Treatment Strategies (Part 1): Pharmacological Treatments

Classification and Overview of Antipsychotic Drugs

• Antipsychotic medications are considered the mainstay of pharmacological treatment for schizophrenia and related disorders.

• These drugs are categorized based on three primary criteria:     - Their chemical structure.     - The specific type of receptor binding they perform.     - Their associated adverse effects.

• Antipsychotics are divided into two main clinical groups: First Generation and Second Generation medications.

First Generation Antipsychotic Drugs (FGA)

• These medications are commonly referred to as "Typical Antipsychotics."

• Mechanism of Action: They function as full antagonists of Dopamine Type 2 ($D2$) receptors, meaning they effectively block these receptors.

• Clinical Impacts:     - They reduce positive symptoms of psychosis (such as hallucinations and delusions).     - They reduce agitation and aggression in patients.     - They provide some improvements in secondary negative symptoms (negative symptoms that arise as a result of positive symptoms or depression).

• Adverse Effects: These drugs are associated with severe adverse effects.

• Examples:     - Thorazine.     - Haldol.

Second Generation Antipsychotics (SGA)

• These medications are commonly referred to as "Atypical Antipsychotics."

• Mechanism of Action:     - They function primarily as partial agonists to stabilize $D2$ and $5HT-2A$ (Serotonin) receptors.     - They also interact with secondary receptors, including histaminergic, adrenergic, and muscarinic receptors.

• Clinical Impacts:     - They reduce positive symptoms.     - They reduce agitation and aggression.     - They reduce primary negative symptoms (the core deficits of the disorder).

• Adverse Effects: Generally associated with fewer adverse effects compared to the first generation.

• Examples:     - Risperidone.     - Olanzapine.     - Clozapine.

Dopamine Pathways and Clinical Effects

The clinical effectiveness and side profile of antipsychotics are tied to how they affect four specific dopamine pathways in the brain:

• Mesolimbic Pathway:     - Function/Problem: Hyper-dopaminergic activity in this pathway is linked to hallucinations and delusions.     - Effect of Dopamine Blockade: Leads to a reduction in positive symptoms.

• Mesocortical Pathway:     - Function/Problem: Hypo-dopaminergic activity here is linked to negative and cognitive symptoms.     - Effect of Dopamine Blockade: Can lead to an increase in negative symptoms and cognitive problems.

• Nigrostriatal Pathway:     - Function: Responsible for movement coordination.     - Effect of Dopamine Blockade: Results in adverse motor effects.

• Tuberoinfundibular Pathway:     - Function: Responsible for endocrine function.     - Effect of Dopamine Blockade: Results in adverse endocrine effects.

Receptor Occupancy and Clinical Efficacy

• The relationship between $D2$ receptor occupancy and clinical effect is threshold-dependent:     - $0\% \text{ to } 60\%$ Occupancy: No clinical effect is observed.     - $60\% \text{ to } 75\%$ Occupancy: This is the therapeutic window where the antipsychotic effect is achieved.     - Over $75\%$ Occupancy: Patients begin to experience extrapyramidal symptoms (EPS).

• Relative Efficacy (Huhn et al. 2019):     - A meta-analysis of $N = 218$ [$54\%$] studies ($n = 40,815$ [$76\%$]) showed varying Standardized Mean Differences (SMD) and $95\%$ Credibility Intervals ($CrI$) for overall symptom change.     - Top performing drugs by SMD for overall change include Amisulpride ($-0.73$), Clozapine ($-0.89$), and Olanzapine ($-0.56$).     - For positive symptoms ($N = 117$ [$29\%$], $n = 31,179$ [$58\%$]), examples include Amisulpride ($n=626$, SMD $-0.69$), Risperidone ($n=3827$, SMD $-0.55$), and Haloperidol ($n=4400$, SMD $-0.47$).

• Speed of Action: Antipsychotics work relatively quickly. Research by Agid et al. (2003) shows a significant drop in baseline scale scores within the first 1 to 4 weeks of active treatment compared to placebo.

