Gastrointestinal effects, antidepressant drugs

Citalopram is a selective serotonin re-uptoke inhibitor (SSRI). These tend to have fewer ontimuscarinic effects than tricyclic antidepressant (TCA) drugs, such as dry mouth and constipation however, SSRIs tend to cause gastrointestinal effects, such as nausea and vomiting. MAOIs are monoamine oxidase inhibitors. 

Beta-adrenoceptor antagonists, particularly propranolol, have been shown to be effective for anxiety symptoms particularly in situational anxiety and GAD. Buspirone, an azaspirodecanedione, is an agonist at 5-HTlA receptors and seems to have anxiolytic effects, though it is less potent than the BDZs and the effects take up to three weeks to become evident. There is high first pass metabolism and a considerable proportion of the effect is due to a metabolite (1-PP). The principal adverse effects of buspirone are nausea, gastrointestinal upset and headache. Antidepressant drugs, both the older tricyclic antidepressants and the newer drugs, have been demonstrated to have anxiolytic effects in mixed anxiety-depressive patients, GAD and panic disorder. 

Two reviews have systematically addressed the safety of St. John s wort. One showed that the most common adverse events were gastrointestinal symptoms, dizziness, confusion, tiredness, sedation, and dry mouth (3). A second review compared the adverse effect profile of St. John s wort with those of conventional antidepressants (4). The adverse effects of St. John s wort were fewer and less serious than those associated with conventional antidepressant drugs. 

Principal side effects are gastrointestinal and central nervous system symptoms, including drowsiness, dizziness, and diarrhea. Zolpidem may increase the depressant effects of other sedative drugs, such as the an-tipsychotics, tricyclic antidepressants, and antihistamines. 

In addition, there are several drugs that are related to the antipsychotics that may also be prescribed to youths for other conditions. These include the antidepressant amoxapine and the preanesthetic droperidol. Metoclopramide and prochlorperazine are related agents that are marketed for their effects on the gastrointestinal system. 

Buspirone causes less psychomotor impairment than benzodiazepines and does not affect driving skills. The drug does not potentiate effects of conventional sedative-hypnotic drugs, ethanol, or tricyclic antidepressants, and elderly patients do not appear to be more sensitive to its actions. Nonspecific chest pain, tachycardia, palpitations, dizziness, nervousness, tinnitus, gastrointestinal distress, and paresthesias and a dose-dependent pupillary constriction may occur. Blood pressure may be significantly elevated in patients receiving MAO inhibitors. 

The anticholinergic effects of imipramine and other tricyclic antidepressants can delay gastrointestinal motility enough to interfere with the absorption of various other drugs. Such was the case in an experimental study of the absorption of levodopa in four healthy subjects (177). It is likely that this effect may interfere with absorption of other drugs, especially those, such as chlorpromazine, that are extensively metabolized in the gut. 

Whether elderly patients taking lithium received proper monitoring was questioned in a case note audit of 91 patients, over 40% of whom had deviations from practice standards. These included absence of pretreatment laboratory tests, infrequent monitoring of serum lithium concentrations, lack of adequate adverse effects documentation, and the use of risky concomitant drugs (403). In a placebo-controlled study, there was poor tolerance of hthium augmentation of antidepressants in 76% (13/17) of elderly (mean age 70 years) patients at a mean serum concentration of 0.63 mmol/1, due to tremor and muscle twitches, cognitive disturbance, tiredness and sedation, and gastrointestinal upsets (404). 

Adverse Effects. Typical antidepressant doses of SSRIs can cause side effects of insomnia, jitteriness, restlessness, and agitation, and lead to drug discontinuation in patients with panic disorder. Transient gastrointestinal disturbances occur more frequently with SSRIs than with TCAs. Thus low initial SSRI doses should be prescribed. Sleep disturbances, headaches, and sexual dysfunction often are problematic. ... 

Figure 4.1 Second generation antidepressants, some of which are listed here, have the fewest side effects of drugs for depression treatment. Except for Amoxapine and Venlafaxine, the incidence of sexual dysfunction is very low, compared to the high probability of sexual dysfunction occurring with TCAs and SSRIs (see Figures 2.1 and 3.2). However, unlike TCAs and SSRIs, gastrointestinal upset can occur more frequently with second generation antidepressants.

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