Celecoxib

Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, is a nonsteroidal anti-inflammatory drug (NSAID) which is known for its decreased risk of causing gastrointestinal bleeding compared to other NSAIDS. It is used to manage symptoms of various types of arthritis pain and in familial adenomatous polyposis (FAP) to reduce precancerous polyps in the colon.

Interestingly, selective COX-2 inhibitors (especially celecoxib), have been evaluated as potential cancer chemopreventive and therapeutic drugs in clinical trials for a variety of malignancies.

Celecoxib is an NSAID used to treat osteoarthritis, rheumatoid arthritis, acute pain, menstrual symptoms, and to reduce polyps is familial adenomatous polyposis.

Celecoxib is indicated for symptomatic treatment of adult osteoarthritis (OA) and adult rheumatoid arthritis (RA). Celecoxib is not a substitute for aspirin for cardiovascular event prophylaxis.

It may be also be used to treat acute pain from various sources, juvenile rheumatoid arthritis in children over 2, ankylosing spondylitis, and primary dysmenorrhea.

• Ankylosing Spondylitis (AS)
• Osteoarthritis (OA)
• Pain
• Acute
• Primary Dysmenorrhoea
• Rheumatoid Arthritis
• Rheumatoid Arthritis
• Juvenile

Celecoxib inhibits cyclooxygenase 2 (COX-2) enzyme, reducing pain and inflammation. It is important to note that though the risk of bleeding with celecoxib is lower than with certain other NSAIDS, it exists nonetheless and caution must be observed when it is administered to those with a high risk of gastrointestinal bleeding.

A note on the risk of cardiovascular events

Significant concerns regarding the safety of COX-2 selective NSAIDs emerged in the early 2000s. Rofecoxib, another member of the COX-2 inhibitor drug class, also known as Vioxx, was withdrawn from the market due to prothrombotic cardiovascular risks. Following an FDA Advisory Committee meeting in 2005, in which data from large clinical outcome trials were evaluated, the FDA concluded that the risk for cardiovascular thrombotic events for both COX-2 selective NSAIDs and nonselective NSAIDs was evident. It was determined that the benefits of celecoxib treatment, however, outweighed the risks. Postmarketing cardiovascular outcomes trial (PRECISION) revealed that the lowest possible dose of celecoxib was similar in cardiovascular safety to moderate strength doses of both naproxen and ibuprofen. Patients who had previous cardiovascular events including acute MI, coronary revascularization, or coronary stent insertion were not evaluated in the trial. It is not advisable to administer NSAIDS to these groups of patients.

Unlike most NSAIDs, which inhibit both types of cyclooxygenases (COX-1 and COX-2), celecoxib is a selective noncompetitive inhibitor of cyclooxygenase-2 (COX-2) enzyme. COX-2 is expressed heavily in inflamed tissues where it is induced by inflammatory mediators. The inhibition of this enzyme reduces the synthesis of metabolites that include prostaglandin E2 (PGE2), prostacyclin (PGI2), thromboxane (TXA2), prostaglandin D2 (PGD2), and prostaglandin F2 (PGF2). Resultant inhibition of these mediators leads to the alleviation of pain and inflammation.

By inhibiting prostaglandin synthesis, non-steroidal anti-inflammatory drugs (NSAIDs) cause mucosal damage, ulceration and ulcer complication throughout the gastrointestinal tract. Celecoxib poses less of an ulceration risk than other NSAIDS, owing to its decreased effect on gastric mucosal prostaglandin synthesis when compared to placebo.

Celecoxib exerts anticancer effects by binding to the cadherin-11 (CDH11)protein, which is thought to be involved in the progression of tumors, and inhibiting the 3-phosphoinositide-dependent kinase-1 (PDK-1) signaling mechanism. In addition, celecoxib has been found to inhibit carbonic anhydrase enzymes 2 and 3, further enhancing its anticancer effects.

As mentioned in the pharmacodynamics section of this drug entry, celecoxib may cause an increased risk of thrombotic events. The risk of thrombosis resulting from COX-2 inhibition is caused by the vasoconstricting actions of thromboxane A2, leading to enhanced platelet aggregation, which is uncontrolled when the actions of prostacyclin, a platelet aggregation inhibitor, are suppressed through the inhibition of COX-2.

Celecoxib is absorbed rapidly in the gastrointestinal tract. When a single oral dose of 200 mg was given to healthy research subjects, the peak plasma levels of celecoxib occurred within 3 hours. The Cmax is 705 ng/mL. When multiple doses are given, steady-state concentrations are reached on or before day 5. When taken with a high-fat meal, peak plasma levels are delayed for about 1 to 2 hours with an increase in total absorption (AUC) of 10% to 20%. The AUC of celecoxib has been shown to be significantly lower in patients with chronic renal impairment. A meta-analysis of pharmacokinetic studies has suggested an approximately 40% higher AUC (area under the curve) of celecoxib in black patients compared to Caucasians for unknown reasons.

The apparent volume of distribution of celecoxib at steady state (Vss/F) is about 429 L, which suggests wide distribution into various tissues. Celecoxib is not preferentially bound to red blood cells. Another resource reports a volume of distribution of 455 ± 166L.

The protein binding of celecoxib is 97%, and it is primarily bound to albumin.

Celecoxib is primarily eliminated by hepatic metabolism with small amounts (12 About 57% of an oral dose of celecoxib is excreted in the feces and 27% is found to be excreted into the urine in the form of metabolites. The main metabolite in urine and feces is identified as the carboxylic acid metabolite (73%). The amount of glucuronide in the urine is reported to be low.

The effective half-life of celecoxib is approximately 11 hours when a single 200 mg dose is given to healthy subjects. The terminal half-life of celecoxib varies because of its low solubility, which prolongs absorption.

Apparent clearance (CL/F), single oral 200 mg dose, healthy subjects = 27.7 L/hr. Clearance may be decreased by about 47% in patients with chronic renal insufficiency, according to a pharmacokinetic study. Studies have not been performed in patients with severe renal impairment.

The oral TDLo in humans 5.71 mg/kg.

It is not advisable to administer celecoxib in patients with renal impairment or advanced hepatic impairment, as this may lead to increased serum concentrations, causing toxicity. Symptoms of overdose may include breathing difficulties, coma, drowsiness, gastrointestinal bleeding, high blood pressure, kidney failure, nausea, sluggishness, stomach pain, and vomiting. Because serious gastrointestinal tract ulceration and bleeding can occur without preceding symptoms, patients should be monitored for signs/symptoms of gastrointestinal bleeding. Symptomatic and supportive measures should be taken in a celecoxib overdose. The induction of emesis or administration of active charcoal should take place if the patient is seen within 4 hours of celecoxib ingestion. Diuresis, urinary alkalinization, hemodialysis, or hemoperfusion may not be useful in a celecoxib overdose due to its high level of protein binding.

• Avoid alcohol. Alcohol increases the risk of gastrointestinal irritation.
• Avoid multivalent ions. Separate the administration of aluminum and magnesium containing drugs by several hours.
• Take with or without food. Doses up to 200 mg can be taken without regard to food, but doses of 400mg or higher should be taken with food.