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Low bone mineral density (BMD) was observed at baseline in approximately 10% of individuals receiving TD*/FTC for PrEP in the IPREX study (29). Individuals should be counselled about the effects of TD* on BMD and counselled to decrease alcohol and cigarette use, to undertake weight-bearing exercise and ensure their diet provides adequate amounts of calcium and vitamin D (30). A clinician may suspect that an individual is vitamin D deficient and may wish to test their vitamin D levels. There is no evidence that over-the-counter vitamin D supplements reduce tenofovir-related BMD changes.

A small but statistically significant decline in BMD was observed by week 24 in participants of the iPrEX study. The decline in BMD correlated directly with levels of intracellular TD*-DP and was found to be reversible once PrEP was ceased (31).

There are no data available on whether on-demand^† PrEP is less likely to cause a decline in BMD.

Recent data from the DISCOVER study, found that TAF/FTC versus TDF/FTC was associated with less decline in BMD (21).

A person with a history of osteoporosis will require careful monitoring while on PrEP. If the clinician suspects that a person may have osteoporosis, they may recommend BMD testing. BMD testing is rebated in Australia under specific clinical circumstances; information about BMD rebates can be found at: www.health.gov.au/internet/main/publishing.nsf/content/diagnosticimaging-bd.htm. In those people over the age of 40 years thought to be at risk of having reduced BMD, a FRAX® tool to evaluate fracture risk can be used to assess the need for dual-energy X-ray absorptiometry (DXA) scanning. For further information see https://www.sheffield.ac.uk/FRAX/tool.aspx?country=31.

^† The Therapeutic Goods Administration (TGA) has not approved this regimen in Australia.