Home' Australian Pharmacist : January 2011 Contents Vol. 30 -- January #01
Continuing Professional Development
The articles in this series are independently researched and compiled by PSA commissioned authors and peer reviewed.
protecting against the onset of type 1
and type 2 diabetes.12,13,26,27
As well, recent studies have:
• Suggested a possible beneficial role
of vitamin D in cognitive function.
Vitamin D receptors are present
in areas of the brain involved in
complex planning, processing,
and forming new memories.
Neuroprotective functions of
vitamin D are thought to include
neuronal calcium regulation,
nerve conduction and detoxification
mechanisms. There is evidence that
vitamin D has a beneficial role in the
developing brain as well as in adult
• Found that, in people with
asthma, reduced vitamin D levels
were associated with impaired
lung function, increased airway
hyperresponsiveness and reduced
response to corticosteroids.29
• Found that vitamin D has
a protective effect against
Vitamin D deficiency
Causes of vitamin D deficiency
• Inadequate intake or synthesis:
-- Inadequate sunlight exposure.
-- Reduced synthesis from a given
UVB exposure (e.g. the elderly).
-- Inadequate consumption of
foods containing vitamin D.
• Reduced absorption:
-- Small bowel disorders,
e.g. coeliac disease; sprue;
inflammatory bowel disorders;
infiltrative disorders (lymphoma,
-- Pancreatic insufficiency,
e.g. chronic pancreatitis,
-- Biliary obstruction, e.g. primary
biliary cirrhosis, external
• Abnormal metabolism (defects
in the production of 25(OH)D or
-- Chronic hepatic disorders,
e.g. hepatitis, cirrhosis.
• Resistance to effects of vitamin D:
-- Type II hereditary vitamin
D-dependent rickets due to
mutations in the 1,25(OH)2D
receptor. In this disorder,
1,25(OH)2D is abundant but
ineffective because the receptor
is not functional.
People at risk of vitamin D deficiency
• Older people, especially those who
are institutionalised or housebound.
• Dark-skinned people
(particularly if veiled).
• Breast-fed infants of women with
vitamin D deficiency.
• Pregnant women (particularly if dark
skinned or veiled).
• People who are obese (vitamin D is
fat soluble and is stored in adipose
tissue; low serum 25(OH)D levels
in obese people are believed to be
due to vitamin D sequestration by
• People taking drugs which can
cause vitamin D deficiency.
• Rapidly-growing adolescents and
young children (especially in winter).
• People with intestinal, renal or
Signs and symptoms of vitamin D
• Bone discomfort or pain (often
throbbing) in the lower back, pelvis
• Muscle aches.
• Muscle weakness.
• Symmetrical lower back pain in
• Increase in body sway and falls.
Serum 25(OH)D is used to assess
vitamin D status, as it is produced
from both dietary and cutaneous
sources of the vitamin. The optimal
serum 25(OH)D level for adults
is >50 nmol/L (preferably about
75 nmol/L). Some researchers
recommend levels of 75--100 nmol/L,
especially for the elderly. Although an
optimal paediatric level has not yet
been specified, infants, neonates and
young children with a 25(OH)D level
<27.5 nmol/L are considered to be
vitamin D deficient.1,33
Vitamin D deficiency in adults is
classified according to the following
serum 25(OH)D levels:1,2,32
• Mild: 25--50 nmol/L.
• Moderate: 12.5--25 nmol/L.
• Severe: <12.5 nmol/L.
Other biochemical markers which may
aid in assessment of vitamin D status
include elevated serum levels of
alkaline phosphatase and parathyroid
Table 1. Stages of vitamin D deficiency11
Vitamin D and
Some medicines can cause or
exacerbate vitamin D deficiency.
• Corticosteroids -- reduce calcium
absorption and impair production
of biologically-active vitamin D.
• CYP450 inducers
(e.g. carbamazepine, isoniazid,
primidone, rifampin) -- induce
hepatic conversion of vitamin D
to inactive metabolites and
reduce circulating levels of active
• Orlistat and cholestyramine --
reduce absorption of vitamin D
(and other fat-soluble vitamins).
There is an increased risk of
hypercalcaemia if vitamin D is given
with thiazide diuretics and calcium,
and plasma calcium concentrations
should be monitored.38
High doses of vitamin D
should be given with caution to
patients taking digoxin, because
hypercalcaemia (which may
result from excess vitamin D use)
may precipitate abnormal heart
evidence in patient care
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