For full information on prescription medicines for osteoporosis, got to www.medsafe.govt.nz

Calcium

Our bodies use calcium for many reasons, including function of nerves and muscles, and blood clotting. If we don’t have enough calcium for these needs we’re in trouble because our bodies will start drawing calcium from our own bones. The result: weak, easily broken bones. That is why it is important to make sure we have enough calcium, either by eating calcium-rich foods or by taking calcium supplements.

Bone consists mainly of collagen protein fibres, with calcium and phosphate between these fibres to give strength and rigidity. The amount of collagen present, and therefore the amount of bone, depends on the balance between two types of cells - bone forming cells and bone resorbing cells. If our calcium supply is inadequate to meet all the body’s demands our bone resorbing cells will move into action, redistributing calcium from bones to other parts of the body.

Dairy products, including low fat dairy foods that contain good levels of calcium include: milk, cheese, yoghurt and ice cream. In most western countries older people consume 500mg to 1000mg of calcium each day, but research shows that an additional 500mg to 1000mg of calcium daily can slow bone loss significantly. That would require at least four to six servings of calcium-rich foods every day. Many older people may feel uncomfortable eating those quantities and instead prefer to take calcium supplements.

The recommended dosage for older people at risk of osteoporosis is 500mg to 1000mg daily as a supplement. Calcium is available in many forms, and there is some evidence (and some disagreement) that suggests that soluble calcium supplements are more readily absorbed than less soluble salts, such as calcium carbonate.

Calcium alone will not completely stop bone loss, but it can slow it down.

Vitamin D

Calcium can only be fully absorbed if the body has enough vitamin D. Unlike other vitamins, vitamin D comes not from food, but is made in the skin as a result of direct exposure to sunlight. Many elderly people lack Vitamin D because they don’t spend enough time outside in the sun, but fortunately Vitamin D can be taken as a supplement.

A daily dose of 500-1000 units can be taken as cod liver oil, halibut liver oil or multivitamin tablets. Alternatively, you take a convenient, once-a-month Vitamin D tablet of 50,000 units of calciferol.

If you are concerned about Vitamin D, ask your doctor for a simple blood test that will measure your levels.

Calcitriol

Calcitriol, produced in the kidneys, is the most active naturally occurring form of Vitamin D. It regulates the absorption of calcium from the diet. It has been used for the treatment of osteoporosis in a few countries (including Australia and New Zealand).

Small beneficial effects on bone density have been shown in some trials, but these are much less than the effects of hormone replacement therapy or the bisphosphonates. The effects of calcitriol on fracture numbers are unclear, with one trial suggesting that it decreased the number of fractures, while a second trial suggested that fracture numbers actually increased. Since more effective therapies are now available these are generally preferred.

Hormone Replacement Therapy (HRT)

After menopause all women experience a decline in bone density. This is directly linked to the lower levels of sex hormones produced by the ovaries. Hormone replacement therapy (HRT) - the administration of ovarian sex hormones, or similar compounds - can restore a woman’s hormones to pre-menopausal levels.

Oestrogen is the particular hormone that influences bone density. However, most women who take HRT take a combination of oestrogen and progesterone, because the progesterone protects the womb against cancer. If oestrogen is given on its own for many years to women who still have a womb, irregular bleeding can occur and the risk of cancer in the lining of the womb increases. If a woman has had a hysterectomy, she requires only the oestrogen.

The combination of oestrogen and progesterone can be given either as one tablet daily or as separate tablets or stick-on patches The hormones can be given either in a cycle, resulting in a monthly menstrual-type period, or they can be given continuously, resulting in no periods.

If a woman starts HRT at the time of menopause she will prevent postmenopausal bone loss, and the associated loss of height often experienced by older women. The risk of fractures developing over the next five to 10 years will also be substantially reduced. However, even if HRT is not started until many years after menopause, it still appears to increase bone density and reduce fractures.

For more information on HRT, click here.

