LSB384 Lecture Notes - Lecture 2: Methoxyflurane, Beclometasone Dipropionate, Glucocorticoid
Comparison of Routes of Administration
• Focusing on advantages & disadvantages
Oral vs Intravenous
Oral
Intravenous
Safe
Has to be done with professional
D
Convenient
Have to keep the vein open
D
Affected by 1st pass liver
metabolism
Not affected by 1st pass liver metabolism
A
Bioavailability will be lower e.g.
pethidine at 25% after oral
administration
Bioavailability 100% e.g. pethidine at
100% after IV injection
A
Some drugs may not be active
after oral administration e.g.
ionized drugs, peptides
Soe drugs that are’t active after oral
administration could be with IV e.g.
ionized drugs, peptides
A
Some drugs irritate lining of
intestinal mucosa e.g. cytotoxic
anti-cancer drugs
Does not irritate lining of intestinal
mucosa & inner lining of blood vessels are
quite insensitive e.g. cytotoxic anti-cancer
drugs
A
No immediacy – has to be
absorbed & distributed
Immediacy & accuracy, straight into
circulation – e.g. when there is need to
sedate subject quickly
e.g.
A
Not suitable when there is
emesis
Fine with emesis
A
Drugs need to lipophilic to be
absorbed
Not suitable for drugs in oily vehicles or
precipitates haemolysis
D
Time lag to remove drugs that
are incorrectly administered
Actions not easily reversed
D
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2
Oral vs Subcutaneous
Oral
Subcutaneous
Convenient & safe
Requires injection into fat
D
Some drugs not active after oral
administration, as it is
subjected to the digestive
pathways too e.g. insulin
Those drugs are suitable for subcutaneous
administration
A
First pass liver metabolism
Avoids first pass liver metabolism –
released into circulation (rather than into
portal vein)
A
Slow release preparations are
available
Provides a slow release preparation for
ongoing effects
A
Rate of absorption may be
variable e.g. exercise, CV
disease
Rate of absorption can be varied e.g.
soluble insulin (rapidly) vs insoluble insulin
(slowly). Done by altering pH or particle
size
A
Area affected by subcutaneous
administration can be limited by
vasoconstrictor e.g. adrenaline, keep the
drug localised
A
Oral vs Rectal
Oral
Rectal
Convenient
Not convenient (up rectum)
D
Cannot be administered
when there is emesis e.g.
diazepam
Can be administered with emesis (by HCW
or parent) e.g. diazepam
In fact, drugs such as prochlorperazine can
be used to stop emetic symptoms
A
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Document Summary
Comparison of routes of administration: focusing on advantages & disadvantages. Bioavailability will be lower e. g. pethidine at 25% after oral administration. Some drugs may not be active after oral administration e. g. ionized drugs, peptides. Some drugs irritate lining of intestinal mucosa e. g. cytotoxic anti-cancer drugs. No immediacy has to be absorbed & distributed. Time lag to remove drugs that are incorrectly administered. So(cid:373)e drugs that are(cid:374)"t active after oral administration could be with iv e. g. ionized drugs, peptides. Does not irritate lining of intestinal mucosa & inner lining of blood vessels are quite insensitive e. g. cytotoxic anti-cancer drugs. Immediacy & accuracy, straight into circulation e. g. when there is need to sedate subject quickly e. g. fine with emesis. Not suitable for drugs in oily vehicles or precipitates haemolysis. Some drugs not active after oral administration, as it is subjected to the digestive pathways too e. g. insulin. Rate of absorption may be variable e. g. exercise, cv disease.
