SNRIs Flashcards
SNRI mode of action?
SNRIs work by inhibiting the reuptake of serotonin and norepinephrine in the brain, which increases the concentration of these neurotransmitters in the synaptic cleft and enhances neurotransmission.
SNRIs indications?
Depression: Effective in treating major depressive disorder by improving mood, energy levels, and feelings of well-being.
Anxiety: Used to treat generalized anxiety disorder, panic disorder, and social anxiety disorder.
Chronic Pain: Particularly effective in treating pain syndromes, including neuropathic pain and fibromyalgia.
What are some common examples of SNRIs?
venlafaxine (Effexor)
duloxetine (Cymbalta),
Desvenlafaxine (Pristiq).
What are the side effects of SNRIs?
Nausea: SNRIs increase serotonin levels in the gastrointestinal tract as well as in the brain, which can stimulate the gut’s serotonin receptors and trigger nausea.
Increased Blood Pressure and Heart Rate: The increase in norepinephrine levels can lead to vasoconstriction and an increase in heart rate and blood pressure, as norepinephrine is a key neurotransmitter in the sympathetic nervous system, which controls the body’s fight-or-flight responses.
Dizziness And Headache: These can occur as a result of changes in neurotransmitter levels affecting the central nervous system. Dizziness especially may also be related to blood pressure changes.
Sexual Dysfunction: Increased serotonin levels can inhibit sexual behavior by affecting receptors in the brain that are involved in sexual arousal and pleasure.
Dry Mouth SNRIs can affect the autonomic nervous system, which controls various unconscious functions, including saliva production, leading to decreased secretion.
Insomnia and Sleep Disturbances: The increase in both serotonin and norepinephrine can affect sleep patterns. Norepinephrine in particular plays a role in wakefulness and can therefore disrupt sleep.
Increased Sweating: This side effect is likely linked to the drug’s impact on the autonomic nervous system, particularly through norepinephrine’s effects on body temperature regulation.
Constipation: Physiological Rationale: Increased serotonin levels in the gastrointestinal tract can affect motility and fluid secretion, reducing bowel movement frequency.
Weight Changes: Changes in appetite and metabolism due to altered neurotransmitter levels can lead to weight gain or loss, though this is more often associated with other classes of antidepressants.
Fatigue: While norepinephrine generally stimulates the body, the initial adjustments to neurotransmitter changes or the body’s response to other side effects like poor sleep can result in fatigue.
What are some potential drug interactions with SNRIs?
Selective Serotonin Reuptake Inhibitors (SSRIs) and Other Antidepressants
Taking SNRIs with SSRIs or other antidepressants, especially those that affect serotonin levels (like tricyclic antidepressants or monoamine oxidase inhibitors [MAOIs]), can increase the risk of serotonin syndrome. This is a potentially life-threatening condition characterized by high body temperature, agitation, increased reflexes, tremor, sweating, dilated pupils, and diarrhea.
Monoamine Oxidase Inhibitors (MAOIs)
Concomitant use with MAOIs can lead to severe serotonin syndrome. Due to this risk, there should be a washout period of at least 14 days between discontinuing an MAOI and starting an SNRI, or vice versa.
Antiplatelet Agents and Anticoagulants
SNRIs can increase the risk of bleeding by affecting platelet function and enhancing the effects of anticoagulants and antiplatelet drugs.
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): Concurrent use with NSAIDs can also increase the risk of gastrointestinal or other bleeding, as both can impair platelet function.
Central Nervous System (CNS) Depressants: SNRIs may enhance the effects of other CNS depressants, leading to increased sedation and decreased cognitive function.
St. John’s Wort: This herbal supplement can induce hepatic enzymes and potentially reduce the efficacy of SNRIs by increasing their metabolism. It may also contribute to the risk of serotonin syndrome when used with SNRIs.
Sympathomimetic Agents: Drugs that mimic the effects of the sympathetic nervous system (e.g., some cold medications and decongestants) may have their effects intensified by SNRIs, potentially leading to increased heart rate and blood pressure.
Nursing considerations for SNRIs?
Monitoring: Nurses should monitor blood pressure and heart rate, as SNRIs can increase both.
Education: Educating patients about the importance of adherence, potential side effects, and the need to avoid sudden discontinuation of the medication.
Assessment: Regularly assessing the patient’s pain levels, mood, and overall response to therapy.
Suicide Risk: Especially in children, adolescents, and young adults, monitoring for worsening depression or suicidal thoughts is crucial.
Pregnancy: Discussing potential risks and benefits with patients who are pregnant or planning to become pregnant, as SNRIs can have effects on the fetus and newborn, such as withdrawal symptoms and respiratory issues.
SNRIs vs SSRIs why use one vs the other?
