Hi! My name is Jill Beavers-Kirby, and today,
we're going to be talking about
some common dosage calculations. So, what
are some of the routine medication
administration schedules, or what are the
most common times that we give the
medicines? So, a couple of abbreviations
that you're going to see routinely
throughout your career as a nurse are things
like AC. It can be a capital A and a
capital C or a lower case a and a lower case
c, which means, before meals, Ad lib is
BID is twice a day. PC is after meals.
PRN is as needed. QID is four times a day.
STAT means immediately. QAM means every
morning. Q2H means every two
hours. Q4H means every four hours.
Couple of medication abbreviation
times that you should
not use and you should not see is one, QD,
which in the old days make Q day, but now, we don't like to
use that because it can cause confusion.
So instead of writing QD, we will see
daily. You want to use that instead of QD.
So, what are some words that you have to
know when you're giving medications? One is onset.
This is the time that it takes
a medication after it's given to start taking
effect. The peak time of a
medication is when the medication reaches its
highest concentration in the
The trough, it is the opposite of the peak.
It's the point at which the medication
is at its lowest level of effect in the body.
You'll want to use trough times four
dosing medications such as antibiotics, such
as vancomycin. You'll want to trough
time to know if you need to change the dose
of the medication so that they're
getting a steady state of the medication
throughout their blood system.
Another term you'll see is duration. This is
simply how long the medication is going to
be effective in the system. So,
the duration of a
medication may be as short as 30 seconds
such as adenosine, or as long as 24 hours
such as some chemotherapy.
And finally, plateau. This is when the serum
concentration of a medication has
reached its highest and maintains that same
level. So, you'll see plateaus used
for things like dosing of warfarin, also
known as Coumadin. So you have to have
about three doses of Coumadin in your system
before you can get a steady state
or plateau in your system.
So, how do we give medication? Couple of you're probably
already familiar with, oral by mouth, pills that you
can swallow, pills that you can put under your tongue which
is called sublingual, or buccal, that's the
inside of the cheek area, or
parenteral, that includes subcutaneous which
is in the layer of skin,
intramuscular which is in the muscle,
intravenous or epidural. There's also
some topical medications. These go
directly on the skin. The most common
one you'll probably see are things like
topical steroids for rashes or
nitroglycerin patches for people with angina.
You can also give medications by
inhalation. You usually see this with people with
respiratory issues such as people
with asthma or COPD, when they're asked to inhale a
bronchodilator so that it helps
get their lungs open. And finally, mucous membranes,
this includes, eye such as
eye drops, ear such as ear drops, nose such
as afrin or something else that
you squirt in your nose. It also includes
the vaginal suppositories,
rectal suppositories, or for some people who
can't take anything by mouth and they
have an ostomy, you can also give medications
through their ostomy side.
So, as with everything, there's good and bad.
What are the pros and cons of certain
rounds of medication administration?
So the oral route,
well, it's easy, it's convenient. However,
might be difficult for some people to swallow
these pills or liquids, they might taste terrible.
and if your patient has nausea and vomiting
or something else going on with their GI tract,
they're not going to absorb it very well.
Parenteral route is a good route.
That's the IV route, the subcutaneous route, the IM route.
These are also easy, convenient.
However, you're risking infection because
you're breaking the skin. Can be painful for some patients.
Some people are just
scared, absolutely petrified of getting stuck with
the needle, and in that case, the
parenteral route probably isn't a good choice for
them. Topical routes are also
painless. They're pretty easy to do, and less side
effects. However, if the
skin is broken or thin, you might get a different
expectation of absorption.
In other words, the lotion might go all up and down
the arm if the skin is ripped in
and transports the lotion that way. Or if there is
an area of broken skin, the lotion
might burn, or the cream or whatever you're putting
on. You might burn the patient.
The mucosal route is nice because it's readily
absorbable. However, it can cause
some local irritation. So, it can cause the mucosal
site to get red or a little raw
on the patient and they might not prefer that. Or
if it's rectal or vaginal, it
might not be easy for the patient to give for
themselves. The inhalation route is
really good for patients, like I said, with
respiratory problems, with breathing
problems, because that way, they can breathe in
the medicine, the medicine goes in pretty
quickly and it starts to affect them pretty quickly.
