Side effects of Alendronate
The worst side effect of osteonecrosis of the jaw (ONJ), which is rare. ONJ is a side effect of bisphosphonates in general, not just alendronate. There were many lawsuits against Merck alledging ONJ injuries from people who took alendronate when Merck had the patent on it.
A 2008 paper in the Journal of the American Dental Association cast doubts on the alendronate-ONJ connection. The author found that people who took bisphosphonates intravenously had a higher risk of ONJ, but people who took them orally, as most do, had a lower risk. This was based on review of 700,000 medical cases.
Osteonecrosis of the jaw has been recognized for over a century. Indeed, there was an epidemic of Phossy Jaw in the second half of the 19th Century. Even at the time public health practitioners recognized the connection between yellow phosphorus (P4O10) workplace exposure phossy jaw. Hence the name Phossy Jaw.
That epidemic of Phossy Jaw notably affected people who worked in match factories. Matches of the day used yellow phosphorus. It is believed that when the phosphorus oxide gets in the body, it reacts with amino acids and water and carbon dioxide to produce alendronate and other bisphosphonates.
(Contrary to urban legend, no connection has been found between consumption of cola drinks - which contain phosphoric acid - and phossy jaw.)
Other possible side effects
Bone/joint/muscle pain. Somewhat related to ONJ, severe bone and joint has been reported during bisphosphonate treatment. Pain might show up immediately after the medicine is started or in several months later. Doctors have a range of options for dealing with osteoporosis, so be sure to speak up about any pain you experience.
Esophagitis, dysphagia, esophageal ulcers, esophageal erosions, and esophageal stricture have been reported with oral bisphosphonates.
Stress femur fractures - This side effect shows up only after long usage of alendronate. This has only recently been described in the medical literature, and more research is needed to determine how common it is and how much doctors should worry about it.
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Occular side effects (Scleritis and Uveitis) A report in the Canadian Medical Association Journal said that uveitis and sclentis (swelling of the middle and outer eye) were a problem particularly in new users of bisphosphonate drugs. This was a study of a large number of patients..
More of a certain type of fracture? - There was some thought that alendronate decreases the incidence of common fractures, but may actually increase the incidence of less common fractures. A report in the New England Journal of Medicine indicates that is not true.
Hypocalcemia - low calcium level in the blood. Your doctor may have a work-around or put you on a different type of medicine. Slightly lower calcium levels due to alendronate usually poses no problem, but patients who are vitamin D-deficient can get hypocalcemia. Patients taking alendronate should receive at least 1000 mg of elemental calcium and 800 IU of vitamin D per day unless they have hypercalcemia.
Intravenous administration can make the patient feel like he/she has the flu and develop a fever. The white blood cell count may be diminished. This usually passes in a few days.
Some people get stomach cramps or other gastrointestinal problems (gastrointestinal mucosa irritation) on alendronate. While gastrointestinal problems are side effects of many drugs, with some medicines you can reduce these effects by taking the drug with a meal. Unfortunately, absorption of alendronate is poorer with food - this is one reason you shouldn't eat or drink anything for at least 30 minutes after taking the medicine.
Paget's disease patienrs taking 40 mg/day are more apt to get gastrointestinal problems than osteoporosis patients who take one pill per week.
Alendronate has been shown to be easier on the GI track than aspirin.
There is no significant "predictable espophageal, gastric, or duodenal mucosal damage" when the drug is used as directed.