Ibandronic acid (INN) or ibandronate sodium (USAN) is a potent bisphosphonate drug developed by Hoffman La Roche and used in the prevention and treatment of osteoporosis and metastasis-associated skeletal fractures in people with cancer. Ibandronate is indicated for the treatment and prevention of osteoporosis in post-menopausal women. In May 2003, the U.S. Food and Drug Administration (FDA) approved Ibandronate as a daily treatment for post-menopausal osteoporosis. The basis for this approval was a three-year, randomized, double-blind, placebo-controlled trial women with post-menopausal osteoporosis. Every participant also received daily oral doses of calcium and 400IUs [international units] of vitamin D. At the study's conclusion, both doses significantly reduced the occurrence risk of new vertebral fractures by 50–52 percent when compared to the effects of the placebo drug. Ibandronate is efficacious for the prevention of metastasis-related bone fractures in multiple myeloma, breast cancer, and certain other cancers. In 2008, the U.S Food and Drug Administration (FDA) issued a communication warning of the possibility of severe and sometimes incapacitating bone, joint and/or muscle pain.[4] A study conducted by the American Society of Bone and Mineral Research concluded that long-term use of bisphosphonates, including Boniva, may increase the risk of a rare but serious fracture of the femur. Ibandronic acid is marketed under the trade names Boniva in the USA, Bondronat in Europe, Bonviva in Asia, Ibandrix in Ecuador and Bondrova in Bangladesh.

Risedronic acid is a pyridinyl bisphosphonate that inhibits osteoclast-mediated bone resorption and modulates bone metabolism. The action of risedronate on bone tissue is based partly on its affinity for hydroxyapatite, which is part of the mineral matrix of bone. Risedronate also targets farnesyl pyrophosphate (FPP) synthase. It is FDA approved for the treatment of postmenopausal osteoporosis, osteoporosis in men, glucocorticoid-induced osteoporosis and Paget’s disease. Calcium, antacids, or oral medications containing divalent cations interfere with the absorption of Risedronic acid. Common adverse reactions include rash, abdominal pain, constipation, diarrhea, indigestion, nausea, backache, urinary tract infectious disease and influenza-like illness.

Alendronic acid is a bisphosphonate drug used for osteoporosis, osteogenesis imperfecta, and several other bone diseases. It is marketed alone as well as in combination with vitamin D. Alendronate inhibits osteoclast-mediated bone-resorption. Like all bisphosphonates, it is chemically related to inorganic pyrophosphate, the endogenous regulator of bone turnover. But while pyrophosphate inhibits both osteoclastic bone resorption and the mineralization of the bone newly formed by osteoblasts, alendronate specifically inhibits bone resorption without any effect on mineralization at pharmacologically achievable doses. Its inhibition of bone-resorption is dose-dependent and approximately 1,000 times stronger than the equimolar effect of the first bisphosphonate drug, etidronate. Under therapy, normal bone tissue develops, and alendronate is deposited in the bone-matrix in a pharmacologically inactive form. For optimal action, enough calcium and vitamin D are needed in the body in order to promote normal bone development. Hypocalcemia should, therefore, be corrected before starting therapy. Treatment of post-menopausal women and people with osteogenesis imperfecta over the age of 22 with alendronic acid has demonstrated normalization of the rate of bone turnover, significant increase in BMD (bone mineral density) of the spine, hip, wrist and total body, and significant reductions in the risk of vertebral (spine) fractures, wrist fractures, hip fractures, and all non-vertebral fractures. In the Fracture Intervention Trial, the women with the highest risk of fracture (by virtue of pre-existing vertebral fractures) were treated with Fosamax 5 mg/day for two years followed by 10 mg/day for the third year. This resulted in approximately 50% reductions in fractures of the spine, hip, and wrist compared with the control group taking placebos. Both groups also took calcium and vitamin D.