However, because you're
inhaling it, it might cause systemic side effects.
For example, a lot of the
bronchodilators can cause your heart rate to
increase, which kind of makes
people a little nervous and jittery for about
the first ten minutes after they
take this medication. Some patients don't like
that and it's very uncomfortable for
them. So, how do we measure our medicine?
How do we measure what we're
giving the patient? Well, the most common, most
accurate system is the metric
system. This is most widely used
and this is pretty common in hospitals, doctors
offices, clinics everywhere you go.
So there's things like grams, liters, milliliters,
milligrams, and these are all
very specific measurements. Old system
measurement is called the apothecary
system. These were things like a dram which
I still don't know what that means
because I've never seen it used. But it's a very
old system. It was not standardized. We don't
use it to measure out medications today.
However, we do still slip in household
measurements. You will see some medications
written as, give one teaspoon
or give one tablespoon or drink the entire
gallon. We will mix this
with the metric system. So it does get a little
confusing at times but just kind of keep in
the back of your mind that one teaspoon equals
five milliliters, a tablespoon equals 15
milliliters, and so on. You just kind of
have to remember that. So speaking
of conversions, here are some of the
common conversions. As I said, a
tablespoon is 15 milliliters. A kilogram
equals 2.2 pounds. Some medications are
going to be based on X amount of drug per
kilogram. They don't say X amount of
drug per pounds. So you have to know how to
convert pounds and kilograms.So, a
thousand milligrams is a gram, 500 milligrams
is 0.5 grams, a thousand milliliters
is a liter, and so on.
So the most common formula that you're going to use to
figure out drug calculation is called ratio
and proportion. It's kind of a
reminder back to high school math. So for
example, on the screen we have
5:10 = 1:2. So that's saying five is to
ten as one is to two. If you
remember, the first and last numbers of
that equation are called the extremes.
The middle numbers are called the mean. So you
multiply the means times the
extremes to come up with your
answer. So for example, 250 milligrams of
the drug is in 5 ml of a
solution. You need to give the patient
100 milligrams. So, how many mls do
we need to give? So we know that there's
250 milligrams in 5 ml.
We need to give 100 milligrams is to
X ml. We don't know what
the X is. So we multiply our means by
our extremes, and we get 250x = 100 x 5.
Do the math. Xs are being 2 mls of the drug.
So if you just kind of think about
that, you know that the 2 ml is less than
5 ml and there's 250
milligrams in 5 ml and you need to give
less than that.
So 2 is the right answer and you've just done
a kind of a little immediate self-check
in your brain. So, what are the rights of
Anytime you give a patient a medication,
any and every single time you give a
patient a medication, you need to ask
yourself these five rights. Do I have
the right medicine? Do I have the right dose?
Do I have the right patient? And do I have
the right route? And am I giving it at the right time?
Every single time you give the
patient a medicine, you should go through
these five rights. If one of these is
incorrect and you still give the medication,
it's considered a medication
error. Every single time you give a medicine,
ask these little five
rights in your head every single time. So, what
are the elements of a medication
order? A medication order has to be very specific
in order for you to give it as the nurse.
One, it has to have the patient's name. Two,
it has to have the patient date and time
that the order is written. It has to have the
name of the medication on it, has to
have the dose. If it doesn't have all those,
you can't take it as a medication order.
You have to have the route of the administration,
the time and frequency
that you're going to give it, and the
signature of the prescriber. So for
Joe Smith takes one 350 milligram Tylenol
tablet every six hours as needed by
mouth, signed by Jane Doe. If it doesn't
have all of those elements, it's not a
complete medication order and you can't give
it. You can't just make up one of
the elements and think you can give the
medication. You need to contact the
prescriber and say, how often do you want
the patient to have this? How did you
want the patient to get this? Did you want
them to take it by mouth or as a
suppository? All of these elements have
to be there. You as a nurse cannot make
these decisions independently. Thank you.
This has been Jill Beavers-Kirby
discussing dosage calculations.