Welcome to one of the hardest, if not the hardest sections in pharmacology: neuro and mental health considerations in pharmacology. Not only do we have a lot of drugs to learn, but we don't have a lot of useful stems to fall back on because many drugs have been around a long time. The nervous system is a complicated system with complicated diseases when things go wrong. As such, many of these drugs are used for more than one disorder, making them difficult to categorize. This chapter is a giant puzzle with pieces that don't quite seem to fit at first glance. Nevertheless, let's dive right into this chapter and start putting the pieces together.
OTC Local Anesthetics and Antivertigo
The first drugs we learn about in chapter 5 are the local anesthetics, benzocaine and lidocaine. Both are available OTC as a topical medication, and both have the stem -caine. However, benzocaine is an ester type local anesthetic, while lidocaine is an amide type, this means allergenicity is higher for the ester type because of how it's metabolized. As such, only lidocaine is available as an injection (Rx only) because of its lower chance of causing an allergic reaction. Another drug within this section of the book is meclizine. This drug is also available OTC and helps reduce the feeling of vertigo as its brand name Antivert alludes to. Later in this chapter, we'll learn about an Rx only medication that also treats similar conditions.
Sedatives and Hypnotics
Within this section, we have three different classes of medication. The first one is available OTC and it's just a combination of two drugs we've already learned: acetaminophen and diphenhydramine. We learned that drowsiness is a common side effect for diphenhydramine, but in this case, we are using this drug's side effect as its main purpose. Acetaminophen has no sedating properties, but it does help if patients have any aches or pains keeping them up at night.
The 2nd medication class in this section is the benzodiazepine-like (BZD-like) class. Stems include -clone and -pidem. We'll talk more about real benzodiazepines (BZDs) later in this chapter. Just know these drugs affect the same receptors as real BZDs, but a different subunit of those receptors. BZD-like agents help people fall asleep. To help people stay asleep, a drug like zolpidem has a controlled release formulation. Many BZD-like medications are generally DEA schedule IV.
The 3rd class in this section is the melatonin receptor agonist class. The class name speaks for itself, but we need to understand at least a little about melatonin itself to get the full picture. Melatonin is a hormone that binds to melatonin receptors and regulates our circadian rhythms. Melatonin is OTC, but scientists have developed other agents that selectively bind to these melatonin receptors as well. Look for the stem -melteon to identify a melatonin receptor agonist.
This section is often the hardest sections for students because of subtle differences. There are a many drugs and medication sub-classes and the same stem appears in more than one class (-oxetine). Let's dive right into the first class, the SSRIs. This stands for selective serotonin reuptake inhibitors. Depression has been linked to low levels of serotonin in the brain, so these medications increase the concentrations of this neurotransmitter by blocking the reuptake. Two of the drugs, fluoxetine and paroxetine, share the -oxetine stem.
The next medication class is the serotonin-norepinephrine reuptake inhibitors, or SNRI for short. Norepinephrine is a neurotransmitter too, and it turns out that depression is associated with low levels of it, much like serotonin. This class has just two medications, but one of them is duloxetine. Notice the exact same stem with fluoxetine and paroxetine, yet the drugs are in two different classes.
Next we have the tricyclic antidepressants or TCAs. The organic chemistry representation structure includes three rings, hence the name 'tricyclic'. The first TCAs were introduced years before any SSRI or SNRI, but because of their more prominent side effect profile, TCAs aren't used as much anymore. Amitriptyline. Note the stem -triptyline has the tri- within it. This helps remind you that it's a tricyclic antidepressant.
Finally, we have the MAOIs, or the monoamine oxidase inhibitors. Instead of blocking reuptake, this medication class simply blocks the enzyme that breaks down monoamines like serotonin and norepinephrine. This class was introduced years before the TCAs and their side effect profile is even worse. This class is often reserved as a last case scenario for patients with depression. Isocarboxazid is an example.
Using oral medications to help quit smoking is a relatively new therapy option for patients. We have two drugs to learn here, bupropion and varenicline. Bupropion is also an atypical antidepressant that was rebranded as a smoking cessation tool. Varenicline is solely a smoking cessation agent that was found to be better than bupropion, but comes with more side effects too.
Benzodiazepines work for insomnia too, just like BZD-like medications. However, BZDs also work for other conditions like anxiety and muscle spasms. BZDs have one of two stems: -azepam or -azolam. All BZDs are currently DEA schedule IV.
