Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

A Brodmann area in the brain is defined by cytoarchitecture, histology and organization of cells:
Primary Sensory 3,1,2
Primary Motor 4
Premotor 6
Primary Visual 17
Primary Auditory 41
Brocas 44

Semorinemab is a potential treatment for dementia that works by targeting the N-terminal region of the tau protein. By binding to tau, it aims to reduce its spread within neurons and slow down the progression of the disease.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Renal Impairment and Psychotropic Drugs

The following table provides recommendations for drug treatment in patients with renal impairment, based on the Maudsley 14th guidelines. When a new drug treatment is required, the suggestions below should be followed.

Drug Group Recommendation

Antipsychotics: It is recommended to avoid sulpiride and amisulpride. Otherwise, no agent is clearly preferable to another. For first-generation antipsychotics, haloperidol (2-6 mg/day) is the best choice. For second-generation antipsychotics, olanzapine (5mg/day) is the best choice.

Antidepressants: No agent is clearly preferable to another. Reasonable choices include sertraline (although there is poor efficacy data in renal disease), citalopram (with care over QTc prolongation), and fluoxetine (with care over long half-life).

Mood stabilizers: Lithium is nephrotoxic and contraindicated in severe renal impairment. Otherwise, no agent is clearly preferable to another. Valproate of lamotrigine are suggested.

Anxiolytics: No agent is clearly preferable to another. Lorazepam and zopiclone are suggested.

Anti-dementia drugs: No agent is clearly preferable to another. Rivastigmine is suggested.

Hallucinations and Illusions

Hallucinations can take on different forms, including reflex hallucinations, auditory hallucinations, and functional hallucinations. Reflex hallucinations occur when a stimulus in one sensory modality produces a hallucination in another. For example, someone may smell oranges when they hear music. Auditory hallucinations, on the other hand, are the presence of auditory experiences in the absence of a true stimulus. Functional hallucinations occur when an external stimulus provokes a hallucination, and the normal perception of the external stimulus and the hallucinatory experience are in the same modality.

In addition to hallucinations, there are also illusions, which involve false perceptions with sensory distortions. Kinaesthetic hallucinations are a type of hallucination that involve bodily movements. Understanding the different types of hallucinations and illusions can help individuals better recognize and manage these experiences.

The pontine tegmentum also known as dorsal pons is located within the brain stem. Several cranial nerve nuclei are located in the pontine tegmentum. The nuclei of CN V, CN VI, CN VII and CNVIII are located in the pontine tegmentum.

Narrow Therapeutic Index Drugs

Narrow therapeutic index (NTI) drugs are medications that have a small difference between the amount that causes a therapeutic effect and the amount that causes toxicity. In other words, the therapeutic index (TI) of these drugs is narrow. The TI is a ratio that compares the blood concentration at which a drug causes a therapeutic effect to the amount that causes death of toxicity.

In clinical practice, the TI is the range of doses at which a medication appeared to be effective in clinical trials for a median of participants without unacceptable adverse effects. For most drugs, this range is wide enough, and the maximum plasma concentration of the drug achieved when the recommended doses of a drug are prescribed lie sufficiently above the minimum therapeutic concentration and sufficiently below the toxic concentration.

However, some drugs have a narrow therapeutic index, which means that even small changes in dose of blood concentration can lead to serious adverse effects. The US Food and Drug Administration (FDA) defines a drug product as having an NTI when there is less than a twofold difference in the minimum toxic concentrations and minimum effective concentrations in the blood and safe and effective use of the drug requires careful titration and patient monitoring.

Examples of drugs with a narrow therapeutic index include carbamazepine, lithium, phenytoin, warfarin, digoxin, and gentamicin. These drugs require close monitoring to ensure that the blood concentration remains within the therapeutic range and does not reach toxic levels.

Melanin

Melanin is a pigment found in various parts of the body, including the skin, hair, and eyes. It is produced by specialized cells called melanocytes, which are located in the skin’s basal layer. The function of melanin in the body is not fully understood, but it is thought to play a role in protecting the skin from the harmful effects of ultraviolet (UV) radiation from the sun. Additionally, melanin may be a by-product of neurotransmitter synthesis, although this function is not well established. Overall, the role of melanin in the body is an area of ongoing research.

Antidepressants typically interfere with the natural pattern of sleep, especially by reducing REM sleep. However, Agomelatine has been found to enhance disrupted sleep-wake cycles in individuals with major depressive disorder.

Agomelatine: A New Drug for Depression Treatment

Agomelatine is a recently developed medication that is used to treat depression. Its mechanism of action involves acting as an agonist at melatonin M1 and M2 receptors, while also acting as an antagonist at 5HT2C receptors. The effects of melatonin appear to promote sleep, while the 5HT2C antagonism leads to the release of dopamine and norepinephrine in the frontal cortex. Interestingly, serotonin levels do not appear to be affected by this medication.

SNRIs are a type of antidepressant medication that work by blocking the reuptake of both serotonin and norepinephrine, providing two mechanisms to help with the antidepressant effect. They are particularly effective at inhibiting the norepinephrine transporter compared to the serotonin transporter. Examples of SNRIs include Venlafaxine, Desvenlafaxine, Duloxetine, and Milnacipran. Bupropion is a different type of antidepressant that works by inhibiting the reuptake of norepinephrine and dopamine (NDRI). Escitalopram is a selective serotonin reuptake inhibitor (SSRI), while Mirtazapine is a noradrenergic and specific serotonin antidepressant (NaSSA). Nefazodone is a serotonin antagonist/reuptake inhibitor (SARI).