Innovations in topical therapy

Topical delivery of therapeutic agents in the treatment of inflammatory bowel disease

For targeting local and systemic inflammatory processes in inflammatory bowel disease (IBD) therapeutic agents of first choice (e.g. aminosalicylates, corticosteroids) have been developed in special galenic forms to accomplish the topical delivery of the active compounds to the terminal ileum (Crohn's disease) and/or the colon (Crohn's disease and ulcerative colitis). However, it has to be realized that intestinal physiology (e.g. motility, intraluminal pH profiles), extent and pattern of IBD as well as drug disposition demonstrate large interindividual differences resulting in variable clinical response rates between about 35% and 75%. 5-Aminosalicylate (5-AS) can be delivered to the colon either by azo-prodrugs (e.g. sulfasalazine, olsalazine or balsalazide) or by direct rectal administration of 5-AS in form of enemas, foam or suppositories. Such formulations will be only effective in patients with ulcerative colitis (UC). Various slow/controlled release preparations of 5-AS have been developed for oral use. Some of them (e.g. Pentasa, Salofalk) release sufficient 5-AS already in the small bowel which could provide some additional benefit in Crohn's disease (CD). As urinary and faecal recoveries of total 5-AS are similar for all oral formulations, no major clinical differences can be expected. Extent of the disease, profile of adverse effects and patient's acceptance provide some guidance for selection of the particular agent. Rectal installation of several glucocorticosteroids has been employed for many years. More recently scientific and clinical interest has been focused on budesonide which is extensively presystemically metabolized in the intestinal wall and the liver. Therefore, its systemic availability is low (10-15%) independent whether budesonide is administered orally as controlled release formulation in patients with CD or rectally as enema in patients with UC. Numerous pharmacokinetic and clinical studies have documented the anticipated topical delivery and clinical efficacy of this corticosteroid without serious side effects such as cushingoid features. It can be assumed that for any novel therapeutic principle in IBD the approach of topical delivery will be also tried.

Beneficial effect of trimebutine and N-monodesmethyl trimebutine on trinitrobenzene sulfonic acid-induced colitis in rats

The use of local anesthetics, such as lidocaine, has been proposed in the treatment of distal ulcerative colitis. Trimebutine maleate (TMB) displays a local anesthetic activity higher than that of lidocaine in rabbit corneal reflex. TMB and nor-TMB its main metabolite in human show similar affinity to that of bupivacaine toward sodium channel labeled by [3H]batrachotoxin and block sodium currents in sensory neurons from rat dorsal root ganglia. The aim of this study was to evaluate the effects of TMB and nor-TMB in comparison to lidocaine and bupivacaine in a rat model of acute colonic inflammation induced by trinitrobenzene sulfonic acid (TNBS). A single intracolonic instillation of TNBS (50 mg/kg dissolved in ethanol 30%) led to early plasma extravasation then macroscopic damage (hyperemia and necrosis), increased colonic weight and tissular MPO, a marker of neutrophilic infiltration. Local administration of TMB at dose of 3 to 60 mg/kg, 30 min before, 24 and 48 h after colitis induction, significantly reduced the severity of colitis. Nor-TMB (1, 3, 10, 30 mg/kg) as well as lidocaine (1, 3, 10 mg/kg) dose-dependently reduced colitis while bupivacaine at 10 mg/kg did not affect it significantly. In contrast systemic administration of TMB, nor-TMB and lidocaine at 10 mg/kg had no significant effect. Furthermore, local administration of TMB (30 mg/kg) and lidocaine (10 mg/kg) significantly reduced plasmatic extravasation. In conclusion, intracolonic treatment with TMB and nor-TMB improved acute experimental TNBS-induced colitis in rat and these effects could be explained by their local anesthetic activity.

Treatment of inflammatory bowel disease with corticosteroids

Corticosteroids are a mainstay in the treatment of inflammatory bowel disease. Administered topically, orally, or intravenously corticosteroids rapidly and consistently improve moderate to severe active ulcerative colitis and Crohn's disease, although they are ineffective in the maintenance of remission in either illness. The beneficial effects of corticosteroid therapy are counterbalanced by their many side effects. A better understanding of the mechanism of steroid action and toxicity has led to the development of novel corticosteroids that offer the promise of continued efficacy with minimal toxicity. This article reviews the role of conventional and novel corticosteroids in the management of inflammatory bowel disease.

Review article: Immunosuppressants in distal ulcerative colitis

BACKGROUND

Distal ulcerative colitis may prove to be resistant to steroids and aminosalicylates, but total colectomy is more difficult to justify than in severe extensive colitis. Immunosuppression is of established benefit in generalized colitis, but there are no data available specific to distal disease.

AIM

To determine whether the protocol-driven use of immunosuppressants in resistant distal ulcerative colitis is of similar efficacy and safety to that in extensive disease.

METHODS

Two hundred and twenty-eight patients with distal ulcerative colitis seen in a 5-year period were identified from a prospective database. Details of 52 who had received immunosuppression were analysed.

RESULTS

The 52 patients received 68 courses of therapy (53 azathioprine, five mercaptopurine, 10 ciclosporin). The thiopurines yielded clinically valuable responses in only 43% of courses, with failure of response in 16% and toxicity in 34%. Ciclosporin was helpful on only two of 10 occasions. Eight patients required total colectomy. Adverse events were typical of those normally associated with immunosuppressants, with potential risk to life in seven patients; treatment was discontinued because of toxicity on a total of 31% of occasions.

CONCLUSIONS

Immunosuppression appears to be of lower efficacy and higher toxicity in resistant distal colitis than when used in more extensive colitis.