Colchicine is a supressor of hepatic CYP1A2 and theophylline is a sensitive CYP1A2 probe substrate. When the two are co-administered the potential exists for a clinically significant drug interaction. This study aims to determine the effect of steady-state colchicine on the pharmacokinetics of theophylline administered as a single dose. A secondary goal is to evaluate the safety and tolerability of this regimen in healthy volunteers. All study subjects will be monitored for adverse events throughout the entire study period.

Colchicine is a supressor of hepatic CYP1A2 and theophylline is a sensitive CYP1A2 probe substrate. When the two are co-administered the potential exists for a clinically significant drug interaction. This study aims to determine the effect of steady-state colchicine on the pharmacokinetics of theophylline administered as a single dose. After a fast of at least 10 hours, thirty healthy, non-smoking, non-obese, non-pregnant adult volunteers between the ages of 18 and 45 will be given one dose of 300mg (80mg/15ml concentrate) theophylline (theophylline elixir) on Day 1. Fasting will continue for 4 hours after the dose. Blood samples will be drawn from all participants before dosing and for 24 hours post-dose on a confined basis at times sufficient to adequately determine the pharmacokinetics of theophylline. Blood sampling will then continue on a non-confined basis on days 2-3. A four day washout period will be completed after the theophylline dose on Day 1 and prior to administration of the first colchicine dose on Day 5. Participants will return to the clinic on days 5-18 for non-confined dosing of colchicine (1x0.6mg twice daily every 12 hours). Administered dosing on these days will not necessarily be in a fasted state. Co-administration of a single 300mg dose of theophylline (80mg/15ml) and colchicine (1x0.6mg) will occur on the morning of Day 19 following a fast of at least 10 hours. Twelve hours later, subjects will receive the last dose of colchicine (1x0.6mg). Blood samples will be drawn from all participants before dosing on Day 19 and for 24 hours post-dose on a confined basis at times sufficient to adequately determine the pharmacokinetics of theophylline. Blood sampling will then continue on a non-confined basis on days 20 and 21. A further goal of this study is to evaluate the safety and tolerability of this regimen in healthy volunteers. Subjects will be monitored throughout participation in the study for adverse reactions to the study drug and/or procedures. Seated blood pressure and pulse will be measured prior to dosing and at approximately 1, 2, and 3 hours following drug administration on Days 1, 5 (after the morning dose) and 19. All adverse events whether elicited by query, spontaneously reported, or observed by clinic staff will be evaluated by the Investigator and reported in the subject's case report form.

Inclusion Criteria:

• Healthy adults 18-45 years of age, non smoking and non-pregnant (postmenopausal, surgically sterile or using effective contraceptive measures) with a body mass index (BMI) greater than or equal to 18 and less than or equal to 32, inclusive; hemoglobin greater than or equal to 11.5g/dL

Exclusion Criteria:

• Recent participation (within 28 days) in other research studies
• Recent significant blood donation or donation of plasma
• Pregnant or lactating
• Test positive at screening for human immunodeficiency virus (HIV), hepatitis B surface antigen (HbsAg), or hepatitis C virus (HCV)
• Recent (2-year) history or evidence of alcoholism or drug abuse
• Subjects who test positive for drugs of abuse or alcohol at screening or check-in
• History or presence of significant cardiovascular, pulmonary, hepatic, gallbladder or biliary tract, renal, hematological, gastrointestinal, endocrine, immunologic, dermatologic, neurological, or psychiatric disease or active sexually transmitted disease
• History of neuropathy or muscle disorders, peptic ulcer disease, clinically significant cardiac arrhythmias, seizure disorder, and low white blood cell count or other bone marrow disorders
• Subjects who have used any drugs or substances known to inhibit or induce cytochrome (CYP) P450 enzymes and/or P-glycoprotein (P-gp) within 28 days prior to the first dose and throughout the study
• History of allergy or sensitivity to colchicine or theophylline or aminophylline
• Subjects who have had a tattoo or body piercing within 30 days prior to administration of study drug
• Subjects with irritable bowel syndrome, chronic diarrhea or other chronic gastro-intestinal problems
• Subjects who are lactose intolerant

From the time of first study drug administration until 5 days after last dose.

At each visit the investigator had to document any occurrence of adverse events and abnormal laboratory findings. Any event spontaneously reported by the participant or observed by the investigator was recorded, irrespective of the relation to study treatment.