From peptic ulcer disease to NSAID gastropathy. An evolving nosology

Understanding the selectivity of nonsteroidal anti-inflammatory drugs for cyclooxygenases using quantum crystallography and electrostatic interaction energy

Quantum crystallography methods have been employed to investigate complex formation between nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase (COX) enzymes, with particular focus on the COX-1 and COX-2 isoforms. This study analyzed the electrostatic interaction energies of selected NSAIDs (flurbiprofen, ibuprofen, meloxicam and celecoxib) with the active sites of COX-1 and COX-2, revealing significant differences in binding profiles. Flurbiprofen exhibited the strongest interactions with both COX-1 and COX-2, indicating its potent binding affinity. Celecoxib and meloxicam showed a preference for COX-2, consistent with their known selectivity for this isoform, while ibuprofen showed comparable interaction energies with both isoforms, reflecting its nonselective inhibition pattern. Key amino-acid residues, including Arg120, Arg/His513 and Tyr355, were identified as critical determinants of NSAID selectivity and binding affinity. The findings highlight the complex interplay between interaction energy and selectivity, suggesting that while electrostatic interactions play a fundamental role, additional factors such as enzyme dynamics and the hydrophobic effect also contribute to the therapeutic efficacy and safety profiles of NSAIDs. These insights provide valuable guidance for the rational design of NSAIDs with enhanced therapeutic benefits and minimized adverse effects.

Increased susceptibility of ethanol-treated gastric mucosa to naproxen and its inhibition by DA-9601, an Artemisia asiatica extract

AIM

To examine the effect of DA-9601, a new gastroprotective agent, on the vulnerability of ethanol-treated rat's stomach to naproxen (NAP).

METHODS

Male Sprague-Dawley rats were pretreated with 1 mL of 50% ethanol twice a day for 5 d and then NAP (50 mg/kg) was administered. DA-9601 was administered 1 h before NAP. Four hours after NAP, the rats were killed to examine gross injury index (mm2), histologic change and to determine mucosal levels of malondialdehyde (MDA), prostaglandin E2 (PGE2), glutathione (GSH) and myeloperoxidase (MPO).

RESULTS

Pretreatment of ethanol significantly increased NAP-induced gastric lesions, as well as an increase in MDA and MPO. On the contrary, mucosal PGE2 and GSH contents were decreased dramatically by ethanol pretreatment, which were aggravated by NAP. DA-9601 significantly reduced NAP-induced gastric injury grossly and microscopically, regardless of pretreatment with ethanol. DA-9601 preserved, or rather, increased mucosal PGE2 and GSH in NAP-treated rats (P<0.05), with reduction in mucosal MDA and MPO levels.

CONCLUSION

These results suggest that repeated alcohol consumption renders gastric mucosa more susceptible to NSAIDs though, at least in part, reduction of endogenous cytoprotectants including PGE2 and GSH, and increase in MPO activation, and that DA-9601, a new gastroprotectant, can reduce the increased vulnerability of ethanol consumers to NSAIDs-induced gastric damage via the mechanism in which PGE2 and GSH are involved.

A comparison of the upper gastrointestinal mucosal effects of valdecoxib, naproxen and placebo in healthy elderly subjects

BACKGROUND

In long-term outcomes studies, cyclooxygenase COX-2 specific inhibitors spare COX-1 at supratherapeutic doses and therefore demonstrate improved gastrointestinal safety over nonspecific nonsteroidal anti-inflammatory drugs (NSAIDs). However, in clinical practice, anti-inflammatory drugs are often used for short-term treatment of pain.

AIM

To compare the short-term upper gastrointestinal mucosal effects of naproxen with the new COX-2 specific inhibitor, valdecoxib, or placebo, in elderly subjects.

METHODS

In this multicentre, double-blind, randomized, study, elderly subjects (65-76 years old), with a normal baseline esophagogastroduodenoscopy (EGD), received oral valdecoxib (a supratherapeutic 40 mg b.d. dosage, n = 62), naproxen (500 mg b.d., n = 62), or placebo (n = 62) for 6.5 days. Upper gastrointestinal mucosal injury was evaluated post-treatment by EGD (day 7).

RESULTS

Subjects receiving naproxen (11/60, 18%) had significantly more gastroduodenal ulcers post-treatment than those receiving placebo (2/61, 3%; P < 0.01) or valdecoxib (0/60, 0%; P < 0.001). A similar significant finding was observed for gastric ulcer rates. All treatments had similar adverse event rates and clinical laboratory findings.

