Evaluation of the Pharmacokinetics of Metronidazole 10% Ointment Applied Peri Anally in Healthy Volunteers and Patients With Perianal Crohn's Disease

Inclusion Criteria: Patient group: * Male and female patients with Crohn's disease (diagnosed by radiology, endoscopy and pathology), with anorectal involvement. * Aged 18-65 years. * Have had perianal symptoms for longer than 2 months * Have a score of 5 or above in the Perianal Crohn's Disease Activity Index (PCDAI) * Have a score of 1 or above on the 'Type of perianal disease' assessment of the PCDAI * Subjects can be on concomitant medication. Acceptable regimens are: * Aminosalicylates at a dosage that has been stable for more than 4 weeks before screening;Infliximab on a stable infusion regimen; * Oral corticosteroids \<40mg per day; Methotrexate, provided that dosage has been stable for more than 4 weeks; azathioprine or mercaptopurine at a dosage that has been stable for more than 8 weeks; * Antibiotics at a dosage that has been stable for 4 weeks but excluding metronidazole. * Cyclosporin on a stable dose for more than 4 weeks. * If patients have setons these must have been in place for at least 4 weeks prior to screening. * If female, the subject must not be lactating and must be (a) post-menopausal, (b) surgically sterilised, or (c) have a negative pregnancy test result prior to entry into the study and will use double-barrier methods of contraception (two separate methods of birth control, one of which may include oral contraception) for the duration of the study. * Must have provided written informed consent to participate. Healthy volunteer group: * They have had surgery to the anus or rectum in the past 4 weeks. * Have a history of inflammatory bowel disease. * Allergic to metronidazole. * Are taking any prohibited medication. * Not prepared to refrain from drinking alcohol during the course of the study. * Deemed mentally incompetent. * Considered by their physician unlikely to be able to comply with the protocol. * Has donated blood within the past 3 months. * Taken part in an experimental drug study in the preceding three months. Exclusion Criteria: Patient group: * They have had surgery to the anus or rectum in the past 4 weeks. * They have a perianal abscess requiring incision and drainage. * They have a stoma of less than 6 months duration. * Allergic to metronidazole. * Are taking any prohibited medication. * Not prepared to refrain from drinking alcohol during the course of the study. * Deemed mentally incompetent. * Considered by their physician unlikely to be able to comply with the protocol. * Has donated blood within the past 3 months. * Taken part in an experimental drug study in the preceding three months. * Has donated blood within the past 3 months. * Taken part in an experimental drug study in the preceding three months. Healthy volunteer group: * They have had surgery to the anus or rectum in the past 4 weeks. * Have a history of inflammatory bowel disease. * Allergic to metronidazole. * Are taking any prohibited medication. * Not prepared to refrain from drinking alcohol during the course of the study. * Deemed mentally incompetent. * Considered by their physician unlikely to be able to comply with the protocol. * Has donated blood within the past 3 months. * Taken part in an experimental drug study in the preceding three months.