Fluoxetine toxicity

The symptoms may have been due to a direct effect of clarithromycin or else inhibition of hepatic cytochrome P450 metabolism, leading to fluoxetine toxicity. Clarithromycin occasionally causes hallucinations. 

Phenytoin Phenytoin serum levels can be increased in some patients by fluoxetine. Toxicity may occur. There are also isolated reports of phenytoin toxicity with the concurrent use of fluvoxamine and paroxetine. Phenyltoin and sertraline do not normally interact nevertheless, two patients have shown increased serum phenytoin levels. 

An isolated case report describes apparent acute fluoxetine toxicity in a man brought about by the use of clarithromycin. Another isolated report describes the development of what is thought to be the serotonin syndrome in a 12-year-old boy taking sertraline and erythromycin. 

The authors attribute what was seen to fluoxetine toxicity in the first case, and to the serotonin syndrome in the second case. They postulated that erythromycin (a known and potent inhibitor of cytochrome P450 isoenzyme CYP3A4) and the related macrolide clarithromycin, reduced the metabolism of the SSRIs, thereby raising their serum levels and precipitating the observed toxicity. ... 

The effects of buspirone are decreased when the drug is administered with fluoxetine Increased serum levels of buspirone occur if the drug is taken with erythromycin or itraconazole Should any of these combinations be required, the dosage of buspirone is decreased to 2.5 mg BID, and the patient is monitored closely. Venlafaxine blood levels increase with a risk of toxicity when administered witii MAOIs or cimetidine There is an increased risk of toxicity when trazodone is administered with the phenothiazines and decreased effectiveness of trazodone when it is administered with carbamazepine Increased serum digoxin levels have occurred when digoxin is administered with trazodone There is a risk for increased phenytoin levels when phenytoin is administered witii trazodone... 

Certain medications (e.g., cimetidine, diltiazem, erythromycin, fluoxetine, fluvoxamine, isoniazid, itraconazole, ketoconazole, nefazodone, propoxyphene, and verapamil) added to carbamazepine therapy may cause carbamazepine toxicity. 

Increased plasma concentrations of TCAs and symptoms of toxicity may occur when fluoxetine and paroxetine are added to a TCA regimen. 

Decreased cigarette consumption in smokers, easier to stop smoking Exaggerated response to warfarin and phenytoin Increased efficacy of omeprazole, increased toxicity of mephenytoin Absence of codeine efficacy, no effect of encainide, increased levels of tricyclic antidepressants, fluoxetine, phenothiazines Sustained paralysis to succinylcholine, possible increased toxicity of cocaine Unknown... 

Additional ADRs linked to diet pills include psychosis myocardial ischemia drug interactions, such as the interaction of fenfluramine with imipramine, fenfluramine with amitriptyline or desipramine, or the toxic reaction between fluoxetine and phentermine and the release of serotonin while inhibiting its reuptake, contributing to hyperserotonin reactions. When the next craze takes hold of patients and their physicians, hopefully physicians and pharmacists will take a more vocal position and recommend restraint, xmtil some proof of efficacy and lack of toxicity is shown for new faddish off-label combinations. 

Bostwick, J.M. and Brown, T.M., A toxic reaction from combining fluoxetine and phentermine, /. Clin. PsychopharmacoL, 16,189-190,1996. 

Other Antidepressants. Antidepressant refinements for the next 30 years primarily consisted of the development of new TCAs. However, in 1988, a novel antidepressant class, the selective serotonin reuptake inhibitors (SSRIs), was introduced in the United States. The chief innovation of the SSRIs was that they afforded the comparable effectiveness of the TCAs with fewer side effects and minimal toxicity. The debut of the SSRIs coincided with the reworking of the nosology of the anxiety disorders in DSM-III and DSM-IV. As a result, the SSRIs have been studied extensively in each of the respective anxiety disorders and in many cases have obtained FDA approval for the treatment of one or more of these anxiety syndromes. The SSRIs currently available in the United States include citalopram (Celexa), escitalo-pram (Lexapro), fluoxetine (Prozac), fluvoxamine (Luvox), paroxetine (Paxil), and sertraline (Zoloft). 

Specific Serotonin Reuptake inhibitors (SSRis). To date, the only SSRI studied in AN is fluoxetine (Prozac). During the acute refeeding phase of treatment, fluoxetine shows modest improvement in weight gain while a larger controlled study during the maintenance phase of treatment demonstrated effectiveness in the prevention of relapse. From the standpoint of side effects and toxicity, the SSRIs are clearly... 

Although studies suggest that antidepressants of any class are efficacious for the treatment of BN, the favorable side effect profile and lower toxicity of the newer generation antidepressants make their use preferable. Of these, fluoxetine is the best studied and is the only antidepressant at this time with FDA approval for the treatment of BN. 

For highly potent APIs, profound effects can occur at low ng levels, the adverse effect of ethynylestradiol on fish populations is one example [107]. Another example is the development of resistant bacterial strains induced by the release of antibiotics into the environment [112, 113]. Dome et al. [114] concluded that fluoxetine, ibuprofen, diclofenac, propranolol and metoprolol exhibit relatively high acute toxicity to aquatic species. In addition, due to the inherent properties of these chemicals, pharmacodynamic effects were observed in the heart rate of Daphnia magna for the (3-blockers propranolol and metoprolol. 

