Chemistry of Antibiotics: Cell Wall Synthesis

Introduction

In this post we will continue our exploration of the chemistry of antibiotics with a look at drugs that interrupt wall synthesis and how bacteria develop resistance to these drugs.

The target of these antibiotics is crucial because it explains how antibiotics can attack bacteria without affecting human cells. Bacterial cells, unlike animal cells, have cell walls. Therefore, a drug that attacks cell walls will not be able to impact human cells. Bacterial cell walls are essentially a peptidoglycan layer that is composed of units of peptides (proteins) and glycans (sugars). This layer is the primary and most important component of the cell wall.

β-lactam Antibiotics

The most common class of antibiotics that interferes with cell wall synthesis are the β-lactam antibiotics, which

include penicillin. These types of antibiotics function by impeding the synthesis of the peptidoglycan of the bacterial cell wall. There are multiple ways to inhibit the synthesis of the peptidoglycan layer but the most common is by means of destroying the enzymes that do so. If the antibiotic does not function by destroying synthetic enzymes, it could also destroy the enzymes that convert the polymers into a layer of the cell wall. β-lactam antibiotics inhibit cell wall synthesis by preventing the assembly of the peptidoglycan layer. This is done when the antibiotic competes with the polymer at the site of binding.

This video gives a general overview of how peptidoglycans are inhibited by the mechanisms of a beta-lactam antibiotic:

 The Chemistry of Penicillin

 

Penicillin is one of the most common β-lactam antibiotics, and is characterized by three structural requirements: one fused β-lactam structure, a free carboxylic acid group, and one or more substituted amino acid side chains. Penicillin’s structure prevents the cross linking of peptide chains – weaker cell walls will allow water to flow into the cell freely and the cell will swell and burst, causing cell death. If you change the side R-group chain on the penicillin, the penicillin can possess different properties, such as acidity or penicillinase resistance.

The β-lactam ring in the penicillin reacts with an enzyme that is used for building the cell wall called DD-transpeptidase. Resemblances between a segment of the penicillin structure and the backbone of a peptide chain of the bacterial cell wall have been used to explain the mechanism of beta-lactam antibiotics.

Bacteria Fighting Back

Bacteria have a number of ways to evolve and beat our human antibiotics. One method that bacteria employ in order to fight drugs that interrupt cell wall synthesis, is changing the structure of their cell walls. One instance of this is mutation of pathogenic bacteria. Bacteria that colonize the mucosal pathways, such as nostrils, lips and eyelids, must undergo changes in order to avoid the antimicrobials of the host. In particular, they must avoid lysozyme, an enzyme that destroys the cell walls of bacteria. The activity of lysozyme is similar to β-lactam antibiotics since they both attack the cell walls of bacteria. Since the muramidase activity of lysozyme leads to hydrolysis of the β-1,4 glycosidic bond between the C-1 carbon of N-acetyl muramic acid (MurNAc) and the C-4 carbon of N-acetylglucosamine (GlcNAc), that is the bond that the bacteria have to change in order to survive.Streptococcus pneumoniae and bacillus anthracis, two lysozyme resistant bacteria, have peptidoglycan cell walls that are N-deacetylated, which means that the composition and structure of the sugar component of the cell wall is changed. It was shown that N-acetylating them caused them to be more susceptible to lysozyme. Therefore, it was concluded that N-deacetylating the caused lysozyme resistance. This shows that through changes in structure, bacteria can evade agents that inhibit their cell wall synthesis. When this happens, we too must evolve and change our tactics. This is why new drugs always need to be developed. Bacteria develop resistance, and we must develop new antibiotics.

Want to know more about different classes of antibiotics that inhibit cell wall synthesis? Check out thislink to learn about glycopeptide antibiotics. Of course that’s not enough to satisfy the hunger of your mind, so here is a website that goes further in-depth regarding the processes of cell wall synthesis.

In this post we will discuss antibiotic resistance and how different ‘superbugs’ are being created because of continued use of antibiotics.

Antibiotic resistance is the ability of bacteria to resist the effects of an antibiotic. This usually occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to cure infections. These bacteria survive and continue to multiply, causing more harm. This resistance can cause significant danger for people who have common infections that were once easily treatable with antibiotics. Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply.