• Comparison to General Medicine: According to Leucht et al., psychiatric drugs, including antipsychotics, tend to be more consistently effective than many drugs used for cardiovascular, pulmonary, diabetes, migraine, arthritis, and asthma conditions.

Improvements in Negative Symptoms

• 1st Generation Limitations: Most 1st generation drugs make negative symptoms worse because they are non-selective full antagonists of $D2$ receptors across all brain pathways.

• 2nd Generation Advantages: Many 2nd generation drugs improve negative symptoms through partial antagonism.

• System Stabilization: Unlike full antagonists, dopamine partial agonists stabilize the dopamine system. They provide enough activity in low-dopamine areas (like the prefrontal cortex involved in negative symptoms) while preventing excessive activation in high-dopamine areas (like the midbrain involved in positive symptoms).

Adverse Effects of Antipsychotic Medications

Adverse effects are defined as direct, unwanted effects of the drug rather than mere "side" effects.

• Extrapyramidal Symptoms (EPS): Involuntary or uncontrollable movements, tremors, and/or muscle contractions. These are sometimes called drug-induced movement disorders.

• Sedation: Intense sleepiness. Some theorists argue that sedation is the primary mechanism by which these drugs operate.

• Weight Gain: Medications (especially 2nd generation) are associated with significant weight gain, which serves as a risk factor for poor health outcomes (Correll et al., JAMA 2009).

Severe and Life-Threatening Complications

• Neuroleptic Malignant Syndrome (NMS):     - A rare side effect primarily associated with 1st Generation medications.     - Symptoms: Hyperthermia, muscular rigidity, tachycardia, fluctuations in blood pressure (hyper or hypotension), autonomic instability, confusion, and delirium.     - Rhabdomyolysis: A breakdown in muscle tissue that releases toxins into the bloodstream.     - Risk Factors: More common in the first weeks of treatment; risk increases with higher doses, multiple concurrent drugs, and in young males.     - Outcome: Can lead to loss of consciousness and death; it is frequently misdiagnosed.

• Agranulocytosis:     - Occurs in approximately $1\% \text{ to } 2\%$ of people treated with Clozapine.     - It is a life-threatening blood disorder where there is a severe drop in white blood cells.     - Symptoms: Fever, chills, increased heart rate, labored breathing, hypotension, muscle weakness, fatigue, sore throat, bleeding gums, and ulcers in the mouth and throat.     - Requirement: Patients on Clozapine require frequent blood monitoring.

Management of Adverse Effects and Adherence

• Monitoring: Critical for early detection of issues.

• Supplementary Meds: Additional medications can be used to mitigate motor issues (EPS).

• Lifestyle Interventions: Diet and exercise are recommended to combat weight gain.

• Long-Acting Injectable Antipsychotics (LAI):     - Also known as "depot" antipsychotics.     - They share the same effectiveness as oral medications but are administered via injection, typically once per month.     - Benefits: Enhances adherence, prevents rapid discontinuation, ensures stable drug concentrations over time, reduces hospitalization and poisoning risks, and allows for efficacy assessment without the variable of missed doses.

Overall Effectiveness and Relapse

• Initial Treatment:     - $80\%$ of patients improve on their first antipsychotic.     - $5\%$ improve after switching to a different antipsychotic.     - $15\%$ are considered treatment-resistant.     - Of those who are treatment-resistant, $3/4$ improve when placed on Clozapine.

• The Issue of Relapse: Relapse is very common in schizophrenia-spectrum disorders, often caused by non-adherence. Research by Rubio et al. (2020) indicates that even with LAIs, relapses occur, suggesting some patients may build tolerance over time.

• Consequences of Relapse (Nasrallah 2021):     - Brain tissue loss and treatment resistance.     - Disability, homelessness, and early mortality.     - Incarceration or criminalization.     - Suicide and PTSD.     - Hopelessness, depression, demoralization, and family burden.

Relapse Prevention Strategies

• Monitoring: Identifying early warning signs is key.

• Psychoeducation: Educating the patient about their condition and treatment.

• Support Networks: Involving the family whenever possible.

• Therapeutic Alliances: Establishing a strong therapeutic relationship between the patient and provider.