Hi everyone! Welcome back to another lesson. We're talking about the side effects of metformin in
this lesson - so we're going to talk about a brief introduction as to what metformin is, and what
it does, and we're going to talk about the side effects that can happen from taking it, and why
those side effects occur. Let's first talk about what metformin actually is. It is a medication
used to lower or reduce blood glucose levels. So it not only is used for diabetic patients but can
also be used for other patient populations as well including patients with polycystic ovary syndrome.
It lowers blood glucose levels by several mechanisms. One of them is by inhibiting
gluconeogenesis in the liver. Another one is by inhibiting glucose uptake from the
gastrointestinal system, and then another one is by increasing insulin sensitivity. So
by these three mechanisms it can reduce blood glucose levels. Now the problem here is that
metformin may cause a variety of mild and or severe side effects - we're going to talk about
those in this lesson and there are certain patient characteristics that increase the risk of actually
getting side effects from taking metformin and these include the following having liver disease,
having kidney disease, having heart disease, or a recent myocardial infarction, being a heavy
alcohol consumer, and having a previous allergic reaction to metformin. So having these patient
characteristics can increase the likelihood of you having certain side effects from metformin use.
Now let's talk about those side effects from metformin. One of the biggest ones we're going to
see with metformin use is diarrhea. So most times the diarrhea is going to be a watery diarrhea
or a softening of stool, and we can look at this by looking at the bristol stool chart so type 4
is what a normal stool should look like but with metformin we can see type 5, type 6,
and type 7 stool from the bristol stool chart. And diarrhea is so common that it is actually one of
the most common side effects of metformin use. Roughly a third of patients will have diarrhea
from metformin use, and really this percentage is probably even higher than this. And it occurs in a
dose-dependent manner - so oftentimes, metformin is started at a lower dose, patients will get
diarrhea, and then the diarrhea will subside, that side effect will go away, and then the patient's
primary care provider will increase the dose of metformin to a higher dose, and then the
patient will get diarrhea again and then that diarrhea will subside until the therapeutic dose
is reached. So again, what often happens is the side effect of diarrhea will subside and improve
with continued use of metformin, and then the practitioner will increase the dose of metformin,
the patient will get diarrhea again, and then that will subside. Another common side effect of
metformin is flatulence. So this is increased gas and bloating. This often occurs with the diarrhea,
and this too is a common side effect of metformin use. Alternatively, metformin
can cause constipation - this is going to be less common than diarrhea but it can happen in certain
patients - so constipation in this context refers to reduced frequency of bowel movements and or
increased consistency of stool. So again, we can look at the bristol stool chart, type 4
is the normal stool and then with constipation we can see type 1, type 2, and type 3 stool.
So that is going to be something that may occur in some patients who are on metformin. But again,
diarrhea is going to be more common. Now metformin can also cause nausea and vomiting, and nausea and
vomiting is actually one of the most common side effects of metformin use occurring in upwards of
two to three in 10 patients who take metformin. So again, roughly 30 percent of patients are going
to experience nausea and vomiting, so those are going to be the most common symptoms - diarrhea,
abdominal pain along with that diarrhea, and nausea and vomiting. Now a very significant
side effect that can occur with metformin use is lactic acidosis. So lactic acidosis may occur in
certain patient populations taking metformin. This is actually the black box warning with
metformin. So this is the significant condition you want to be aware of when using metformin.
So there are particular patient populations that are at an increased risk for getting lactic
acidosis, and these include those with liver disease, so especially those with cirrhosis,
kidney disease, congestive heart failure, and then those that are on other medications
specifically carbonic anhydrase inhibitors, so topiramate is one of them, and older patients,
patients over the age of 65, and those who are heavy alcohol consumers. So all of those patient
populations are going to be at an increased risk for getting lactic acidosis from metformin use
and then patients who do get lactic acidosis can have symptoms of lactic acidosis including
fatigue respiratory distress among other signs and symptoms - if you want more information
on symptoms of lactic acidosis please check out my full lesson on that topic. Metformin can also
cause heartburn and dyspepsia. So metformin can lead to an increased acid reflux in epigastric
pain and chest discomfort may also occur as well. We can also see dizziness occurring with metformin
use. This may be simply due to taking medication - so a lot of medications when you take them
oftentimes can cause dizziness, it can be a common side effect of many medications,
but it may be due to metformin-induced orthostatic hypotension. So metformin can
lead to orthostatic hypotension so that means that when there's a postural change if someone is going
from sitting down to standing up very quickly they can have a drop in their blood pressure,
and this can cause them to feel dizzy, so that is orthostatic hypotension. So metformin can cause
this and that may be the reason why dizziness can occur in some patients who are on metformin.
