Based on sales data and spontaneous reporting of adverse drug reactions in Sweden, the risk of agranulocytosis with dipyrone seems to be considerably higher than the previously estimated risks. Dipyrone is also associated with other blood dyscrasias, and the prognosis for combined dyscrasias seems to be poorer than for isolated agranulocytosis.
The use of psychotropic drugs has been associated with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in a number of case reports. SIADH is characterised by the sustained release of antidiuretic hormone (ADH) from the posterior pituitary. The patients have a reduced ability to excrete diluted urine, ingested fluid is retained, and the extracellular fluid expands and becomes hypo-osmolar. The cardinal signs are hyponatraemia, serum hypoosmolality and a less than maximally diluted urine. Common symptoms include weakness, lethargy, headache, anorexia and weight gain. These symptoms may be followed by confusion, convulsions, coma and death. The early symptoms are vague and nonspecific, and they may even mimic the symptoms of the psychiatric disorder itself. For antidepressants, the risk of SIADH seems to be highest during the first weeks of treatment. For antipsychotics, the risk seems to be more spread out in time. The causative role of the drug may sometimes be difficult to estimate, as even drug-free psychiatric patients, mostly those with schizophrenia, develop SIADH on the basis of psychogenic polydipsia. Smoking is another factor associated with the development of SIADH, and the risk may also increase with age. The acute treatment of SIADH induced by a psychotropic drug includes discontinuation of the drug as well as restriction of fluid intake. In cases with significant clinical symptoms, infusion of sodium chloride is recommended. After the acute management, it is useful to evaluate the causative role of the drug by performing a water loading test and/or drug rechallenge. If continued treatment with an antidepressant or antipsychotic is indicated, a drug with a different pharmacological profile should be chosen, and the serum sodium levels should be monitored closely. If treatment with the drug that caused SIADH must be continued, concomitant treatment with demeclocycline may reduce the tendency of hyponatraemia.
Smokers had lower serum concentrations of fluvoxamine than nonsmokers after a single oral dose of fluvoxamine. This finding is consistent with a possible role of CYP1A2 in fluvoxamine metabolism.
The risk of EPS with SSRIs seems to increase with advanced age and with the presence of the A1 allele of DRD2 Taq1A polymorphism. Because of the small sample size of our study and the use of historical controls rather than patients who did not experience EPS during SSRIs treatment, the DRD2 finding is preliminary and needs to be replicated in other studies before firm conclusions can be drawn. At least 1 additional potential risk factor was found in almost all cases.
All adverse drug reaction reports labelled seizures or myoclonus during treatment with antidepressants and stored in the Swedish national database for spontaneous reporting of adverse drug reactions were reviewed in order to evaluate possible risk factors. The reporting physicians were contacted and asked for complementary information, and blood samples for determination of the CYP2D6 and CYP2C19 genotypes were obtained from patients available. In total, 25 cases of seizures and 7 cases of myoclonus were studied. The drugs included were maprotiline (n=8), mianserin (n=7), fluvoxamine (n=6), amitriptyline (n=3), clomipramine (n=3), citalopram (n=2), paroxetine (n=2) and lofepramine (n=1). Previously suggested predisposing factors were identified in all but four cases (87%). None of the 11 patients genotyped were found to be poor metabolizers with respect to the enzymes CYP2D6 or CYP2C19. Thus, neither the CYP2D6 nor the CYP2C19 genotype were found to be associated with the occurrence of seizures/myoclonus during treatment with antidepressants. However, 15 patients (47%) were concomitantly treated with drugs with potential inhibitory effects on CYP2D6, such as neuroleptics and dextropropoxyphene, and the patients might thus have been converted from the extensive metabolizer to the poor metabolizer phenotype during this treatment. Concomitant treatment with drugs decreasing the seizure threshold and/or inhibiting the metabolism of antidepressants appeared to be an important risk factor for the occurrence of seizures/myoclonus.
The symptoms and possible risk factors of peripheral sensory disturbances related to fluoroquinolones are reviewed on the basis of 37 reports submitted to the Swedish Adverse Drug Reactions Advisory Committee. In 25 patients (68%), symptoms occurred within 1 week after start of treatment. Paraesthesia was the most common complaint and occurred in 81% of the cases. Fifty-one per cent of the reports concerned numbness/hypoaesthesia, 27% pain/hyperaesthesia and 11% muscle weakness. Seventy-one per cent of the patients recovered within 2 weeks after drug discontinuation. Possible predisposing factors were impaired renal function, diabetes, lymphatic malignancy and treatment with another drug known to cause neuropathy.
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