PART I: ANORGASMIA
Ranges from delayed orgasm, which is actually helpful for men experiencing premature ejaculation, but can be severe and complete in some individuals. Paxil is the worst offender among the SSRIs, Lexapro may be the least. It is caused by activation of the 5HT-2-1a receptor subtype by serotonin, so it might be reversed by adding Buspar (buspirone, an anti-anxiety medication that is a partial agonist at that receptor and competes with serotonin, but which must be taken twice a day), or Remeron (mirtazepine, a non-SSRI antidepressant that is also sedating and that increases the appetite), or cyproheptadine (an antihistamine that also helps with sleep and low appetite), both of which are complete antagonists of the receptor, blocking the activation of the receptor entirely. The efficacy of these antidotes is dose-dependent, because these agents are literally competing with serotonin for binding at the receptor that, if activated, is blocking the spinal reflex necessary to achieve orgasm.
PART II:
LOSS OF DESIRE
When a side effect, it is a purely serotonergic phenomenon that tends to be much more problematic in women than men, particularly post-menopausal women, in whom it can be complete, even without medication. When due to either low estrogen or high serotonin levels, it can be at least partially reversed by dopaminergic agents, such as Wellbutrin, and especially stimulants, such as Adderall or Ritalin. Testosterone is also an aphrodisiac, but care must be taken when exogenous steroids are prescribed. Low libido could also be a symptom of depression called anhedonia.
PART III:
ERECTILE DYSFUNCTION (ED)
Caused by microvascular and/or neurologic damage in middle-age, after years of poorly-controlled hypertension, diabetes, and hypercholesterolemia (atherosclerosis) to name the most common culprits, and is also usually complete following radical prostatectomy for cancer due to damage that occurs to the pudendal nerve plexus. When ED is due to medication, it is either a sympathomimetic norepinephrine-enhancing drug, such as stimulants used to treat ADD, and recreational substances (especially cocaine), which activate the fight-or-flight response and dampen the parasympathetic nervous system, necessary for erectile function, or serotonin-enhancing medications that most likely cause this problem indirectly, by diminishing sexual desire. Treatment is to modulate or discontinue the offending agent, or adding a medication like Viagra or Cialis.
