Bone drugs: the basics

We can take preventative measures to help our bones, but if we lose enough bone tissue there’ll be a conversation about medication. Here’s a rundown on the most common types.

There are two main types of bone drugs — the ‘anti-resorptives’ that reduce bone breakdown, and anabolic medications that promote new bone growth.

The ones we’re most familiar with belong in the first category.

I’ve said this before, so apologies for the repetition, but bone is constantly formed and reformed throughout our lives. We have cells that create new bone and cells that remove old bone. When we’re younger we build more bone that we lose. After menopause this can turn around so we lose more bone than we build.

Anti-resorptive medications bring the balance back in favour of the bone building cells, mostly by reducing the activity of the bone removal cells.

Within this category are a class of medications called bisphosphonates. GPs’ first choice of drugs for treating low bone density are a couple of bisphosphonates called Fosamax and Actonel. (I’ll stick with brand names because that’s what we’re most familiar with.)

These are taken orally. There’s not much difference between Fosamax and Actonel, but some women might respond to one better than the other.

Most women have no issues taking them, but reflux or nausea are the most common side-effects. You need to take them on an empty stomach to make sure they’re well absorbed.

Aclasta is also a bisphosphonate, but it’s given as an annual infusion. It was used more widely a few years ago, but another anti-resorptive — Prolia — seems to have taken its place (and Prolia has been shown to be more effective).

Prolia is administered via an injection every six months. Although it also reduces bone breakdown, it works in a different way to the bisphosphonates.

It’s possible to take a break (called a ‘drug holiday’) from Fosamax or Actonel if you’ve taken one of those continuously for three to five years. There’s been debate about how long these breaks should be, and it probably depends on factors such as a patient’s bone density and their risk of falling.

But a study published in 2021 found that within 12 months of not taking Fosamax some women showed a modest loss of bone. The researchers saw this more in younger women (late 40s, 50s), and further research will hopefully spell out more about how to manage drug holidays.

Prolia wears off quickly after five or six months though, and the risk of vertebral fractures increases soon after that time. If you’ve been on Prolia for several years and your doctor decides it’s time to go off it, they’ll switch you to another medication (probably a bisphosphonate) so you don’t lose the advantage you’ve gained.

The most frequently reported side-effects from Prolia are low blood calcium levels and muscle aches, though I’ve heard endocrinologists say they haven’t come across either.

The key anabolic medications are Forteo or Terrosa and Evenity. These are given via injection and are used for people with severe osteoporosis or when other medications haven’t worked.

Forteo and Terrosa require doing this daily (they’re self-administered) and are only effective for two years. Evenity is expensive and has been linked to cardiovascular problems. Which is why they’re not widely used.

Of course, many women become concerned after hearing that bone medications can cause two unpleasant side effects — osteonecrosis (death of bone tissue) of the jaw and fracture of the thigh bone.

These are rare but can occur in women who’ve used medications for many years. Osteonecrosis is more likely in cancer patients who are on high drug use, people with poor oral hygiene, and smokers.

The thigh bone fracture can occur after prolonged suppression of the bone removal cells.

To reiterate, both conditions are rare. Make sure you know the possible side-effects of whatever you’re using though.

While bone medications are effective in increasing bone density, we need to be clear that no medication (or anything else) can entirely prevent fractures or works for everyone.

It’s also important to recognise that no matter what bone medication we’re using, we need exercise to improve our balance, strength, and mobility, and reduce our risk of falling.

In addition, a healthy diet that includes sufficient calcium and protein will support the formation of good quality bone.

What’s encouraging is that scientists always seem to be working on new drugs in this area. For example, some are looking at whether it’s viable to use stem cells to speed up recovery from fractures.

Another team, from the University of Birmingham, have shown that a peptide (a small protein) that occurs naturally in our bodies can be used to increase bone formation and strength. Their work is largely still at the stage of animal testing, but it looks promising.

Whereas medications such as the bisphosphonates block the action of the cells that break down and remove bone, this peptide boosts bone building while also allowing the cells that do the breakdown to get rid of weak or damaged bone. Watch this space.

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