TABLE 4.

Combination therapies.

Anabolic agents	Anti-resorptive drugs	Methods	Conclusions
PTH (1–84)	Alendronate (Black et al., 2003)	Randomly assigned patients to daily treatment with parathyroid hormone (1–84) (100 µg), alendronate (10 mg), or both for 12 months	i) There was no evidence of synergy between parathyroid hormone and alendronate ii) The anabolic effects of parathyroid hormone may be reduced when use of alendronate simultaneously
PTH (1–84)	Ibandronate (Schafer et al., 2012)	Participants received either 6 months of concurrent PTH and ibandronate, followed by 18 months of ibandronate (concurrent) or two sequential courses of 3 months of PTH followed by 9 months of ibandronate (sequential) over 2 years	i) BMD did not increase more than with either treatment alone ii) Concurrent monthly ibandronate may blunt the effects of PTH(1–84)
Teriparatide	Zoledronic Acid (Cosman et al., 2011)	Randomly assigned patients to receive a single intravenous infusion of zoledronic acid 5 mg plus daily teriparatide 20 mg via subcutaneous injection, zoledronic acid alone, or placebo infusion plus daily teriparatide 20 mg for 1 year	A beneficial effect of co-administration of teriparatide and zoledronic acid treatment was shown as compared to teriparatide or zoledronic acid monotherapy
Teriparatide	Denosumab (Tsai et al., 2013; Tsai et al., 2019)	Patients were assigned in a 1:1:1 ratio to receive 20 µg teriparatide daily, 60 mg denosumab every 6 months, or both	Combined teriparatide and denosumab increased BMD more than either agent alone
		Participants were randomly assigned (1:1) to receive teriparatide 20 µg (standard dose) or 40 µg (high dose) daily for 9 months. At 3 months, both groups were started on denosumab 60 mg every 6 months for 12 months	Combined treatment with teriparatide 40 µg and denosumab increased BMD more than standard combination therapy