SNRIs
Advantages:
Dual Action: SNRIs increase the levels of both serotonin and norepinephrine, which can make them effective for a broader range of symptoms compared to SSRIs. This dual action can be particularly beneficial in treating depression accompanied by chronic pain (e.g., Duloxetine is FDA approved for treating diabetic neuropathy, fibromyalgia, and chronic musculoskeletal pain).
Effective for Severe Depression: Some studies suggest that SNRIs may be more effective in treating severe depression than SSRIs.
Reduced Sexual Side Effects: While still present, some patients might experience fewer sexual side effects with SNRIs compared to SSRIs.
Disadvantages:
More Pronounced Physical Side Effects: SNRIs can cause increased blood pressure and heart rate, which can be a concern in patients with cardiovascular issues.
Withdrawal Symptoms: Like SSRIs, SNRIs can lead to withdrawal symptoms, but these may be more intense due to the involvement of norepinephrine, necessitating a careful tapering process.
Cost: Some SNRIs are newer and may be more expensive than older SSRIs.
SSRIs
Advantages:
Good Tolerability: Generally, SSRIs have a favorable side effect profile, making them a first-line treatment for depression and anxiety.
Safety in Overdose: SSRIs are relatively safe in overdose, making them preferable in patients at risk for suicide.
Efficacy for a Range of Disorders: They are effective in treating a variety of disorders, including depression, a range of anxiety disorders, OCD, and PTSD.
Disadvantages:
Sexual Dysfunction: This is a significant issue with SSRIs and can affect compliance and quality of life.
Emotional Blunting: Patients may experience emotional numbing or reduced emotional responsiveness, which can be distressing.
Gastrointestinal Side Effects: Common issues include nausea, diarrhea, and other gastrointestinal disturbances, particularly when treatment is initiated.
Summary
The choice between an SNRI and an SSRI often depends on the specific symptoms and medical history of the patient. SNRIs may be chosen for their effectiveness in treating severe depression or depression with associated physical pain. SSRIs might be preferred for their safety profile, particularly in patients who are at risk of overdose, and their efficacy across a broad range of depressive and anxiety disorders.
Ultimately, the decision on which class of medication to use will depend on the individual patient’s health profile, their response to previous medications, and specific treatment goals. Both SSRIs and SNRIs require careful monitoring for side effects and potentially adjusting the dose to manage or mitigate side effects effectively.
SNRIs vs Tricyclic antidepressents why use one over another?
SNRIs
Advantages:
Side Effect Profile: Generally, SNRIs have a more favorable side effect profile compared to TCAs. They are less likely to cause anticholinergic effects (such as dry mouth, constipation, urinary retention), which are common with TCAs.
Safety in Overdose: SNRIs are safer in overdose than TCAs, making them a better option for patients at risk of suicide.
Dual Action: By increasing both serotonin and norepinephrine, SNRIs can be effective in treating a broad range of depressive symptoms and are particularly useful in patients with significant fatigue or pain syndromes.
Disadvantages:
Withdrawal Symptoms: Patients discontinuing SNRIs may experience significant withdrawal symptoms unless the medication is carefully tapered.
Cost: SNRIs are generally newer than TCAs and may be more expensive.
TCAs
Advantages:
Cost: TCAs are typically less expensive than newer antidepressants, which can be an important consideration in long-term treatment.
Broad Efficacy: TCAs have been proven effective in a wide range of depressive symptoms and are particularly useful in patients with sleep disturbances due to their sedative effects.
Chronic Pain: TCAs are often used to treat neuropathic pain and may be more effective in certain types of pain than SNRIs.
Disadvantages:
Side Effects: TCAs have a higher incidence of anticholinergic side effects, which can be particularly problematic in elderly patients or those with certain medical conditions.
Cardiac Effects: TCAs can be cardiotoxic, especially in overdose, and are generally avoided in patients with known heart conditions.
Drug Interactions: TCAs interact with a wide range of medications and require careful monitoring when used with other drugs.
Choosing Between SNRIs and TCAs
Patient’s Medical History: TCAs are usually not preferred for elderly patients or those with heart conditions, glaucoma, or urinary retention due to their side effects. SNRIs might be chosen for these patients.
Symptom Profile: For a patient with significant fatigue or pain, an SNRI might be more beneficial. For issues like insomnia or neuropathic pain, a TCA might be more effective.
Risk of Suicide: Given their toxicity in overdose, TCAs are typically avoided in patients at high risk for suicide.
Patient Tolerance: Individual tolerance to side effects can also guide the choice. Some patients may tolerate one class of medication better than the other.
Ultimately, the choice between an SNRI and a TCA will depend on a careful assessment of the patient’s specific symptoms, medical history, and risk factors, as well as their previous responses to medications, if available. Regular monitoring and adjustment may be necessary to find the most effective and safe medication for a given individual.
SNRIs vs MAOIs
SNRIs
Advantages:
Broader Use: SNRIs are commonly prescribed for depression, anxiety, and certain chronic pain conditions. They are considered first or second-line treatments for these conditions.
