Overview
11 DESCRIPTION Colchicine is an alkaloid chemically described as (S)N-(5,6,7,9-tetrahydro-1,2,3,10-tetramethoxy-9-oxobenzo [alpha] heptalen-7-yl) acetamide with a molecular formula of C 22 H 25 NO 6 and a molecular weight of 399.4. The structural formula of colchicine is given below.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action The mechanism by which colchicine tablets exert its beneficial effect in patients with FMF has not been fully elucidated; however, evidence suggests that colchicine may interfere with the intracellular assembly of the inflammasome complex present in neutrophils and monocytes that mediates activation of interleukin-1β. Additionally, colchicine disrupts cytoskeletal functions through inhibition of β-tubulin polymerization into microtubules and consequently prevents the activation, degranulation and migration of neutrophils thought to mediate some gout symptoms. 12.3 Pharmacokinetics Absorption In healthy adults, colchicine tablets are absorbed when given orally, reaching a mean C max of 2.5 ng/mL (range 1.1 to 4.
Indications
- 1 INDICATIONS AND USAGE Colchicine tablets are an alkaloid indicated for: • Prophylaxis and treatment of gout flares in adults ( 1.1 ). • Familial Mediterranean fever (FMF) in adults and children 4 years or older ( Error! Hyperlink reference not valid. ). 1.1 Gout Flares Colchicine tablets are indicated for prophylaxis and the treatment of acute gout flares. • Prophylaxis of Gout Flares: Colchicine tablets are indicated for prophylaxis of gout flares. • Treatment of Gout Flares: Colchicine tablets are indicated for treatment of acute gout flares when taken at the first sign of a flare. 1.
Common Doses
- 0.6 mg
- 1.2 mg
- 2.4 mg
- 1.8 mg
Dosage
2 DOSAGE AND ADMINISTRATION The long-term use of colchicine is established for FMF and the prophylaxis of gout flares, but the safety and efficacy of repeat treatment for gout flares has not been evaluated. The dosing regimens for colchicine tablets are different for each indication and must be individualized. The recommended dosage of colchicine tablets depends on the patient’s age, renal function, hepatic function and use of coadministered drugs [see Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. ] .
Contraindications
- 4 CONTRAINDICATIONS Patients with renal or hepatic impairment should not be given colchicine tablets in conjunction with P-gp or strong CYP3A4 inhibitors (this includes all protease inhibitors except fosamprenavir). In these patients, life-threatening and fatal colchicine toxicity has been reported with colchicine taken in therapeutic doses. Patients with renal or hepatic impairment should not be given colchicine tablets in conjunction with P-gp or strong CYP3A4 inhibitors ( Error! Hyperlink reference not valid. ).
Side Effects
- 6 ADVERSE REACTIONS Prophylaxis of Gout Flares: The most commonly reported adverse reaction in clinical trials of colchicine for the prophylaxis of gout was diarrhea. Treatment of Gout Flares: The most common adverse reactions reported in the clinical trial with colchicine tablets for treatment of gout flares were diarrhea (23%) and pharyngolaryngeal pain (3%). FMF: Gastrointestinal tract adverse effects are the most frequent side effects in patients initiating colchicine tablets, usually presenting within 24 hours, and occurring in up to 20% of patients given therapeutic doses.
Interactions
- 7 DRUG INTERACTIONS Colchicine is a substrate of the efflux transporter P-glycoprotein (P-gp). Of the cytochrome P450 enzymes tested, CYP3A4 was mainly involved in the metabolism of colchicine. If colchicine tablets are administered with drugs that inhibit P-gp, most of which also inhibit CYP3A4, increased concentrations of colchicine are likely. Fatal drug interactions have been reported. Physicians should ensure that patients are suitable candidates for treatment with colchicine tablets and remain alert for signs and symptoms of toxicities related to increased colchicine exposure as a...