Pamidronic acid (Pamidronate Disodium) is a bone resorption inhibitor. The principal pharmacologic action of pamidronate disodium is inhibition of bone resorption. Although the mechanism of antiresorptive action is not completely understood, several factors are thought to contribute to this action. Pamidronate disodium adsorbs to calcium phosphate (hydroxyapatite) crystals in bone and may directly block dissolution of this mineral component of bone. In vitro studies also suggest that inhibition of osteoclast activity contributes to inhibition of bone resorption. In animal studies, at doses recommended for the treatment of hypercalcemia, pamidronate disodium inhibits bone resorption apparently without inhibiting bone formation and mineralization. Of relevance to the treatment of hypercalcemia of malignancy is the finding that pamidronate disodium inhibits the accelerated bone resorption that results from osteoclast hyperactivity induced by various tumors in animal studies. Pamidronate disodium, in conjunction with adequate hydration, is indicated for the treatment of moderate or severe hypercalcemia associated with malignancy, with or without bone metastases. Pamidronate disodium is indicated for the treatment of patients with moderate to severe Paget’s disease of bone. Pamidronate disodium is indicated, in conjunction with standard antineoplastic therapy, for the treatment of osteolytic bone metastases of breast cancer and osteolytic lesions of multiple myeloma.

Cholecalciferol (/ˌkoʊləkælˈsɪfərɒl/) (vitamin D3) is one of the five forms of vitamin D. Cholecalciferol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, in mineralization of bone, and for the assimilation of Vitamin A. The classical manifestation of vitamin D deficiency is rickets, which is seen in children and results in bony deformities including bowed long bones. Most people meet at least some of their vitamin D needs through exposure to sunlight. Ultraviolet (UV) B radiation with a wavelength of 290–320 nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes vitamin D3. In supplements and fortified foods, vitamin D is available in two forms, D2 (ergocalciferol) and D3 (cholecalciferol) that differ chemically only in their side-chain structure. Vitamin D2 is manufactured by the UV irradiation of ergosterol in yeast, and vitamin D3 is manufactured by the irradiation of 7-dehydrocholesterol from lanolin and the chemical conversion of cholesterol. The two forms have traditionally been regarded as equivalent based on their ability to cure rickets and, indeed, most steps involved in the metabolism and actions of vitamin D2 and vitamin D3 are identical. Both forms (as well as vitamin D in foods and from cutaneous synthesis) effectively raise serum 25(OH) D levels. Firm conclusions about any different effects of these two forms of vitamin D cannot be drawn. However, it appears that at nutritional doses, vitamins D2 and D3 are equivalent, but at high doses, vitamin D2 is less potent. The American Academy of Pediatrics (AAP) recommends that exclusively and partially breastfed infants receive supplements of 400 IU/day of vitamin D shortly after birth and continue to receive these supplements until they are weaned and consume ≥1,000 mL/day of vitamin D-fortified formula or whole milk. Cholecalciferol is used in diet supplementary to treat Vitamin D Deficiency. Cholecalciferol is inactive: it is converted to its active form by two hydroxylations: the first in the liver, the second in the kidney, to form calcitriol, whose action is mediated by the vitamin D receptor, a nuclear receptor which regulates the synthesis of hundreds of enzymes and is present in virtually every cell in the body. Calcitriol increases the serum calcium concentrations by increasing GI absorption of phosphorus and calcium, increasing osteoclastic resorption, and increasing distal renal tubular reabsorption of calcium. Calcitriol appears to promote intestinal absorption of calcium through binding to the vitamin D receptor in the mucosal cytoplasm of the intestine. Subsequently, calcium is absorbed through formation of a calcium-binding protein.

Tiludronic acid is a bisphosphonate characterized by a (4-chlorophenylthio) group on the carbon atom of the basic P-C-P structure common to all bisphosphonates. Tiludronate is a first generation (non-nitrogenous) bisphosphonate in the same family as etidronate and clodronate. Tiludronate affects calcium metabolism and inhibits bone resorption and soft tissue calcification. Of the tiludronate 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 absorbed onto the bone surface. Tiludronic acid is marketed under the tradename Skelid. In vitro studies indicate that tiludronate disodium acts primarily on bone through a mechanism that involves inhibition of osteoclastic activity with a probable reduction in the enzymatic and transport processes that lead to resorption of the mineralized matrix. Bone resorption occurs following recruitment, activation, and polarization of osteoclasts. Tiludronate disodium appears to inhibit osteoclasts through at least two mechanisms: disruption of the cytoskeletal ring structure, possibly by inhibition of protein-tyrosine-phosphatase, thus leading to detachment of osteoclasts from the bone surface and the inhibition of the osteoclastic proton pump. SKELID is indicated for treatment of Paget's disease of bone (osteitis deformans).