Side Effect Profile: Generally, SNRIs have a more manageable side effect profile compared to MAOIs. They are less likely to cause severe dietary and drug interaction issues.
Safety: SNRIs are safer in overdose compared to MAOIs and many other antidepressants.
Disadvantages:
Withdrawal Symptoms: Patients discontinuing SNRIs may experience significant withdrawal symptoms unless the medication is carefully tapered.
Blood Pressure: SNRIs can increase blood pressure, requiring monitoring in patients with hypertension.
MAOIs (Phenelzine + Tranylcypromine)
Advantages:
Effectiveness in Treatment-Resistant Cases: MAOIs can be very effective, particularly in cases of treatment-resistant depression. They may also be beneficial for patients with atypical depression.
Broad Impact on Neurotransmitters: MAOIs increase levels of several neurotransmitters (not just serotonin and norepinephrine, but also dopamine), which can be advantageous depending on the patient’s symptom profile.
Disadvantages:
Dietary Restrictions: MAOIs can interact with tyramine-rich foods like aged cheeses and cured meats, leading to dangerous increases in blood pressure. Patients need to follow strict dietary restrictions.
Drug Interactions: MAOIs can cause severe interactions with various other medications, including over-the-counter products like certain decongestants and other antidepressants. These interactions can lead to serotonin syndrome, a potentially life-threatening condition.
Side Effects: They can have more significant side effects, including orthostatic hypotension, weight gain, and sexual dysfunction.
Choosing Between SNRIs and MAOIs
Clinical Considerations: SNRIs are typically preferred due to their ease of use, safety profile, and fewer dietary and drug interaction concerns. They are commonly prescribed as first-line treatments.
Patient History and Treatment Response: MAOIs might be considered for patients who have not responded to other treatments, especially if they exhibit atypical symptoms like increased sleep and appetite, and mood reactivity.
Safety and Monitoring Needs: The need for dietary restrictions and potential for severe interactions makes MAOIs less desirable for patients who may not adhere strictly to dietary guidelines or who are on multiple medications.
In summary, while SNRIs are generally preferred for their safety and ease of use, MAOIs remain a valuable option for specific cases where other treatments have failed. The choice between these medications should be guided by a thorough evaluation of the patient’s medical history, symptomatology, and treatment response history. Regular follow-ups and patient education are crucial, especially when prescribing MAOIs, due to their complex management requirements.
SNRIs vs Mirtazapine?
Advantages:
Broader Impact on Neurotransmitters: SNRIs increase both serotonin and norepinephrine, which can be beneficial in treating a wide range of depressive symptoms as well as anxiety disorders and chronic pain conditions.
Flexibility in Treatment: They are often used in various psychiatric and neurological conditions, providing a broad therapeutic range.
Disadvantages:
Side Effects: Common side effects include nausea, headache, dry mouth, dizziness, and sexual dysfunction. SNRIs can also increase blood pressure, requiring monitoring in patients with hypertension.
Withdrawal Symptoms: Discontinuation of SNRIs needs to be gradual to avoid withdrawal symptoms, which can be severe.
Mirtazapine
Mechanism: Mirtazapine works by antagonizing central α2-adrenergic auto and hetero-receptors (increasing the release of norepinephrine and serotonin), and blocking specific serotonin receptors to enhance mood and effects on neurotransmission. It also blocks histamine receptors, contributing to its sedative effects.
Advantages:
Effective for Sleep and Appetite: Mirtazapine is often chosen for patients suffering from insomnia or poor appetite, as it can increase appetite and promote weight gain, and its sedative effects can be beneficial for sleep.
Low Sexual Dysfunction Risk: Unlike many other antidepressants, mirtazapine generally does not cause sexual dysfunction.
Rapid Onset of Action: Some effects, particularly improvements in sleep, may be noticed quickly after starting the medication.
Disadvantages:
Weight Gain and Sedation: While beneficial for some, the increased appetite and sedation can be problematic for others, especially those at risk for obesity or who perform tasks that require alertness.
Less Effective for Anxiety: Mirtazapine is generally not the first choice for anxiety disorders, as its anxiolytic effects are less pronounced than those of SNRIs.
Choosing Between SNRIs and Mirtazapine
Symptom Profile: If a patient struggles with insomnia, significant weight loss, and depression, mirtazapine might be advantageous. For those dealing with depression accompanied by chronic pain or significant anxiety, SNRIs might be more appropriate.
Side Effects Consideration: For patients where potential sexual dysfunction or withdrawal symptoms are a concern, mirtazapine might be preferable.
Medical History: In patients with a history of high blood pressure or heart issues, mirtazapine might be chosen over an SNRI due to its negligible impact on blood pressure.
In practice, the decision to use an SNRI versus mirtazapine will depend on a balanced consideration of these factors. Sometimes, if a patient’s depression is not adequately managed by one, the other might be added or substituted to achieve better results, considering the unique action mechanisms of each.
