The pKa (the pH at which 50% of the drug becomes positively charged) of rabeprazole is around 5.0, meaning that it doesnt take a lot of acid to activate it. While this theoretically translates into a faster onset of action for rabeprazoles acid-inhibiting effect, the clinical implications of this fact have yet to be elucidated. Pharmacokinetics
Rabeprazoles bioavailability is approximately 52%, meaning that 52% of orally administered dose is expected to enter systemic circulation (the bloodstream). Once in the blood, rabeprazole is approximately 96.3%-97% bound to plasma proteins. The biological half-life of rabeprazole in humans is approximately one hour. It takes about 3.5 hours for rabeprazole to reach the maximum concentration in human plasma after a single orally administered dose. Oral absorption is independent of the dose administered.Rabeprazole is extensively metabolized by the liver. 90% of the drug is rendered into metabolites by the liver, which are then excreted by the kidneys. 10% of the dose is excreted in the feces. The drug metabolizing enzymes primarily responsible for rabeprazoles metabolism are CYP2C19 and CYP3A4. However, rabeprazole is mainly metabolized through non-enzymatic reduction to a thioether metabolite. Some of rabeprazoles metabolites include the following: a thioether carboxylic acid metabolite, a thioether glucuronide metabolite, and a sulfone metabolite. The most common metabolites excreted in the urine are the mercapturic acid conjugate and carboxylic acid. A diagram of rabeprazoles phase I metabolism is shown below. Pharmacogenetics
The effect of rabeprazole may vary based upon the genetics of the individual taking the medication.
Radicular pain, or radiculitis, is pain "radiated" along the dermatome (sensory distribution) of a nerve due to inflammation or other irritation of the nerve root (radiculopathy) at its connection to the spinal column. A common form of radiculitis is sciatica – radicular pain that radiates along the sciatic nerve from the lower spine to the lower back, gluteal muscles, back of the upper thigh, calf, and foot as often secondary to nerve root irritation from a spinal disc herniation or from osteophytes in the lumbar region of the spine. Radiculitis indicates inflammation of the spinal nerve root, which may lead to pain in that nerves distribution without weakness as opposed to radiculopathy. When the radiating pain is associated with numbness or weakness, the diagnosis is radiculopathy if the lesion is at the nerve root and myelopathy if at the spinal cord itself. See also
Intervertebral disc
Sciatica
Spinal disc herniation

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