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Fosamax
is a bisphosphonate that acts as a specific inhibitor of osteoclast-mediated
bone resorption. Bisphosphonates are synthetic analogs of pyrophosphate
that bind to the hydroxyapatite found in bone. Bone-building treatment
using Fosamax has helped HIV-positive people to recover from osteoporosis.
Because of certain restrictions (see Patient Information) related to this
treatment, such as it must be taken in the morning with no food for half
an hour, some clinicians suggest calcitonin by nasal inhaler instead.
How
Supplied: 5, 10, 35, and 40 mg tablets, and a 70 mg once weekly tablet
Indications
for Use: Anti-osteoporosis, Anti-Paget’s Disease. Fosamax is for the
treatment or prevention of osteoporosis (thinning of bone) in women after
menopause. It reduces the chance of having a hip or spinal fracture. It
is also helpful to increase bone mass in men with osteoporosis. Fosamax
is used for the treatment of osteoporosis in both men and women receiving
corticosteroid medications (for example, prednisone).
Mechanism of Action:
At the cellular level, alendronate shows preferential localization to sites
of bone resorption, specifically under osteoclasts. Fosamax reduces the
activity of the cells that cause bone loss and decreases the rate of bone
loss that occurs after menopause or with corticosteroid medications.
Pharmacokinetics:
Absorption: Bioavailability was decreased (by approximately 40%) when
10 mg alendronate was administered either ½ to 1 hour before a standardized
breakfast, when compared to dosing 2 hours before eating. In studies of
treatment and prevention of osteoporosis, alendronate was effective when
administered at least 30 minutes before breakfast.
Distribution:
Pre-clinical studies show that alendronate transiently distributes to soft
tissues following 1 mg/kg IV administration but is then rapidly redistributed
to bone or excreted in the urine.
Metabolism: There
is no evidence that alendronate is metabolized in animals or humans.
Excretion:
Plasma concentrations fell by more than 95% within 6 hours following IV
administration.
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