You may have heard of the drug class called barbiturates, or barbs for short. BZDs have largely replaced barbs for treating anxiety and insomnia. Barbs have a higher potential for abuse and can more easily cause respiratory depression, which can become fatal.
Two DEA schedule II stimulants, methylphenidate and dexmethylphenidate, help ADHD patients focus. No stems here, but the two medications are related. Dexmethylphenidate is the active enantiomer of methylphenidate. So in theory, dexmethylphenidate should be a better drug, although that's not always seen in practice.
Another ADHD is a non-stimulant, non-scheduled class - atomoxetine. Note that this medication shares the same stem with fluoxetine, paroxetine, and duloxetine, but it's not for depression. Be careful when you see an -oxetine stem.
While there are many treatments available for bipolar disorder, one of the most effective is a simple salt on the periodic table of elements: lithium. How it works is not clear, but we know the body has a hard time differentiating sodium from lithium. The therapeutic range of lithium is small, so blood levels are necessary to make sure the patient is neither sub-therapeutic nor toxic.
Schizophrenia agents and antipsychotics are often interchangeable terms. We divide these drugs into: low potency 1st generation, high potency 1st generation, and 2nd generation (also known as atypical). Low potency 1st generation antipsychotics cause more sedation while high potency 1st generation antipsychotics cause more extrapyramidal symptoms (EPS). EPS includes involuntary muscle spasms of the face and extremities, among other movement disorders. Antipsychotics can reduce symptoms of schizophrenia, including hallucinations and delusions. 2nd generation or atypical antipsychotics are less likely to cause EPS but more likely to cause metabolic effects like hyperlipidemia, diabetes, and weight gain.
There are two classes of medication in this section: traditional and newer antiepileptics. Traditional antiepileptics don't have a shared stem, so they can be tough to memorize. Two of the newer antiepileptics have the stem -gab- within them both: gabapentin and pregabalin. Keep in mind these medications have other uses too, like diabetic neuropathy (nerve pain in the hands and feet).
Parkinson's, Alzheimer's, and motion sickness
Parkinson's is a condition with too little dopamine while Alzheimer's is a condition with too little acetylcholine (ACh) in the brain.
A primary Parkinson's drug combination is carbidopa with levodopa. Levodopa is converted into dopamine within the brain. Carbidopa reduces the degradation of levodopa as it travels to the brain. This way, we need a smaller dose of levodopa, reducing the severity of unnecessary side effects like nausea and vomiting. Another medication for Parkinson's is selegiline. Remember the MAOIs for depression? Well, there are two types of monoamine oxidases; MAO-A and MAO-B. Isocarboxazid inhibits both while selegiline only inhibits just MAO-B, the one that degrades dopamine.
For Alzheimer's recall that patients with this disease have low levels of ACh. Donepezil inhibits the enzymes that break ACh down. Selegiline is for dopamine like donepezil is for ACh. Unfortunately, Alzheimer's disease is not that simple; there are many other mechanisms at play. Another medication, memantine, has shown to help slow down the progression of the disease. Keep in mind that we don't have any drugs that cure Alzheimer's. A medication for motion sickness is scopolamine. This works as a patch to put behind one's ear to prevent vertigo and motion sickness while on a cruise ship.
While the content is difficult, the mental health patient population is one that is often underserved. By taking this chapter section-by-section and adding the puzzles pieces one at a time, it should come together.
OTC Local anesthetics and antivertigo
Ester vs amide. Lidocaine is injected.
OTC non-narcotic analgesic / sedative hypnotic
Acetaminophen / diphenhydramine
Using side effect for therapeutic indication
Use CR form if someone has trouble staying asleep
Melatonin receptor agonist
SNRIs - named after neurotransmitters
Be careful of this stem
TCAs - named after structure
MAOIs - named after enzyme it effects
Bupropion - also for depression
Stimulant - Schedule II
Non-stimulant - non-scheduled
Watch out for this stem again
1st generation antipsychotic - low potency
SE - sedation
1st generation antipsychotic - high potency
SE - EPS
2nd generation antipsychotics (atypical)
Atypical have less EPS but more metabolic effects
Both for nerve pain too
Parkinson's, Alzheimer's, and motion sickness
Mem = memory. Done = my memory is done