Here is an interesting TED Talk by Dr. Karl Klose, which describes the ‘superbug’ and how different bacteria evolve into ‘antibiotic-resistant menaces’.

The big question is how bacteria become resistant to antibiotics. There are two answers to this question. One way that bacteria become resistant to antibiotics is by mutations in DNA. These mutations occur spontaneously and can have two different effects. A change in DNA of bacteria could lead to the prevention of bacterial protein synthesis. In our previous post we discussed how antibiotics target and attack these proteins. However, if the bacteria is active without the protein, there will be nothing for the antibiotics to attack. Mutations causing variations in the shape or size of the protein prevent antibiotics from being able to properly bind to the target protein. Another change in the DNA of bacteria could lead to the overproduction of protein enzymes. This overproduction could lead to various issues. Firstly, a particular dose of antibiotics would not be able to deactivate an overproduction of protein enzymes. Furthermore, some of the proteins produced may be alter the permeability of the cell membrane of cell wall of the bacteria. Aside from spontaneously occurring mutations in the DNA of bacteria, bacteria can become resistant to antibiotics as a result of gene borrowing. According to microbiologist Doctor John Turnidge,  “They’re the original life forms almost, so for thousands of millions of years they’ve had a chance to work out ways to survive and one of those is to borrow genes from other bacteria to survive.” Antibiotic resistance can result from DNA mutations or gene sharing among bacteria. The image below explains how the population of antibiotic resistant bacteria has increased tremendously. For more information regarding the process and causes of antibiotic resistance, check out this website. 

Since the advent of penicillin in the 1940s, antibiotic use has been steadily increasing. Antibiotics are used far more than necessary; they are used as a precautionary measure ‘just in case’ or as a comfort to patients who have viral or fungal infections. According to the CDC, 50 million of the 150 million prescriptions for antibiotics annually are unnecessary. Doctors would rather sign off on a prescription than spend the extra time trying to educate patients on the strengths and weaknesses of antibiotics. In addition to that, increasing use of hand sanitizer and antibacterial cleaning agents also contributes to the development of superbugs. The excessive use of antibiotics has already started to have devastating effects. But why? In the body, antibiotics kill enough bacteria so that the body can finish the job. Shouldn’t more antibiotics just kill more bacteria? It would seem that we should always take antibiotics and heed the adage ‘better safe than sorry’, right? Wrong.

That type of thinking will only drive us towards the edge faster, and here’s why: As soon as researchers develop new antibiotics, there are always already bacteria with the capabilities to defeat them. These resistant bacteria survive the antibiotic agents to multiply and divide, passing on their antibiotic resistanceto their progeny. As a result, the same antibiotics become less effective with time and it becomes harder and harder to develop antibiotics for these so called ‘superbugs’. The most famous strain of bacteria that has risen due to increasing antibiotic use is methicillin-resistant Staphylococcus aureus, or MRSA.

The CDC is currently working to reduce the amount of antibiotics used, because unchecked, it could become a serious public health issue. Already, 2 million people in the US are infected annually by antibiotic resistant bacteria. Should antibiotics continue to be prescribed at such an alarming rate, we could face a post-antibiotic age, in which antibiotics have been rendered useless.

The Mysterious Shortage

If you’ve recently watched NBC Nightly News you may have heard of the impending helium shortage (the topic for our next post), but there is another shortage, perhaps as equally impacting as the helium shortage, that most people have not heard about. That’s because this shortage happens all the time. It is the drug shortage. Where did all the drugs go? They didn’t go to Colorado as some might suspect with the recent legalization of marijuana. These are prescription, FDA-approved drugs that are on shortage, not recreational drugs normally run by drug cartels. But what’s even more interesting is that the drug shortage isn’t a normal shortage. As explained before, these shortages occur all the time, but only to a select number of prescription drugs, and these shortages are much more temporary compared to the helium or Plutonium-238 shortage. Nevertheless, that doesn’t mitigate the impact of this constant shortage. So why is there a drug shortage? As the FDA explains, these drug shortages are due to a number of reasons, most commonly manufacturing or quality problems. As we explore both of these factors, and examples of current drug shortages, you will see how both issues can affect a large population, not tomorrow or in 2025, but now.