Recent studies into the balance of risks and benefits with HRT means that HRT is no longer recommended as the first choice treatment for osteoporosis in women.

Selective Oestrogen Receptor Modulators (SERMs)

This is a new treatment for osteoporosis, with few side effects. In some tissues it mimics the effects of oestrogen, while in other tissues it blocks the actions of oestrogen. This pattern of effects varies from one SERM to another. The only SERM currently available for osteoporosis treatment is raloxifene.

Raloxifene mimics the effects of oestrogen on bone, however its impact on bone density is not as great as the use of oestrogen itself. It has been shown to reduce the number of fractures in the spinal column, but does not appear to influence frequency of fractures in other parts of the body, for example, the hip. Neither does raloxifene have the beneficial effects of oestrogen on hot flushes.

However, a recent four-year trial showed that by opposing the effects of oestrogen on the breast, it substantially reduced the number of new breast cancers.

Bisphosphonates

Bisphosphonates are phosphate salts that bind to the bone surface and help prevent the activity of bone resorbing cells. Not only do they prevent further bone loss and reduce the number of fractures, but during the first few years of use they can actually increase bone density. Bisphosphonates are the most intensively studied group of treatments for osteoporosis. Three medicines in this class are:

• Etidronate, the first bisphosphonate to be used, and the least potent. It can increase spinal bone density by two to three per cent. Trials indicate that it reduces the number of spinal fractures, but there is no definite evidence that it reduces the incidence of fractures in other parts of the body.
  Etidronate is taken as a course of tablets lasting two weeks, and repeated every three months.
• Alendronate increases bone density in the spine by five to six per cent in the first two years. After seven years this rises to 10%. In patients with osteoporosis, alendronate has been shown to halve the number of new fractures in the spine, hip and forearm.
  In the past, alendronate has been taken daily, but now appears just as effective if taken in a larger dose once a week. It sometimes causes heartburn or other forms of indigestion, particularly if dosing instructions are not followed carefully (see below).
• Risedronate is the newest bisphosphonate in clinical use. Its effects on bone density and reduction in fractures are similar to those of alendronate. Risedronate is taken as a daily tablet. It is too early to determine its side effect profile, but in developmental trials there were few side effects.

Dosing instructions – caution, very insoluble

Bisphosphonates are extremely insoluble, so dosing instructions must be followed precisely to ensure that the maximum amount is absorbed.

• Take the dose first thing in the morning with a full glass of water, at least half an hour before eating.
• Water only: The tablets should be taken only with water, as milk, tea, coffee or fruit juice interfere with their absorption.
• Remain upright (sitting or standing) for at least half an hour after taking the tablet. This prevents it sliding back into the oesophagus, where it may cause irritation and heartburn.
• Do not take calcium tablets at the same time of day.

Thiazide diuretics

These have been used for many years for treating high blood pressure or fluid retention. One of their side effects is that they reduce the amount of calcium lost in the urine, resulting in small increases in bone density. They are not effective enough to be used as a sole therapy for osteoporosis, but can be useful when used in conjunction with other medicines.

Calcitonin

Calcitonin, a hormone, is produced by the thyroid gland in the neck. While it reduces the activity of the bone resorbing cells, it is less effective than other treatments, and is not available in New Zealand for use in osteoporosis. Whether it prevents fractures remains controversial.

Administration must be by injection or nasal spray, because calcitonin is digested if taken by mouth.

Fluoride

Fluoride salts have been used in the past for treating osteoporosis. Clearly, they can increase bone density, but this is not always paralleled by a reduction in the number of new fractures. Some evidence suggests that higher doses can interfere with the normal structure and strength of bone.

As a result of these concerns, fluoride is no longer widely used for osteoporosis, although it is possible that low doses in combination with other treatments, such as hormone replacement therapy, may be effective.

Source: Ian Reid, Professor of Medicine at the University of Auckland, and an endocrinologist at Auckland Hospital and at Auckland Bone Density.

Original material supplied by LivingWith.