Hi. Welcome to our video on
or you probably know them
by their name, penicillins.
So, this would be the 1 group
of medications you
probably have already been exposed to
or even taken yourself
before you started your nursing program.
Let's roll into these drugs and
how we use them in a setting.
Now. they're called Beta-Lactam Antibiotics
because of the ring that they have.
See that the drug on the left, penicillin,
and the other drug, cephalosporins,
they have a Beta-lactam ring.
Now, don't get worried.
We're not going to ask you to
draw the chemical formulas
or molecules for these drugs.
I just wanted you to understand
why they're called
Now there's 4 major sub-classes
of Beta-lactam antibiotics.
There's penicillins, cephalosporins,
carbapenems, and monobactams.
Now, the reason that you care about this
is because Beta-lactam antibiotics
have the small chance of having
So, if a patient is allergic to penicillin,
there's a very small chance, like < 5% chance,
that they would have a cross
allergy to a cephalosporin.
So, in an NCLEX test question and
like we say, in NCLEX world,
if I know my patient has
a penicillin allergy,
then I also would not want to give
them a cephalosporin.
Now, let me give you an example of
how a test question may come up.
You may see something that says,
"Your physician has the following
orders for your patients.
Which one of the orders requires
immediate follow up?"
Well, if I knew my patient had
a penicillin allergy
and they had listed any cephalosporins
in the answer choices,
that would be the one I
would go for. Because
they both have Beta-lactam rings,
and even though there is
a very small chance
that there could be a cross
allergy, in NCLEX world,
we wouldn't give that drug, and that's why
we would contact the healthcare provider.
So, let's start talking about the penicillins.
If you've watched our other video
on sulfonamides, you know that
they were introduced in the 1930s.
Now, penicillins came along in
the 1940s and these
really were a game changer.
Now they're bactericidal.
Remember, that's a cell killer that
kills those bacteria,
and how they do that is they
inhibit cell wall synthesis.
So, if that cell wall isn't
complete and intact,
that bacteria is going to die.
But penicillins are active
only against bacteria
that are undergoing growth and division,
so we've got to get that drug in
there, and they can attack
when the cell is undergoing
growth and division.
Now, penicillins are broad spectrum,
so they kill a wide variety of bacteria.
emember, our goal is to try and
keep you on the most
narrow spectrum to help deal
with microbial resistance.
Now, you'll see the picture of the
inventor of penicillin there,
we thought we'd give him a little shout out,
a little props as we're going through this.
There's some classifications of penicillins.
The first 2 deal with the narrow
and 1 group of them, penicillinase sensitive,
and the other group is
So I've got examples of the drug
names there for you.
Penicillin G and penicillin V
are penicillinase sensitive.
That means that they're not very
good in treating those bugs
because the penicillinase destroys them.
I'll talk to you a little bit more
about that later,
but just kind of get in your mind
we have narrow spectrum penicillins.
Some are sensitive to the
and some are resistant to those enzymes.
Obviously, 1 of the drugs, the nafcillin,
oxacillin, or dicloxacillin
is going to be our choice
because it's penicillinase resistant.
Now, I'll explain why that sounds different
than we're looking at culture and
sensitivity in just a minute.
Now, the third and fourth groups deal
with broad-spectrum penicillins
and extended-spectrum penicillins.
So, broad-spectrum penicillins are
like ampicillin or amoxicillin,
and lots of times, you see these
prescribed for pediatric patients.
Piperacilin is an even more
So when we're looking at the
classifications of penicillins,
I want you to, kind of, have just in
mind, for frame of reference,
4 variables: narrow spectrum, penicillinase
sensitive, penicillinase resistant,
broad-spectrum, and extended-
Okay, so let's look at that
mechanism of action.
You'll see in your notes that you have
that little icon that will remind you
that the mechanism of action is it
weakens the bacterial cell wall.
So, use that as a little trigger for
your brain to remember that
that is the mechanism of action
of these medications.
So, the penicillin enter the bacteria
through their cell wall.
Now, once the penicillin
gets inside that cell,
they bind to penicillin-binding protein.
Yay. Just stop for a minute and celebrate
something -- its name, so it makes
perfect sense on what it does.
bind with the penicillin once
it's inside the wall,
and then once they're bound, that
cell wall synthesis becomes
abnormal, it's disrupted.
Well, that might not sound like
such a big deal to you,
but it's a big deal because when you
disrupt normal cell wall synthesis,
the bacteria cells will die from –
boom -- cell lysis.
So, penicillins don't kill other
cells in the body,
but they sure take care of business
with the bacteria.
So, walk through that with
me again 1 more time.
I give my patient penicillin.
Penicillin will actually enter the
bacteria through the cell wall.
Then the penicillin will bind with
the penicillin-binding proteins,
and once it's bound, that cell wall
isn't complete anymore,
and they end up with lysis.
All of the good stuff
squishes out of the bug and it's dead.
And that's why penicillin is considered
a bactericidal antibiotic.
Okay, now. We've put together
some really cool things
to help you remember the key
points about penicillin.
Look at the P.
They penetrate the cell wall and
they're protein binding.
That's awesome. So, you've got
step 1 and step 2 right there.
P for penicillin, penetrate, and
Then look at the C. It makes the
cell wall weak and leaky.
And L, causes a lysis of the cell.
So this kind of method works for your
brain and I encourage you to
put a circle by this or star
this to know that
penicillin penetrates the cell wall,
then the cell wall becomes weak and leaky,
and there's a lysis of the cell.