To understand a little more about the underpinnings of this unknown shortage, you must first understand how competitive and difficult it is to bring a drug to market. The process often takes a couple of years and a couple billion dollars. The tests for safety are rigorous and lengthy and the paperwork fills dictionaries. It is no wonder why drugs are so expensive and why drug companies will do everything they can to make more money…

So what goes into this testing process regulated by the seemingly “devilish” FDA? Once a company has created a new drug, it can begin the FDA’s Drug Review Process. To start, there are preclinical animal testings. This phase is simply to identify whether the drug is lethal at its prescribed dosage. If it kills a mouse, you certainly do not want to give it to a human. Results must be shown to and reviewed by the FDA before human trials can begin. This transition to human clinical trials is marked by an Investigational New Drug (IND) Application. The first human trial is called Phase 1 where 20-80 healthy patients are given the drug simply to gauge the drug’s safety in humans and discern how the drug is metabolized and excreted. If it is determined that there isn’t an unreasonable toxicity Phase 2 trials begin. Phase 2 tests the effectiveness of the drug compared to placebos in treating a certain ailment. Typically a few dozen to 300 patients partake in Phase 2. If the drug is determined as effective, Phase 3 begins. Phase 3 are mass testings, often with a few thousand participants. This phase tests the drug’s interaction with other drugs and once again the drug is reviewed for its safety and effectiveness. The results are reviewed and finally all phases, trials and results are reviewed in a New Drug Application (NDA). Not so bad? The entire process can take up to 12 years, and drugs have a 1 in 5000 chance of making it through the process.

What does this have to do with the problem at hand? Well, besides bankrupting any small company, the FDA regulates drugs on a much lower frequency once a drug is brought to market with the thought that these drugs are safe. However, this means that your safety is not guaranteed. Often times a demand for a drug will increase, while just as frequently a manufacturing company may close down thereby decreasing supply. This is how a manufacturing and consumerism problem can lead to a shortage. But remember, the drug company just paid, on average, 4 billion dollars to bring that drug to market, there is no way a small manufacturing problem is going to stop the drug company from selling their drug. So what might a drug company do? Come up with a cheaper, more efficiently manufactured formula for the drug and begin manufacturing that. What’s to stop them? The FDA is not due for a visit in another year – hopefully the new formula won’t hurt anyone. And that’s how quality problems arise. A simple change in the formula harms a select, but noticeable, clientele and they report the problem to the FDA. That’s when the FDA’s visit to the drug company is unexpected and a lot sooner than their annual or biannual visit. The FDA will halt all production of the drug, and begin running testings and reviews of the drug once more. So as you can see the two factors – manufacturing and quality – are interlinked and sometimes a drug company will simply pick the lesser of two evils. This makes for a very harmful shortage not only when the formula of the drug is changed, but also in either scenario when production of the drug is slowed or halted and the patientneeding the drug cannot get it.

So what are some current drug shortages, what do the drugs do and who do the shortages affect? An interesting one with many applications is Dexamethasone Sodium Phosphate Injections.

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Dexamethasone is a potent glucocorticoid (the term glucocorticoid is interchangeable with corticoid or corticosteroid) and the injection of Dexamethasone Sodium Phosphate is used to treat allergic reactions, arthritis, blood diseases, breathing problems, eye diseases, intestinal disorders and more. It can also be used to diagnose an adrenal gland disorder (Cushing’s disease) since the adrenal gland is responsible for secreting corticoids. Dexamethasone and other corticoids are anti-inflammatory and is the reason why they can be used to treat ailments like allergic reactions, arthritis or skin disorders (such as bug bites). This is because dexamethasone binds to the glucocorticoid receptor – since they are complementary in structural shape [1] – which is responsible for suppressing the immune system (and heightening awareness). During times of stress, the adrenal gland releases corticoids, which bind to the glucocorticoid receptor. The body suppresses all non-essential functions (i.e. the immune system) and heightens all functions beneficial to survival (i.e. attention). This natural phenomena is used to stop inflammation, a natural immune response. It is also the reason why withdrawing from dexamethasone or any other corticoids can cause weakness and tiredness.

Because of its versatility, the dexamethasone sodium phosphate injection shortage affects many people who need a wide variety of treatments. There are 4 manufacturers of the dexamethasone sodium phosphate injection, but over half of the concentrations of the injection are unavailable from all suppliers. One concentration from a certain supplier may not recover until April, 2014 because of increased demand. Most of these backorders or unavailability began in January of 2013.

