BISHOSPHONATES
BRAND NAME:- NOT AVAILABLE.
BISPHOSPHONATES (BPNs) are analogue of pyrophosphate: carbon atom replacing oxygen in the P-O-P skeleton. They inhibits bone resorption and have recently attracted considerable attention because of their ability to prevent osteoporosis in addition to their usefulness in metabolic bone disease and hypercalcaemia. They are the most effective antiresorptive drugs . Chronologically and according to potency, the BPNs can be grouped into 3 generation. The first generation compounds have simpler side chains ,are the least potent and seldom Used now. The second and third generation compounds have an amino or nitrogenous ring substitution in the side chain, are more potent,have higher efficacy and additional mode of action.
PHARMACOKINETICS:-
BISPHOSPHONATES that is resorbed (from oral preparation) or infused (for intravenous drugs), about 50% is excreted unchanged by the kidney. The remainder has a very high affinity for bone tissue, and is rapidly adsorbed onto the bone surface. Once bisphosphonates are in bone, they have a very long elimination half-life that can exceed ten years .
PHARMACODYNAMIC:-
BISPHOSPHONATES have a very low oral bio avialability . After administration it distributes into soft tissue and bone or is excreted in the urine .
MECHANISM OF Action:-
The mechanism of action of BPNs is not fully understood,but two facets of action have been delineated :
Bisphosphonates are structurally similar to pyrophosphate, but with a central carbon that can have up to two substituents (R1 and R2) instead of an oxygen atom. Because a bisphosphonate group mimics the structure of pyrophosphate, it can inhibit activation of enzymes that utilize pyrophosphate.
The specificity of bisphosphonate -based drugs comes from the two phosphonate groups (and possibly a hydroxyl at R1) that work together to coordinate calcium ions. Bisphosphonate molecules preferentially bind to calcium ions. The largest store of calcium in the human body is in bones, so bisphosphonates accumulate to a high concentration only in bones.
Bisphosphonates, when attached to bone tissue, are released by osteoclasts, the bone cells that break down bone tissue. Bisphosphonate molecules then attach to and enter osteoclasts where they disrupt intracellular enzymatic functions needed for bone resorption.
There are two classes of bisphosphonate compounds: non-nitrogenous (no nitrogen in R2) and nitrogenous (R2 contains nitrogen). The two types of bisphosphonates work differently in killing osteoclasts.
USED:-
prevent the loss of bone density, used to treat osteoporosis and similar diseases. They are the most commonly prescribed drugs used to treat osteoporosis .
SIDE EFFECTS:-
•Fever and flu-like symptoms. ...
•Low levels of calcium in your blood (hypocalcaemia) ...
•Bone and joint pain. ...
•Changes in bowel movements. ...
•Tiredness and low energy levels. ...
•Feeling sick. ...
•Changes to your kidneys. ...
•Irritation of the food pipe (oesophagus)
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