CONCLUSIONS

Valdecoxib, even at supratherapeutic doses, was associated with an ulcer rate significantly lower than naproxen but similar to placebo in healthy elderly subjects, despite the short duration of therapy (6.5 days). Naproxen and valdecoxib were as well tolerated as placebo.

Aged gastric mucosa: Mechanisms of vulnerability

The incidence, frequency of complications and mortality of gastric ulcer disease are increased four-fold in the elderly taking non-steroidal anti-inflammatory drugs (NSAID). There is controversy as to whether this reflects increased usage of NSAID or specific vulnerability associated with age. We have investigated two possible mechanisms for this increase in gastrointestinal effects in the elderly: (i) increased susceptibility to acute gastrotoxicity; and (ii) reduced adaptation to NSAID, in a model of young (2 month), mature (12 month) and aged (24 month) rats. Aspirin damaged 7.7% of the volume of gastric mucosa in the young rat. In mature and aged rats, this increased to 11.3% (P < 0.002 compared to control) and 21.9% (P < 0.005 compared to control), respectively. Thus, aspirin caused a three-fold increase in the severity of acute gastric mucosal injury in aged animals. However, indomethacin, ibuprofen and L745 337 did not produce any significant acute gastric mucosal damage in 2-, 12- or 24-month-old rats. Significant gastric adaptation to diclofenac treatment occurred in both aged and young rats as measured by gastric mucosal damage. The aged gastric mucosa adapted equally as well as the young gastric mucosa to diclofenac. The findings of this study provide only modest support to the hypothesis of increased vulnerability of the stomach in the aged. Aspirin was associated with greater damage in the aged. Adaptation to diclofenac-induced damage was not reduced in the aged and there was not an increased susceptibility to damage by the non-aspirin NSAID tested. The selective cyclo-oxygenase-2 inhibitor, L745 337, was the least toxic agent and may represent a group of NSAID which cause fewer gastrointestinal complications in the elderly.

Improving drug use in rheumatic disorders

A recent study concluded that approximately 50 elderly people are admitted to the major teaching hospital in Tasmania, Australia each year suffering from gastrointestinal bleeding related to the use of nonsteroidal anti-inflammatory drugs (NSAIDs). The aim of this study was to examine whether academic detailing, designed to encourage a rational approach to the prescribing of NSAIDs and performed by a pharmacist; could modify prescribing practices in the community. The intervention was conducted in Southern Tasmania, using the north of the state as a control area. The target group of all general practitioners (approximately 250) working in Southern Tasmania was sent educational material designed to assist in the appropriate prescribing of NSAIDs. A pharmacist then visited each general practitioner and discussed the rational use of NSAIDs directly with them. The outcome of the programme was measured using evaluation feedback from the general practitioners and pharmacoepidemiological data provided by (i) a state-wide pharmacoepidemiology database derived from community pharmacy records, and (ii) dispensing under the Pharmaceutical Benefits and Repatriation Pharmaceutical Benefits Schemes. The key variable examined was the defined daily dose (DDD) dispensed for the NSAIDs compared with paracetamol. The educational programme was very well received by the general practitioners. Changes in the prescribing of NSAIDs were evident in both study regions, but were more marked in the intervention area. For instance, the state-wide pharmacoepidemiological database indicated that the ratio of dispensed DDDs of NSAIDs: paracetamol declined from 3.00 to 2.59 in the intervention region and remained steadier (3.16 to 2.92) in the north of the state. The improvement was significantly greater in the intervention region. This study has revealed that an educational programme utilizing academic detailing by pharmacists can modify prescribing practices within the community setting.

Effects of nabumetone on platelet function in healthy volunteers

Non-steroidal anti-inflammatory drugs (NSAID) are frequently prescribed but gastrointestinal haemorrhages and inhibition of platelet function are two side effects that limit their use. Nabumetone belongs to a new prostaglandin-sparing class of NSAID with a low potential for causing gastrointestinal mucosal irritancy and inhibition of platelet function. We have used flow cytometry and in vitro bleeding time (IVBT) to measure the effects of nabumetone on platelet function in healthy volunteers. Nabumetone was found to cause a significant decrease in platelet-bound fibrinogen after adenosine diphosphate (ADP) activation using flow cytometry and a significant increase in IVBT when using CaCl(2) as activating substance. The platelet inhibitory effect was less pronounced than the changes seen with low dose aspirin. Flow cytometry and IVBT are two sensitive methods well suited for clinical use and could both be used to monitor drug-induced inhibition of platelet function.