Calcium chloride injections are also in shortage, and while they aren’t as widely applicable as Dexamethasone Sodium Phosphate injections, their absence is just as life-threatening. Calcium chloride (CaCl2) is normally a crystal structure as depicted in the below two pictures.

Its crystal structure forms a rather unique cubic unit cell with a total of 2 Calcium atoms and 4 Chloride atoms – appropriately so since there should be twice as many Chloride atoms as there are Calcium atoms. 8 Calcium atoms reside in each corner of the unit cell, and since each contribute 1/8 to the unit cell, that is a total of 1 Calcium atom. Another Calcium atom resides in the center of the unit cell. What makes this unit cell so interesting though is the placement of the Chloride atoms make this cubic unit cell neither a face-centered unit cell nor a body-centered unit cell. 2 Chloride atoms reside completely within the unit cell, while 4 Chloride atoms reside on the faces, each contributing 1/2 to the unit cell which accounts for the 4 total Chloride atoms that are within the cubic unit cell.

As a solid, Calcium chloride is commonly used as brine for refrigeration plants, salt on roads to prevent ice, and desiccation, or the removal of water by chemical means. However as a liquid, the Calcium chloride injection is used for immediate treatment of hypocalcemic tetany, uncontrollable muscle contractions and spasms due to a lack of Calcium in the body, treatment for insect bites, aid for depression due to an overdose of Magnesium sulfate (which happens to be another drug currently on shortage – not because of an increase in overdoses, and the two shortages are not related) and to improve weak or ineffective myocardial  contractions when epinephrine (in injection form is also on shortage. Again, the two shortages are not related) has failed to due so (usually after open heart surgery). Calcium chloride injections are vital to both hypocalcemic tetany, since the cause of the illness is a lack of calcium, and recoveries from open heart surgeries. Again, while both diseases are rare and far less common than the diseases dexamethasone sodium phosphate injections treat, this shortage can have detrimental effects. The shortage began in December of 2012, and still has yet to recover since half the suppliers have either discontinued manufacturing calcium chloride injections, or were having trouble manufacturing enough for the increased demand.

 The final shortage worth touching upon is the copper injection shortage which is often delivered as cupric sulfate (Cu(II)SO4).

This interesting cubic unit cell is even more complex than that of calcium chloride. Again it is neither a simple cubic, face-centered cubic nor body-centered cubic unit cell but rather a combination of them all “plus more”. The copper ions reside in the corners of the unit cell, the edge of the unit cell, the face of the unit cell and in the center of the unit cell. A copper ion resides on each corner and since each contribute one eighth of an ion (8*1/8₎ that amounts to 1 ion. Next there are 4 edge cells which contribute one fourth of an ion (4*1/4) which totals another ion. Then there are 2 face centered ions which each contribute half an ion (2*1/2) which is another ion. Finally there resides one copper ion in the center of the unit cell. In total there are 4 copper ions. Further evaluation of the unit cell concludes in the fact that there are 4 sulfur ions and 16 oxygen ions within the unit cell, or otherwise 4 sulfate (SO₄^-2) ions. This makes sense since the ratio of copper to sulfur to oxygen ions is 1:1:4 and the ratio of copper ions to sulfate ions is 1:1.

Copper injections are used in IV therapies (Intravenous therapies) as a part of total parenteral nutrition (TPN). Copper is necessary, in small quantities, in a human diet and when a patient cannot eat, it is required that they receive their nutrients in another manner; IV therapies. IV therapies are used often in hospitals so this shortage may have a significant impact on hospital patients and is the reason why this may be the most urgent shortage mentioned in this blog. The shortage is not only life threatening to those who need it, but it also affects a large population. The shortage began in April of January and the sole manufacturer has halted production of the injection. The only signs of hope are Cupric Chloride injections, another form of copper injections which are expected to recover from their own shortage sometime this quarter.

Hopefully, as you can begin to see, the fairly unknown drug shortage, is a very serious problem. Luckily most shortages are due to manufacturing delays and not quality problems (perhaps drug companies are not as greedy as the public might believe), but the shortages which can last months, are still detrimental to those who need the drugs. As the problem continues unnoticed by the general public, the best we can hope for is a revamping of manufacturing of dozens of drugs on shortage to satiate the ever-increasing demand for drugs.

