12.2 Psychopharmacology of mood disorders

Mood disorders can wreak havoc on our lives. Luckily, there are meds that can help. From SSRIs to mood stabilizers, these drugs work on our brain chemistry to lift our spirits and level out our moods.

But it's not all sunshine and roses. These meds can have some nasty side effects. It's a balancing act between feeling better and dealing with dry mouth or weight gain. Finding the right med and dose takes time and patience.

Antidepressant Medications

Types of Antidepressants and Their Mechanisms

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• Antidepressants alleviate symptoms of depression by modulating neurotransmitter levels in the brain
• Selective serotonin reuptake inhibitors (SSRIs) block the reuptake of serotonin in the synaptic cleft
  • Increases availability of serotonin for neurotransmission
  • Commonly prescribed SSRIs include fluoxetine (Prozac) and sertraline (Zoloft)
• Tricyclic antidepressants inhibit the reuptake of both serotonin and norepinephrine
  • Affect multiple neurotransmitter systems simultaneously
  • Examples include amitriptyline and imipramine
• Monoamine oxidase inhibitors (MAOIs) prevent the breakdown of monoamine neurotransmitters
  • Increase levels of serotonin, norepinephrine, and dopamine
  • Less commonly prescribed due to potential food interactions
  • Examples include phenelzine and tranylcypromine

Efficacy and Side Effects of Antidepressants

• SSRIs generally have fewer side effects compared to older antidepressants
  • Common side effects include nausea, sexual dysfunction, and sleep disturbances
• Tricyclic antidepressants can cause anticholinergic effects
  • Dry mouth, blurred vision, and constipation are frequent side effects
• MAOIs require dietary restrictions to avoid potentially dangerous interactions
  • Foods high in tyramine (aged cheeses, cured meats) can cause hypertensive crisis
• Antidepressants typically take 2-4 weeks to show therapeutic effects
  • Patients may experience side effects before noticing mood improvements
• Risk of increased suicidal thoughts in young adults during initial treatment phase
  • Requires close monitoring and follow-up with healthcare providers

Other Psychotropic Medications

Mood Stabilizers and Their Applications

• Mood stabilizers treat bipolar disorder and prevent manic and depressive episodes
• Lithium serves as the gold standard mood stabilizer
  • Effective in treating both manic and depressive phases of bipolar disorder
  • Requires regular blood level monitoring due to narrow therapeutic window
  • Side effects include tremor, weight gain, and potential thyroid dysfunction
• Anticonvulsants often used as mood stabilizers
  • Valproic acid and carbamazepine show efficacy in bipolar disorder treatment
  • Mechanism of action involves modulation of GABA neurotransmission

Antipsychotic Medications and Their Uses

• Antipsychotics primarily treat schizophrenia and other psychotic disorders
• First-generation (typical) antipsychotics primarily block dopamine D2 receptors
  • Effective in reducing positive symptoms of schizophrenia (hallucinations, delusions)
  • Examples include haloperidol and chlorpromazine
• Second-generation (atypical) antipsychotics affect multiple neurotransmitter systems
  • Target both dopamine and serotonin receptors
  • May improve negative symptoms and cognitive deficits in schizophrenia
  • Examples include risperidone and olanzapine
• Antipsychotics also used as adjunct treatments in bipolar disorder and major depression
  • Can help stabilize mood and augment antidepressant effects

Pharmacological Considerations

Neurotransmitter Systems and Drug Targets

• Serotonin system plays a crucial role in mood regulation and emotional processing
  • SSRIs and some antipsychotics target serotonin receptors and transporters
• Dopamine system involved in motivation, reward, and psychotic symptoms
  • Antipsychotics primarily modulate dopamine neurotransmission
• Norepinephrine system affects arousal, attention, and stress response
  • Some antidepressants target norepinephrine reuptake or breakdown
• GABA system provides inhibitory neurotransmission
  • Mood stabilizers and some antidepressants influence GABA function

Therapeutic Window and Dosing Considerations

• Therapeutic window represents the range between minimum effective dose and toxic dose
• Lithium has a narrow therapeutic window
  • Requires careful dosing and regular blood level monitoring
  • Therapeutic range typically between 0.6-1.2 mEq/L
• Antidepressants often require dose titration to achieve optimal effects
  • Starting at lower doses and gradually increasing reduces side effect burden
• Antipsychotic dosing based on receptor occupancy theory
  • Optimal D2 receptor occupancy around 65-80% for therapeutic effects
  • Higher occupancy increases risk of extrapyramidal side effects

Side Effects and Management Strategies

• Common side effects of psychotropic medications affect quality of life
  • Weight gain associated with many antipsychotics and mood stabilizers
  • Sexual dysfunction frequently reported with SSRIs
• Strategies to manage side effects include:
  • Dose adjustments to find optimal balance between efficacy and tolerability
  • Switching to medications with different side effect profiles
  • Adjunctive treatments to counteract specific side effects (metformin for weight gain)
• Long-term side effects require ongoing monitoring
  • Metabolic syndrome risk with atypical antipsychotics
  • Potential for tardive dyskinesia with long-term antipsychotic use
• Discontinuation syndromes can occur with abrupt cessation of many psychotropic medications
  • Gradual tapering recommended to minimize withdrawal symptoms