Etidronate is a salt of etidronic acid (brand name Didronel, also known as EHDP) a diphosphonate, which is indicated for the treatment of symptomatic Paget’s disease of bone and in the prevention and treatment of heterotopic ossification following total hip replacement or due to spinal cord injury. Didronel is not approved for the treatment of osteoporosis. This drugs acts primarily on bone. It can inhibit the formation, growth, and dissolution of hydroxyapatite crystals and their amorphous precursors by chemisorption to calcium phosphate surfaces. Inhibition of crystal resorption occurs at lower doses than are required to inhibit crystal growth. Both effects increase as the dose increases. Preclinical studies indicate etidronate disodium does not cross the blood-brain barrier. Didronel is not metabolized. The amount of drug absorbed after an oral dose is approximately 3 percent. Bisphosphonates, when attached to bone tissue, are absorbed by osteoclasts, the bone cells that breaks down bone tissue. Although the mechanism of action of non-nitrogenous bisphosphonates has not been fully elucidated, available data suggest that they bind strongly to hydroxyapatite crystals in the bone matrix, preferentially at the sites of increased bone turnover and inhibit the formation and dissolution of the crystals. Other actions may include direct inhibition of mature osteoclast function, promotion of osteoclast apoptosis, and interference with osteoblast-mediated osteoclast activation. Etidronic acid may promote osteoclast apoptosis by competing with adenosine triphosphate (ATP) in the cellular energy metabolism. The osteoclast initiates apoptosis and dies, leading to an overall decrease in the breakdown of bone.

Clodronate (also known as clodronic acid) is a drug used to treat a high level of calcium in the blood caused by changes in the body that happen with cancer. Clodronate is approved in some countries and is sold under trade trade name bonefos for oral use. Bonefos is indicated in the management of osteolytic lesions, hypercalcemia and bone pain associated with skeletal metastases in patients with carcinoma of the breast or multiple myeloma. Bonefos is also indicated for the maintenance of clinically acceptable serum calcium levels in patients with hypercalcemia of malignancy initially treated with an intravenous bisphosphonate. Bonefos forms complexes with divalent metal ions, and therefore simultaneous administration with food, antacids and mineral supplements may impair absorption. It was suggested, that the mechanism of action of clodronate was involved osteoclast apoptosis.

Alfacalcidol (1-hydroxyvitamin D3) is a synthetic analog of vitamin D introduced clinically in the early 1970s. A prodrug for calcitriol (1,25-dihydroxyvitamin D3), it is one of the most potent and rapidly acting compounds currently used in the prevention and treatment of vitamin D deficiency states and hypocalcemia. The clinical benefit of alfacalcidol is related to the stimulation of calcium and phosphorus absorption, reversal of myopathy, promotion of mineralization in bone and the ability to reabsorb fully mineralized bone. Similar marketed vitamin D compounds include calcitriol and ergocalciferol. Alfacalcidol is indicated in conditions where there is a disturbance of calcium metabolism due to impaired 1-α hydroxylation such as when there is reduced renal function.

Ipriflavone (chemical structure: 7-isopropoxyisoflavone), derived from the soy isoflavone, daidzein, holds great promise for osteoporosis prevention and treatment. Ipriflavone (IP) was discovered in the 1930s but has only recently begun to be embraced by the medical community in this country. Over 150 studies on safety and effectiveness, both animal and human, have been conducted in Italy, Hungary, and Japan. As of 1997, 2,769 patients had been treated a total of 3,132 patient years. Preliminary studies have pointed to its effectiveness in the treatment of other conditions involving bone pathology, including Paget’s disease, hyperparathyroidism, renal osteodystrophy, and tinnitus due to otosclerosis. Ipriflavone appears to have several mechanisms of action, all of which enhance bone density, making them seemingly superior to many of the other treatments available for osteoporosis prevention and treatment. IP also inhibits osteoclastic activity (motility and resorptive activity) by modulating intracellular free calcium. IP’s bone-forming mechanisms include stimulation of cell proliferation and maturation of osteoblasts by inhibiting calcium influx into osteoblasts and phosphoinositide hydrolysis. Despite similarities to estrogen, IP possesses no intrinsic estrogenic activity, but does potentiate estrogen. Importantly, IP does not change bone mineral composition or crystalline structure. A clinical trial reported in 2001 that it was not effective in prevention or treatment of osteoporosis.