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which may prove advantageous to patients
and health care facilities.
Histomorphometry has shown that
the major effects of pamidronate are to
increase cortical thickness and trabecular
number. Trabecular thickness is not increased.
Bone turnover is significantly reduced
with a decrease in both bone resorption
and formation below that of age matched
normal controls. There was also an increase
in residual calcified cartilage within
the bone.
The safety of bisphosphonate therapy
continues to be of concern. In association
with the first infusion, pamidronate lowers
serum calcium concentrations and leads
to an acute ‘flu-like acute phase reaction
(fever, muscle pain, headache and vomiting).
In vitamin D replete individuals receiving
the recommended calcium intake, the
hypocalcaemia is self remitting. And the
‘flu-like symptoms can be minimized by the
administration of acetaminophen (paracetamol)
or anti-inflammatory medication.
Infants with severe OI and pre-existing
respiratory compromise have been reported
to experience an acute respiratory
distress in associated with the first pamidronate
infusion. This report stresses the
often fragile state of young children with
severe OI and the need for close monitoring
of this cohort during treatment (18).
Pamidronate significantly improved
the growth of children and adolescents
with moderate to severe OI compared
to historical controls over a 4 year treatment
period by preventing limb and spine
deformity. Transient uveitis occurs in
approximately 1% of children who receive
pamidronate (19).
At high doses, pamidronate can interfere
with bone modeling and result in
undertubularization of long-bones. In the
growing skeleton, a reduction in bone
modeling results in the accumulation of
mineralized cartilage, which contributes
to the increase in bone density seen with
pamidronate treatment. Further, acute reductions
in remodeling and the persistence of
calcified cartilage in bone, account for the
characteristic sclerotic metaphyseal lines
seen on long-bone radiographs of children
receiving pamidronate therapy. Suppressed
bone remodeling can also interfere with the
repair of microdamage and may account for
the delay in osteotomy healing (20) and
possibly fracture repair seen in children
with OI who receive pamidronate.
Bisphosphonates are contraindicated
during pregnancy, and all females of reproductive
age should have a negative pregnancy
test before each pamidronate treatment
cycle or before commencing oral
bisphosphonates.
Other issues that can only be addressed
through the continued systematic evaluation
of bisphosphonate therapy in children
and adults with OI are: the long-term benefits
of treatment, the optimal treatment
regime to maximize benefit and minimize
potential long-term side-effects, and the
outcome following cessation of therapy.
IN SUMMARY
1. Cyclic intravenous pamidronate has
good short-term safety and efficacy in
children and adolescents with moderate
to severe osteogenesis imperfecta
and related disorders.
2. Pamidronate therapy should be offered
to children with moderate to severe
OI as defined by: two or more
long-bone fractures per year, and/or
vertebral crush fractures, and/or long-
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