Biochemistry of Morphine: How It Can Help and Hurt

In our previous blog post, we discussed the structure of morphine and other opioid analgesics.  These substances all have similar chemical structures, and these structural similarities lead to the similar effects that these opioids have.  In this post, we’ll be specifically discussing the effects of morphine on the body.  From our previous entries, it is known that morphine’s chemical formula is C₁₇H₁₉NO₃.  These elements are organized in a way often called the morphine rule, and other opioids also obey this rule. Additionally, the structures of morphine and the opioids that are derived from it are similar to endorphins and enkephalins, which are substances that the brain naturally produces. These natural substances also have analgesic effects, and since opioids are similar in structure to them, opioids also can stimulate pain receptors in the way that endorphins and enkephalins can. However, since opioids do not have exactly the same structure as endorphins and enkephalins, they are able to cause side effects. Let’s examine some of these effects.

 Biochemistry of Morphine’s Positive Effects

Pain is caused by intense or damaging stimuli. To avoid this unpleasant feeling of pain, people use morphine. Morphine is capable of blocking the pain receptor sites on the nerve cells. It is considered one of the most powerful pain relievers available, but what is the reason behind it being so effective? In this case, since the topic is about the interaction between a chemical and some receptor, there is a lock-and-key mechanism at effect. A molecule which can bind to a receptor is called a ligand, so in this case morphine is a ligand. The circumstances of the ligand being able to bind to the receptor are specific to the size, shape, and charge composition of both. There lies the idea behind the key, the molecule, and the lock, the receptor. If a ligand has the correct structure and charge to fit into a specific site on the receptor, known as the active site, it will bind to the receptor and effect some characteristic of the receptor cell, but we won’t go too deep into that. We’re here to talk about the chemistry of morphine, so let’s take a look at how morphine is the key to blocking pain receptors.

The structure of morphine is reproduced to the right. It is known as acentrally acting analgesic, a category of analgesics that includes opioids and acts on primarily on the brain and spinal cord, making it so capable of being a painkiller. As is apparent from its structure, it contains a benzene ring and various other chemical groups, such as a hydroxyl group and other carbon rings. The morphine needs a specific receptor to bind to in order to be effective. Morphine is known to bind to a specific subset of receptors known as opioid receptors. There are different types of opioid receptors such as kappa (κ)-,mu (μ)-, and delta (δ)- receptors, which differ by functional properties, side effect profiles, genes and proteins, and tissue expression patterns. These receptors are found on nociceptors, the sensory neuron cells that are responsible for sending pain signals to the brain as a response to damaging stimuli. Now that both the key and lock have been defined, the process of binding can take effect. The important characteristic to note in the structure of morphine is that the benzene ring is contained in one plane, so it is completely flat. It is perfect because it is then able to fit snugly against a flat section of the receptor’s active site. The rest of molecule falls into place easily. The neighboring carbon atoms fit into a nearby groove, while the nitrogen atom is able to attach to a negatively-charged group on the receptor, thus binding the ligand to the receptor.

The ligand has been bound to the nociceptor, so the morphine is able to work about dulling the pain. It accomplishes that by simply blocking the pain signals from being sent by the pre-synaptic neuron on the nociceptor. This is done by activating the opioid receptors, causing a reactionary change in the cell, which inhibits the production of substance P, a compound that is responsible for the synaptic transmission of pain and nerve impulses. Refer to the diagram to see a visualization of this process. However, it is a dangerous effect since the slowing of the nerve cell’s function and impulse release could lead to slowing in vital processes such as respiration, resulting in respiratory depression, a negative side effect amongst many.

This diagram is a visual interpretation of the process of blocking the release of substance P by activating opioid receptors, which morphine and endorphins can both do.

 Neurological Side-Effects and Addiction

In addition to stimulating the receptors that process pain signals, morphine is capable of stimulating other regions of the brain, especially the ventral tegmental area of the brain, which processes the release of reward compounds that are released when the human does something that aids survival. Doses of morphine are able to inhibit a process called long-term potentiation, in which the connections between neurons, or synapses, are made stronger through repeated simulation. As a result of long-term potentiation, the brain’s memory capacity is reinforced and made stronger as a result, since strengthened synapses are the basis for memory. Specifically, morphine effects the synapses between inhibitor neurons and dopamine neurons in the ventral tegmental area of the brain.

