Neurotransmitters – chemicals that are responsible for transmitting signals from nerve cell to nerve cell within the brain.
Serotonin, norepinephrine, and dopamine are released from one cell, cross the synaptic cleft between cells, and connect with receptors on the membranes of adjacent cells to create signal conduction.
Reuptake – the process where neurotransmitters are either taken back up into the presynaptic nerve cell or broken down.
Monoamine oxidase is an enzyme that breaks down neurotransmitters in neurons.
Disorders affecting mood and mental function are related to deficiency or dysfunction of neurotransmitters.
Depression is related to deficiency or dysfunction of neurotransmitters serotonin and norepinephrine; dopamine is involved in psychosis, including schizophrenia.
Drug therapy is intended to manipulate levels of neurotransmitters by mimicking actions or altering the processes that eliminate them from the synaptic cleft.
Depression can be caused by external (exogenous) or internal (endogenous) sources.
Treatment accounts for several of the top prescription medications in the U.S.
Endogenous depression is more likely to require drug therapy for control.
Norepinephrine, serotonin, and probably dopamine are neurotransmitters involved in mood.
ANTIDEPRESSANTS-
• Selective serotonin reuptake inhibitors (SSRIs)
• Serotonin-norepinephrine reuptake inhibitors (SNRIs)
• Tricyclic antidepressants (TCAs)
• Monoamine oxidase inhibitors (MAOIs)
• Bupropion (Wellbutrin)
• Trazodone (Desyrel)
3-6 weeks for patients to feel the effects of antidepressants; therapy trial should last 3-4 weeks; doses should be changed only once a month.
Antidepressants should not be stopped immediately; worsening symptoms may be experienced if an antidepressant dose is not gradually decreased.
SSRIs and SNRIs are first-line therapy for depression.
SSRIs block serotonin reuptake into the presynaptic cleft; used for obsessive-compulsive disorder (OCD) – a form of anxiety where obsessive thoughts intrude daily consciousness and impair function – and premenstrual dysphoric disorder (PMDD) – emotional and behavioral changes in the second half of a woman’s menstrual cycle, similar to PMS but PMDD is much more severe and life altering. SSRIs may also be used for anxiety and panic disorder. SNRIs block reuptake of both serotonin and norepinephrine.
Duloxetine (Cymbalta) is primarily used for pain associated with depression.
Common SSRI side effects include nausea, vomiting, dry mouth, drowsiness, insomnia, headache, and diarrhea. Some patients experience sexual dysfunction. Side effects can subside over time. Effects are frequent reasons why patients stop taking these medications. Fluoxetine (Prozac) can cause weight loss and is sometimes used for eating disorders; this however should not be used simply as a weight loss agent.
Antidepressants (SSRIs) have been associated with an increased risk of suicidal thoughts and tendencies, especially in pediatric and adolescent patients. Patients should be monitored closely and should be offered counseling and psychotherapy in addition to medication.
Patients taking SSRIs are at risk for serotonin syndrome, a potentially fatal medication condition when too much serotonin is present, causing changes in cardiovascular function and even heart attack.
Patients taking more than one antidepressant or St. John’s Wort – a herbal product taken for depression – are at a particularly high risk for serotonin syndrome.
Patients experiencing a combination of racing heart rate, fever, high blood pressure, and headache, may be experiencing signs of serotonin syndrome, should seek medical attention immediately.
Tricyclic antidepressants get their name from their chemical structure, which contains three rings.
TCAs block reuptake of norepinephrine and/or serotonin.
Sometimes prescribed for insomnia because the primary side effect is drowsiness; can be used for patients whose depression symptoms include insomnia. It is used to treat some neuropathic pain and select nerve conditions.
Also included in this drug class is a tetracycline agent; with a fourth ring on its chemical structure; similar drug activity and properties. Before SSRIs, TCAs were the most widely prescribed class of antidepressants.
MAOIs are not used as much as they use to, they are saved as a last resort for intractable depression symptoms. Newer/other drug therapies have fewer side effects and drug interactions.
MAOIs work by inhibiting one of the primary enzymes that metabolizes neurotransmitters, allowing neurotransmitter levels to rise in the synaptic cleft.
Side effects include heart palpitations and postural hypotension, dizziness, headache, tremors, insomnia, anxiety, restlessness, agitation, and anticholinergic effects (dry mouth, blurred vision, constipation, urinary retention).
MAOIs interact with numerous other drugs, both prescription and OTC.
MAOIs interact with tyramine, a substance found in pickled and aged foods (aged cheese, beer, wine, sauerkraut, and pickled foods); the interaction causes serotonin syndrome.
0 Comments