The FDA posted an alert on Monday regarding possible severe, sometimes incapacitating bone, joint, and/or muscle pain in patients taking a class of bone-density drugs called bisphosphonates.

The possibility of such pain is listed in the drugs' prescribing information, but the FDA warned that doctors may overlook it to the point that it's prolonged or results in impairment, possibly requiring analgesics. This pain can occur days, months or years after initial use, and the risk factors for and incidence of severe musculoskeletal pain associated with the class are still unknown, according to the agency.

"Healthcare professionals should consider whether bisphosphonate use might be responsible for severe musculoskeletal pain in patients who present with these symptoms and consider temporary or permanent discontinuation of the drug," noted the health regulator in a Med Watch post on Monday.

The class of bone drugs in question include:

Proctor & Gamble's ( PG) Actonel, Actonel +Ca, and Didronel

Novartis' ( NVS) Aredia, Reclast and Zometa

Roche and GlaxoSmithKline's ( GSK) Boniva

Merck's ( MRK) Foxamax, Fosamax + D

Sanofi Aventis' ( SNY) Skelid.