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Clinical
Research Trials
Clinical
research trials: The Mater hospital has become a designated
centre to parcipatate in a multi-centre, multinational clinical
research study involving oral sildenafil.
The
purpose and objectives of the research study
The primary
objective of the project is to evaluate the effect of oral
sildenafil (20,40,80mg tid) on exercise capacity, as measured
by the six minute walk test (see
investigations), after 12 weeks of treatment, and also
to assess the safety, tolerability of the same three doses
in subjects with pulmonary arterial hypertension who are aged
18 years an over during the 12 week period.
An additional aspect of the study will involve the collection
storage and use of blood samples to investigate possible associations
between genetic variation, in relation to response to sildenafil,
and in relation to characteristics of pulmonary arterial;
hypertension.
Sildenafil (viagra):
This agent is a PDE5 inhibitor thought to reduce pulmonary
artery pressure and pulmonary vascular resistance.
Mode
of action:Nitric oxide dilates pulmonary blood vessels
by stimulating intracellular guanylate cyclase, thereby elevating
intracellular cyclic guanine monophosphate (cgmp) in pulmonary
arterial vascular smooth muscle cells.
Elevated
Cgmp reduces levels of intracellular calcium and thereby causes
relaxation of these smooth muscle cells and ultimately reductions
in pulmonary artery pressure and pulmonary vascular resistance.
Sildenafil
acts by inhibiting the breakdown of Cgmp through PDE5, an
enzyme that metabolises intracellular Cgmp to inactivate 5
GMP, found in human pulmonary arteries.
Mode
of administration: Sildenafil is by oral administration
in tablet form. Commencement dose is tid
Side effects: Headache, Flushing, Dizziness, Digestive
interruption-Dyspepsia, Nasal congestion Altered vision -
This is usually mild and transient, predominately colour tinge
to vision, but also increased perception to light or blurred
vision. Muscle ache, Priapism, Adverse reactions were mild
to moderate in nature and the incidence and severity increased
with dose.
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