Sumatriptan is a 5HT (serotonin) agonist indicated in the treatment of migraine. Sumatriptan causes vasoconstriction and must therefore be used with caution in patients with coronary heart disease, such as angina. Concurrent administration of the agonist, sumatriptan and antagonists, such as fluoxetine, which is a selective serotonin re-uptake inhibitor, leads to increased CNS toxicity. 

SSRIs—fluvoxamine, fluoxetine, and paroxetine, more than sertraline and citalopram Inhibition of metabolism at CYP2D6 isoenzyme TCA toxicity due to up to 10-fold increase in TCA levels with coadministration Lower TCA dose Baumann, 1996... 

All SSRIs (e.g., Feonard et ah, 1997) and in particular fluoxetine, Fluvosamine and paroxetine are metabolized by hepatic cytochrome P450 enzymes. Therefore, it is important to be aware of the possibility that the therapeutic or toxic effects of other medications metabolized by the cytochrome P450 isoenzyme system can be increased. Substantial inhibition of these isoenzymes converts a normal metabolizer into a slow metabolizer with regard to this specific pathway. Inhibition of the hepatic oxidative isoenzymes has been associated with a reduction, to a varying extent, in the clearance of many therapeutic agents, including the TCAs, several neuroleptics, antiarrhythmics, theophy-lene, terfenadine, benzodiazepines, carbamazepine, and warfarin (for a complete list, see Nemeroff et ak, 1996). 

The SSRIs also have a high rate of protein binding, which can lead to increased therapeutic or toxic effects of other protein-bound medications. The MAOIs should not be given within 5 weeks after stopping fluoxetine, and at least 2 weeks after other SSRIS, because of the possibility of inducing a serotonergic syndrome. 

Steiner W, Eontaine R Toxic reaction following the combined administration of fluoxetine and L-tryptophan five case reports. Biol Psychiatry 21 1067-1071,... 

The side effects of antidepressants, sometimes very unpleasant, olten lead patients to interrupt their treatment or to reduce the drug dose, which involves a great risk in view of the high relapse rate and danger of suicide in depression. The newer antidepressants, such as trazodone, fluoxetine and other SSRIs and moclobemide, are characterized by better tolerability and lower toxicity and are therefore preferred in the treatment of outpatients and elderly patients (Rudorfer and Potter, 1989). A detailed list of general and specific common side effects associated with the newer generation of antidepressants is seen in Table 1.7. 

In contrast to anticonvulsants and alcohol, drugs such as bupropion, fluoxetine, fluvoxamine, nefazodone, quinidine, paroxetine, and some antipsychotics can inhibit specific CYP enzymes (7, 11, 36, 37, 41, 42, 43 and 44). Thus, TCAs, certain BZDs, bupropion, some steroids, and antipsychotics can all have their metabolism inhibited by drugs such as fluoxetine. For example, fluoxetine at 20 mg/day produces on average a 500% increase in the levels of coprescribed drugs which are principally dependent on CYP 2D6 for their clearance. That can lead to serious or even life-threatening toxicity if the drug has a narrow therapeutic index and the dose is not adjusted for the change in clearance caused by the coadministration of fluoxetine. 

SSRIs such as fluoxetine and paroxetine may inhibit the metabolism of antipsychotics, increasing their plasma levels and the chance for toxicity ( 517, 518). While antipsychotics may inhibit the metabolism of tricyclic antidepressants, or, in turn, have their metabolism inhibited by tricyclic antidepressants, the clinical relevance is uncertain. 

Salama AA, Shafey M. A case of severe lithium toxicity induced by combined fluoxetine and lithium carbonate [Letter]. Am J Psychiatry 1989 146 278. 

All SSRIs have an antipanic effect. Their advantages are limited adverse effects and lack of toxicity. Because of more acceptable adverse effect profiles, the SSRIs are usually the drugs of choice. Several studies consistently indicate that SSRIs such as fluoxetine, sertraline, paroxetine, fluvoxamine, as well as agents such as clomipramine and trazodone, all possess antipanic efficacy, although the last may be less effective than imipramine ( 24, 105, 106, 107, 108 and 109). 

BZD hypnotics such as midazolam and triazolam are primarily metabolized via the P450 3A3/4 microenzyme system. Other BZDs often used as hypnotics, such as diazepam, can also be metabolized by CYP 33/4 and CYP 2C19. Any drugs that act as inhibitors or inducers of these isoenzymes could increase or decrease BZD levels, respectively (350). Thus, ketoconazole, macrolide antibiotics (e.g., erythromycin), SSRIs (e.g., fluoxetine-norfluoxetine and fluvoxamine), and other antidepressants (especially nefazodone) may decrease clearance and increase BZD levels to potentially toxic ranges. Conversely, rifampacin, CBZ, and dexamethasone may increase clearance and decrease BZD levels to potentially subtherapeutic ranges. 

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