Headaches are another possible side effect from metformin use. So they may occur with metformin
use, and again it is a common side effect of many medications like dizziness, headaches can
often be side effects of many medications, but paradoxically, metformin may act to suppress
pain pathways leading to a decreased risk of migraine headaches. So in some patients, it may
cause a headache, but in some other patients it may actually help reduce their migraine headaches.
So this can be a very interesting point to note here. Now another long-term side effect
of metformin use is vitamin b-12 deficiency, and as i just mentioned, deficiency of vitamin b-12 is
associated with long-term use of metformin so a lot of times patients will get on metformin
for their diabetes control, and they'll be on it for a long period of time, but the longer
they are on metformin the more chances that they will become a vitamin b12 deficient.
So because of this they are susceptible to getting signs and symptoms of vitamin b12 deficiency these
include macrocytic anemia, so anemia where the red blood cells are bigger in size,
fatigue and depression are some symptoms that can occur with vitamin b12 deficiency, and then
there are some neurological symptoms from vitamin b12 deficiency including peripheral neuropathy.
Neurological symptoms from vitamin b12 deficiency are very very important to recognize because they
can become irreversible if this is not treated properly. So these neurological symptoms include
peripheral neuropathy but some other symptoms as well including postural stability, two-point
discrimination issues and some other symptoms as well. Again, if you want more information on
vitamin b12 deficiency signs and symptoms, please check out my full lesson on this topic.
Now we can also see a possible side effect of hypoglycemia with metformin use. So hypoglycemia
is a low glucose level, although this is very unlikely to occur as metformin is going to act
to reduce gluconeogenesis and uptake of glucose it's not going to really cause a very low level
of glucose in the blood, but it could in very rare circumstances especially when metformin is
used with other diabetes medications or after excessive alcohol consumption or exercise. So
those are going to be the times when we're going to see metformin possibly causing hypoglycemia,
but most often we're not going to see this as a potential side effect, and with hypoglycemia
we're going to see hypoglycemia symptoms and these include blurry vision and fatigue. Some other side
effects of metformin use include weakness - this is also known as asthenia. So muscle weakness
and fatigue may occur with metformin use. So the muscle weakness and fatigue can be related to the
metformin but could also be related to some other side effects of metformin we've mentioned before
including that vitamin b12 deficiency associated anemia. So that anemia may lead to fatigue as well
so there can be some additional effects from other side effects and with metformin use.
Interestingly, it can increase the risk of certain respiratory infections, particularly an increased
risk of upper respiratory tract infections has been noted in patients on metformin so
upper respiratory tract infections include respiratory tract infections above
the larynx so that means that these are going to be infections in the nose and in the throat,
so we can see an increased risk of respiratory infections with metformin use, but this is an
association, so this doesn't necessarily imply causation but there is an increased association
with respiratory tract infections of the upper respiratory tract in metformin use. Now some
other important side effects of metformin use are taste changes - oftentimes a patient will describe
a metallic taste in the mouth when they're on metformin or they may also have sensation or taste
of acid or sour taste in their mouth which may be related to the heartburn we mentioned earlier
on in this lesson. And then some patients may describe altered or reduced taste so metformin can
cause some taste changes or disturbances either it can reduce or alter the taste of certain foods and
beverages or can lead to a metallic taste in the mouth or have an acid or sour taste in the mouth.
So oftentimes this can be a side effect that a lot of patients on metformin may describe metformin
can also cause myalgia - so myalgia is muscle aches and pains so this can occur with metformin
use and with this muscles may be tender to touch. Diaphoresis is also another side effect of
metformin use. Diaphoresis is excessive sweating. Rhinitis can also occur with metformin use.
So rhinitis is inflammation of the nose and this can lead to a runny nose and nasal congestion,
but this may be a more rare or uncommon side effect of metformin use. So if you want to
learn about other drugs and their side effects please check out my pharmacology playlist,
and if you haven't already please like and subscribe for more lessons like this one.
Thanks for watching and hope to see you next time!