomatic pain relief in patients with osteoarthritis. Initial data from patients with primary dysmenorrhoea and postoperative pain are promising and further trials may confirm its place in the treatment of these indications. Rofecoxib has also shown promising results in patients with rheumatoid arthritis and is likely to become a valuable addition to current drug therapy for this patient population. Importantly, rofecoxib is associated with a lower incidence of GI adverse events than traditional NSAIDs making it a primary treatment option in patients at risk of developing GI complications or patients with chronic conditions requiring long term treatment.