Pictured here is a dopamine neuron releasing dopamine, depicted as yellow-green circles, to a nearby neuron. Dopamine is responsible for making humans feel “good.”

Dopamine is a reward compound in the brain, being released whenever a human does something that makes them feel good, and inhibitor neurons serve to control the release of dopamine. The morphine removes the link between the inhibitor neuron and the dopamine neurons, so the dopamine neurons produce dopamine uninhibited with the connection to the inhibitor being removed. Thus, the human feels more rewarded since more dopamine is being processed by their receptors, but it takes more dopamine for the human to feel satisfied since the increased dopamine levels of the brain are imprinted into the memory since the morphine stimulates the synapse. Morphine chemically changes the brain by doing this, and it can cause dependence and addiction because of this.

Other Negative Side-Effects

Although morphine and other opioid analgesics primarily work with the brain, some of the side-effects of ingesting these substances affect different areas of the body.  These effects have a variety of causes, and many of these are independent from the structure of the opioid, contrary to the neurological effects.  Similar substances such as morphine, methadone, oxycodone, and hydrocodone can cause serious consequences as side-effects.  Some may even say that these unfortunate effects may render these drugs “not worth it.”  Many of the positive effects of these helpful drugs are only temporary.  For example, when morphine is used as a pain-killer, it is often used for only a short period of time.  The pain is temporary, and once it is relieved, the medication is no longer needed.  However, many of these side-effects are chronic.  As mentioned earlier, addiction can be caused by prolonged usage of opioids.  One’s body becomes trained to require treatment and medication in a process of addiction.  When these substances cease to be taken, the body undergoes withdrawal and many related side-effects.

Pictured here is a woman who is suffering from opioid-induced hyperalgesia after long-term opioid use.

After long-term opioid use, the body can become extra-sensitive to painful stimulation.  This condition is known as opioid-induced hyperalgesia, and although it is induced by nociceptive sensitization in the brain, it affects the entire body.  This state is caused by the inhibition of pain signals, and the alteration of the responsible receptors due to exposure to opioids.  Another long-term side-effect is particularly rampant in males.  This is the lowered production of sex hormones, notably testosterone.  Opioid-induced hypogonadism, as it is called, relates to the inhibition of the endocrine system after long exposure to opioid analgesics.  Consequently, when the body is subject to an imbalance of hormones, a domino-like effect can be caused, and in the case of opioids, people can develop osteoporosis.

These effects, both good and bad, show just some of the things that opioids can do to the human body.  Although these drugs are often used to ward off pain in medical circumstances, if used incorrectly, much like any medication, they can be devastating.  Avoid overdosing or becoming addicted to these substances, and only use them when told by a doctor.  Come back next time to read about methamphetamine, the most abused hard drug in the world, as declared by the U.N. World Drug Report in 2006, and how Heisenberg created it on the hit show Breaking Bad.

Midazolam: The Anesthetic That Makes You Forget

  It is amazing how far medicine has progressed. Can you imagine that only a little over 100 years ago the most common form of treating an illness was bloodletting? Today there are thousands of different medications and drugs available to make a successful treatment. For example, midazolam, often called by its brand name Versed, is a type of oral or injectable drug that is used prior to medical procedures. It is well known for its fast-acting anxiolytic and amnestic properties (MedlinePlus). “I use it for all of my cases from simple hernia operations to complex cardiac procedures…and I imagine [it is used in] over 95% of all cases done in the OR,” says Dr. Kaya Sarier, an anesthesiologist at the Hackensack University Medical Center. This common yet crucial anesthetic causes drowsiness, reduces anxiety, and most interestingly erases the memory of an event. How exactly? Let’s take a closer look.

The Molecule

The molecular formula for midazolam is C₁₈H₁₃ClFN₃. This specific structure with the core of a benzene ring bonded to a diazepine ring allows it to be categorized as a benzodiazepine. If you are interested, this article from the Handbook of Experimental Pharmacology gives a general background on benzodiazepine.

