FACTORS INFLUENCING
DRUG ACTION
A
number of factors other than medication itself can affect its action. The
identical drug and dosage may affect different client differently.
l. Developmental factors
·
During pregnancy women must be very
careful about taking medication. It may affect the development of growing
foetus, especially in the first trimester.
·
Most of the drugs are contraindicated
because of the adverse effect on foetus.
·
Infants usually requires a small dosage
because of their body size and immaturity of their organs, especially the liver
and kidney.
·
In adolescence or adulthood, allergic
reactions may occur to drugs formerly tolerated,
·
Older adults may have different response
to medication due to physiological changes that accompany again.
·
Liver and kidney function changes, which
results in the accumulation of drug with in the body.
·
Older adults often experience a decreased
gastric motility, decreased gastric acid production and blood flow which can
impair drug absorption.
·
Older adults may also experience a decreased
number of protein binding sites and change in blood brain barrier. The later
permits fat soluble drugs move rapidly in to the brain causes dizziness and
confusion.
2. Gender
Differences in the way men and women respond
to a medication are chiefly related to the distribution of body fat, fluid and
hormonal differences.
3. Cultural, Ethnic and Genetic variations
·
A client responds to a drug is influence
by age, gender, size and body composition. This variation is known as drug
polymorphism.
·
Drug metabolism is genetically determined
and as a result, race may affect a drug response. This is called genetic
polymorphism.
·
Cultural factors and practices can also
affect a drug action, because of the gene that control liver metabolism vary and
some clients may have a slow metabolism.
·
Certain medications may work well at
therapeutic dosages for some ethnic groups but be toxic for others. E.g.
antipsychotic and anti-anxiety drugs Asian need only lower dosage due to slower
metabolism than that African Americans, Hispanics, & Caucasians.
·
Cultural factors and practices (values and
beliefs) can also affect a drugs action. For e.g. herbal remedies may speed LIP
or slow down the metabolism of prescribed medication
4. Diet
Nutrients can affect the action of a
medication. For an instance, vitamin k in green vegetables can counteract the
effect of an anti-coagulant such as warfarin.
5. Environment
·
The client's environment may affect the
action of drugs, particularly those used to alter mood and behaviour.
·
Environmental temperature may also affect
drug activity. When environmental temperature is high, the peripheral blood
vessels dilate, thus intensifying the action of vasodilators.
·
In contrast, a cold climate and consequent
vasoconstriction inhibit the action of vasodilators, but enhance the action of
vasoconstrictors.
·
A noisy environment may alter the action
of analgesics and sedatives.
6. Psychological factors
A client's expectation about what a. drug
can do can affect the response to the medication. A client, for an instance,
who believes that the codeine is ineffective as an analgesic may experience no
relief from pain after it is given.
7. Illness
and Disease
·
Illness and disease can also affect the
action of a drug.
·
Aspirin can reduce the body temperature of
a fever client, but has no effect on the body temperature of a client without
fever.
·
Drug action is altered in clients with circulatory,
liver or kidney dysfunction.
8. Time of administration
·
The time of administration of oral drugs
affects the relative speed with which they act. Orally administered medications
are absorbed more quickly, if the stomach is empty.
·
Oral medication taken two hours before
meals acts faster than the drug taken after meals.
·
Some medications for e.g. Iron
preparations irritate the gastric tract and need to be given after a meal, when
they will be better tolerated.
·
A client's sleep wake rhythm may affect
the action of a drug.
·
Circadian variations in urine output and
blood circulation for e.g. may affect the client's response to a drug.
COMMENTS