Human colonization begins within the gastrointestinal tract, with subsequent spread to moist cutaneous sites such as the perineum and axilla.
It forms smooth fluorescent green colonies at 42o C, with a characteristic sweet (grape-like) odor, making it easy to recognize on solid media in the laboratory.
It is associated with nosocomial infections, often severe and life-threatening, especially in immunocompromised hosts.
Chronic infection leads to progressive lung disease in cystic fibrosis, frequently complicated by antimicrobial resistance.
Drugs can induce or inhibit individual enzymes; such information is generally readily available in the Physicians' Desk Reference or other medication guides.51–54 Although it is tempting to use gabapentin and citalopram solely because of their "clean" metabolic profiles (they have no effect on hepatic enzyme systems),54 they are not free of either risks or side effects.44,54,55 When an AED is added to an antidepressant, induction of hepatic enzymes may decrease the antidepressant's effectiveness.56 Sedating antidepressants may trigger seizures in patients whose seizure threshold is lowered by drowsiness.42 Because most drug interactions are predictable, they can usually be anticipated, especially with chronic use.
The choice of antidepressant medication should be based on the individual's needs rather than the fear of drug interactions or the small risk of a seizure.
Treatment should include alkalinization to avoid malignant arrhythmias,4 but seizures in such circumstances may be prolonged or recurrent, despite appropriate use of AEDs.8 At San Francisco's poison control center, overdoses of imipramine and amitriptyline accounted for 29% of the patients who had seizures.5 Massive overdoses of newer antidepressant drugs, such as fluvoxamine in doses above 1500 mg, have also been associated with seizures.45 Seizures are a neurotoxic effect of lithium and can occur even with plasma concentrations within the usual therapeutic range.
EEG abnormalities are predictive of seizures.48 The risk of seizures is increased in elderly people, probably owing to age-related reduction in metabolism and clearance that leads to drug accumulation, despite dosages well tolerated in younger patients.7 Toxic amounts of antidepressant drugs also can accumulate in younger people.
In patients with epilepsy who require ECT, maintenance AEDs should be withheld the day of treatment to obtain the best response.44 Newer technologies for treating depression, such as transcranial magnetic stimulation and vagus nerve stimulation (VNS), have not been associated with any increased risk of seizures.59 Adapted from: Koppel BS. Because depression is common in the general population and occurs even more often in patients with epilepsy (up to 50%, depending on the screening tool used39), and because treatment of depression usually requires long-term drug treatment, the choice of antidepressant medication must be made carefully, taking into account the possible effect on seizure threshold.The choice of antidepressant medication should be based on the needs of the individual patient, however, not the small risk of a seizure or fear of drug interactions.The active drug concentration actually within the brain is a product of many overlapping factors: A newly emphasized property of drugs is chirality: the beneficial or toxic effects of a drug depend on its chemical "handedness." The racemic (L or D) form of a drug affects its metabolism and reuptake, which, in turn, results in variable effects on antidepressant efficacy and on seizure propensity.49 Enzyme-inhibiting antidepressant drugs, such as the SSRIs and TCAs, may require downward adjustment in the dosage of concurrently administered AEDs that are also metabolized by the cytochrome P-450 (CYP450) microsomal system in the liver.In other cases, phenytoin and carbamazepine inhibit the metabolism of antidepressant drugs, like fluoxetine or the TCAs, which leads to unintended toxicity from the antidepressant.40,41 Reference to drug interaction charts is necessary to anticipate the effects of one drug on another, as there are several isoenzymes of both the CYP450 and GT systems.