When midazolam is taken, it moves through the body and into the cerebrospinal fluid. There, cytochrome P450 3A4 enzymes metabolize the midazolam. The end product binds to the gamma-aminobutyric acid (GABA) receptor on a neuron. This opens up a channel, and higher concentrations of GABA are released, which bind to the GABA receptors. As a result, this causes chlorine ions to enter the neuron, and the sudden presence of electronegative chlorine ions in the neuron stops the neuron from sending signals to the brain. The neural inhibition that results is the reason why midazolam relaxes the mind and makes you forget the events that transpire under its effects. Check out the animation in this link to see how benzodiazepines react with GABA receptors.

Action Potentials

Now that the general pharmacokinetics of midazolam have been established, let’s compare it to the regular process of a neuron’s response to stimuli. Neurons have a certain point called rest potential, which is the potential difference between two sides of a neuronal membrane when the neuron is not transmitting a signal. The approximate rest potential is -70mV. Neurons naturally respond to events in the environment by depolarization, which starts by the opening of Na⁺ channels. If enough pass through the membrane and reach -55mV, the neuron will proceed to send the signal. This point is called the action threshold. Voltage-gated channels will allow more Na⁺ ions to increase the interior potential to +30mV. Then repolarization starts. The voltage-gated channels of Na⁺ close while those of K⁺ open. The K⁺ ion channels are much slower than the Na⁺ channels, and so more K⁺ions can leave the neuron. The repolarization aims to go back to rest potential, but the process will typically go to -90mV. This is called hyperpolarization. What this does is stops the neuron from receiving and transmitting any other source of stimuli during this time besides the one it is in the process of sending. If hyperpolarization did not occur, the first stimulus that is being sent may change directions and be sent back down the axon to the neuron instead of to the brain; the result would be an unceasing loop of stimuli never being processed and transmitted. The releasing and receiving of K⁺and Na⁺ ions by diffusion eventually bring the neuron back to its rest potential, the stimulus information sent. However, if the interior potential incessantly decreases, the neuron will forever be in hyperpolarization and cease to carry out its functions. A step-by-step description of this process is available on this link and this video as well.

How does this tie into midazolam? Midazolam causes hyperpolarization. The Cl^– ions that are released due to the GABA are brought into the neuron via the GABA receptors. These chlorine ions have a negative charge, causing hyperpolarization in neurons at rest potential and increasing the time needed to send a signal when a neuron is in the process of sending an impulse to the brain. Therefore, the anxiolytic and amnestic effects of midazolam at the correct dosage are not damaging, as all neurons themselves go through hyperpolarization. The main difference is that midazolam causes hyperpolarization in neurons that are not even active, eradicating any chance of an impulse being sent. This is why no stimuli are being received while under the drug’s effects, no memories to remember.

Production of Midazolam

Since midazolam is such a common drug, it is made through a relatively simple process called a condensation reaction. This process is used for producing most benzodiazepine rings, and it involves reacting two amine groups with a ketone. During this reaction, water is lost, classifying it as a condensation reaction. Sulfamic acid is used as a catalyst during the reaction to help the reactants bond and to stabilize the complex.

For the reaction itself, two amine groups bond to the ketone, forming a double bond between the nitrogen and carbon atoms. Then an intramolecular reaction occurs that forms the diazepine ring. The resulting products are benzodiazepine and water. The figure to the below shows the synthesis of a benzodiazepine from o-phenylenediamine.

Drawbacks and the Antidote

While midazolam has its benefits, there are many cases of overdosage due to various factors, such as the patient’s age and metabolism. “The most common side effect would be hypoventilation,” says Dr. Sarier. “This can happen quite often. [The anesthesiologist] would assist in the patient’s ventilation and could administer oxygen via a nasal cannula or place a mask over both the mouth and nose to force oxygen into the lungs.”

In addition to this method, research in the British Journal of Clinical Pharmacology shows that a rising alternative solution is the use of a GABA receptor antagonist/ partial agonist called flumazenil. This drug works by binding to the GABA receptors, thereby reducing the amount of receptors that the midazolam binds to. This reverses the effects of midazolam with proven swiftness of recovering from the side effects. Therefore, flumazenil has been called the “antidote” to any benzodiazepine. For more information on flumazenil, take a look at Netdoctor and PubChem.