Alendronate is a Bisphosphonate.
It is a third generation product of this group of drugs
Others in the class include :
Pamidronate (Novartis) also a third generation product 
Etidronate (a first generation product).
Risedronate (Actonel)
These drugs are used for:
1. Hypercalcaemia of malignancy
2. Pagets disease and
3. Osteoporosis.

The latter was treated in the past using Etidronate, but this caused problems with bone mineralization and therefore was used in doses of 2 weeks every few months.
With the new generation products including alendronate and palmidronate, we don’t have this problem and alendronate is used daily ongoing.
The drug binds strongly to the bone surface, and then inhibits the action of the Osteoclast cell (which resorbs or removes bone in the bone life-cycle). The osteoblast-which lays down new bone therefore deposits new bone in excess of that resorbed.
As a result then is a net Formation of bone. The result is an Increase in bone mass. This therefore potentially reverses the progression of osteoporosis.

Alendronate has a potential to cause esophageal ulceration and dyspepsia, or indigestion. You have to take it on waking in the morning, on an empty stomach, and with a full glass of water. YOU MUST NOT EAT OR TAKE ANYTHING BUT WATER FOR A FULL HALF HOUR or the drug will bind to the food and therefore not be effective. In addition, you should not lie flat after taking the tablet, and should preferably get out of bed and stay upright. This minimizes risk of esophageal ulceration.

In fact palmidronate has a probable higher potential for esophageal ulceration, and it is therefore used by myself only in an intravenous form as an infusion.

Calcium is still required approx 1gram / day.
The Calcium must be taken at NIGHT or BED TIME.
The drug may increase bone mass approx 4-6% in the first two years.
It is supposed to be an ongoing drug.

I usually monitor the effects of it by checking a bone dexa scan densitometry at baseline and after 12-18 months.

If you have osteoporosis-----ask your doctor.

I have found this group of drugs useful for treatment of symptomatic as well as asymptomatic osteoporosis.

I have found that with the use of Calcitonin and these Bisphosphonates used appropriately, that the crippling effects of spinal fractures is a thing of the past, and that my patients are almost fully mobile after 1 month ---without pain killers.

In the old days, a spinal fracture meant prolonged bed rest and the use of powerful pain-killers. My personal regimen for patients with spinal fractures, is to use pamidronate - Aredia - (Novartis) as a single intravenous pulse - 30mg in 400 ml saline over 4 hours intravenously. This is extremely useful in spinal fractures - with excellent pain relief. The patient is usually given 3 daily injections of miacalcic 100 units subcutaneously for three days, and gets the pamidronate on day 4. Thereafter, the patient is mobilized with physical therapy. The patient usually is able to stop all analgesia by day 10-14. The Pamidronate is then given as an intravenous infusion every 6 months. In fact the infusion is done as an outpatient, and is approximately 33% less expensive than oral alendronate, which I personally do not find effective for bone pain.

I have personally - had excellent results with this regimen, with fantastic pain relief and early mobilization of the patient. None of my patients have required ongoing opiate analgesia, with this protocol.

Not all primary care physicians are aware of these new category medications.
If you have to -- educate them---there is a lot of help available for osteoporosis.