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P A R T 8
Drugs acting on the cardiovascular system
BOX 48.1
Drug therapy across the lifespan
Drugs affecting blood coagulation
CHILDREN
Little research is available on the use of anticoagulants in
children. If they are used, the child needs to be monitored
very carefully to avoid excessive bleeding related to
drug interactions or alterations in gastrointestinal or
liver function. People who interact with the child need
to understand the importance of preventing injuries and
providing safety precautions.They should be aware of
what to do if the child is injured and begins to bleed.
If heparin is used, the dose should be carefully
calculated based on weight and age and checked by
another person before being administered.
Warfarin is used with children who are to undergo
cardiac surgery. Again, the dose must be determined
based on weight and age, and the child should be
monitored closely.
The safety of low-molecular-weight heparins has not
been established in children.
At this time, there are no indications for the use of
antiplatelet or thrombolytic drugs with children.
ADULTS
Adults receiving these drugs need to be instructed in
ways to prevent injury—such as using an electric razor
instead of a straight razor, using a soft-bristled toothbrush
to protect the gums, and avoiding contact sports—and
instructed in what to do if bleeding does occur (apply
constant, firm pressure and contact a healthcare provider).
They should receive a written list of signs of bleeding to
watch for and to report to their healthcare provider.
Because so many drugs and alternative therapies are
known to interact with these agents, it is very important
that these people be urged to report the use of this drug
to any other healthcare provider and to consult with one
before using any over-the-counter drugs or alternative
therapies.
It is prudent to advise any person using one of these
drugs in the home setting to carry or wear a MedicAlert
notification in case of emergency.
The person also needs to understand the importance of
regular, periodic blood tests to evaluate the effects of the
drug.
PREGNANCY AND BREASTFEEDING
Because of the many risks associated with increased
bleeding or increased blood clotting during pregnancy,
these drugs should not be used during pregnancy unless
the benefit to the mother clearly outweighs the potential
risk to the fetus and to the mother at delivery. Risks of
altered blood clotting in the neonate make these drugs
generally inadvisable for use during breastfeeding.
OLDER ADULTS
Older adults may have many underlying medical
conditions that require the need for drugs that alter blood
clotting (e.g. coronary artery disease, cerebrovascular
accident, peripheral vascular disease, transient ischaemic
attacks). Statistically, older adults also take more
medications, making them more likely to encounter
drug–drug interactions associated with these drugs.The
older adult is also more likely to have impaired liver and
kidney function, conditions that can alter the metabolism
and excretion of these drugs.
The older adult should be carefully evaluated for
liver and kidney function, use of other medications, and
ability to follow through with regular blood testing and
medical evaluation before therapy begins.Therapy should
be started at the lowest possible level and adjusted
accordingly after the person’s response has been noted.
Careful attention needs to be given to the person’s total
drug regimen. Starting, stopping or changing the dose
of another drug may alter the body’s metabolism of the
drug that is being used to affect coagulation, leading to
increased risk of bleeding or ineffective anticoagulation.
Blood vessel injury
Platelet adhesion
to wall of injured
vessel and platelet
aggregation
Platelet plug
↓
Blood loss at site of injury
Loss of blood
into tissues
↑
Extravascular
pressure
Compression of
injured blood vessel
Intrinsic pathway
to clot formation
Extrinsic pathway
to clot formation
Blood clot
Blood vessel
constricts
↓
Blood flow
at site of injury
FIGURE 48.1
Process of blood
coagulation.
