Nicola Montanaro

Safety of non-antiarrhythmic drugs that prolong the QT interval or induce torsade de pointes: an overview.

The long and growing list of non-antiarrhythmic drugs associated with prolongation of the QT interval of the electrocardiogram has generated concern not only for regulatory interventions leading to drug withdrawal, but also for the unjustified view that QT prolongation is usually an intrinsic effect of a whole therapeutic class [e.g. histamine H1 receptor antagonists (antihistamines)], whereas, in many cases, it is displayed only by some compounds within a given class of non-antiarrhythmic drugs because of an effect on cardiac repolarisation. We provide an overview of the different classes of non-antiarrhythmic drugs reported to prolong the QT interval (e.g. antihistamines, antipsychotics, antidepressants and macrolides) and discusses the clinical relevance of the QT prolonging effect. Drug-induced torsade de pointes are sometimes considered idiosyncratic, totally unpredictable adverse drug reactions, whereas a number of risk factors for their occurrence is now recognised. Widespread knowledge of these risk factors and implementation of a comprehensive list of QT prolonging drugs becomes an important issue. Risk factors include congenital long QT syndrome, clinically significant bradycardia or heart disease, electrolyte imbalance (especially hypokalaemia, hypomagnesaemia, hypocalcaemia), impaired hepatic/renal function, concomitant treatment with other drugs with known potential for pharmacokinetic/pharmacodynamic interactions (e.g. azole antifungals, macrolide antibacterials and class I or III antiarrhythmic agents). This review provides insight into the strategies that should be followed during a drug development program when a drug is suspected to affect the QT interval. The factors limiting the predictive value of preclinical and clinical studies are also outlined.The sensitivity of preclinical tests (i.e. their ability to label as positive those drugs with a real risk of inducing QT pronglation in humans) is sufficiently good, but their specificity (i.e. their ability to label as negative those drugs carrying no risk) is not well established. Verapamil is a notable example of a false positive: it blocks human ether-a-go-go-related (HERG) K+ channels, but is reported to have little potential to trigger torsade de pointes. Although inhibition of HERG K+ channels has been proposed as a primary test for screening purposes, it is important to remember that several ion currents are involved in the generation of the cardiac potential and that metabolites must be specifically tested in this in vitro test. At the present state of knowledge, no preclinical model has an absolute predictive value or can be considered as a gold standard. Therefore, the use of several models facilitates decision making and is recommended by most experts in the field.

QT-interval prolongation by non-cardiac drugs: lessons to be learned from recent experience

AbstractBackground: Evidence has accrued that several non-cardiac drugs may prolong cardiac repolarisation (hence, the QT interval of the surface electrocardiogram) to such a degree that potentially life-threatening ventricular arrhythmias (e.g. torsades de pointes) may occur, especially in case of overdosage or pharmacokinetic interactions. Discussion: This has fostered discussion on the molecular mechanisms underlying the class-III anti-arrhythmic effect shared by apparently disparate classes of drugs, on the clinical relevance of this side effect and on possible guidelines to be followed by drug companies, ethics committees and regulatory agencies in the risk–benefit assessment of new and licensed drugs. This review provides an update on the different classes of non-cardiac drugs reported to prolong the QT interval (e.g. histamine H1-receptor antagonists, antipsychotics, antidepressants and macrolides), on the possible underlying molecular mechanisms and on the clinical relevance of the QT prolonging effect. Identification and widespread knowledge of risk factors that may precipitate prolongation of the QT interval into life-threatening arrhythmias becomes an important issue. Risk factors include congenital long QT syndrome, clinically significant bradycardia or heart disease, electrolyte imbalance (especially hypokalaemia, hypomagnesaemia), impaired hepatic/renal function and concomitant treatment with other drugs with known potential for pharmacokinetic/pharmacodynamic interactions (e.g. azole antifungals, macrolide antibacterials and class-I or -III anti-arrhythmic agents). Future perspectives for drug research and development are also briefly outlined.

Adverse drug reactions related to the use of fluoroquinolone antimicrobials: an analysis of spontaneous reports and fluoroquinolone consumption data from three italian regions.

AbstractObjective: To analyse and compare with one another and with other antibacterial drugs the adverse drug reactions (ADRs) of the different fluoroquinolones currently used in Italy, spontaneously reported from doctors in three northern Italian regions. Methods: The data on fluoroquinolones and other antibacterials were obtained from the spontaneous reporting system database of Emilia Romagna, Lombardy and the Veneto, which are the principal contributors to the Italian spontaneous surveillance system. The fluoroquinolone ADRs with a causality assessment of certain, probable or possible (according to WHO criteria), reported between January 1999 and December 2001, were selected and toxicity profiles of individual drugs were described and compared with one another. The reports were also correlated with sex and age of patients and with regional prescription data to estimate individual fluoroquinolone reporting rate of adverse events. Results: During the study period, 10 011 reports were received by the system (a mean annual reporting rate of approximately 185 per million inhabitants): 1920 referred to systemic antimicrobials, of which 432 (22.5%) involved fluoroquinolones.Pefloxacin was associated with the highest reporting rate (982 reports/daily defined dose/1000 inhabitants/day), followed by moxifloxacin (356), rufloxacin (221) and lomefloxacin (196). The most frequently reported reactions to fluoroquinolones involved the skin, but their percentage (25%) was significantly lower (p < 0.01) than those of other systemic antimicrobials (58.5%), whereas the percentages of reactions involving the central nervous (12.2 vs 3.6%), musculoskeletal (14.7 vs 0.3%) and psychiatric systems (9.3 vs 1.8%) were significantly higher (p < 0.01). We found some significant differences in the safety profiles of individual fluoroquinolones: ciprofloxacin was more frequently associated with skin reactions (p < 0.01), levofloxacin and pefloxacin with musculoskeletal (p < 0.01), and rufloxacin with psychiatric disorders (p < 0.05). Levofloxacin was the fluoroquinolone associated with the highest rate of serious tendon disorders; phototoxic reactions were more frequent with lomefloxacin, and toxic epidermal necrolysis and Stevens-Johnson syndrome were seen only with ciprofloxacin. Conclusions: The differences in the safety profiles should be taken into account when prescribing a fluoroquinolone to individual patients.

Use of benzodiazepines in the Italian general population: prevalence, pattern of use and risk factors for use

Abstract This study was conducted to determine the prevalence and profile of use of benzodiazepines in the Italian population and risk factors for use. Between November 1992 and February 1993, 62 general practitioners submitted a validated self-administered questionnaire on health status and drug use to a randomised sample of 3100 subjects (≥ 18 years of age, stratified by sex and age), of whom 2803 responded (response rate 90.4%). Main outcome measures were point estimate (past-week) of all the drugs taken by each individual, dosage and length of use and source of the prescription. The overall past-week prevalence of use of benzodiazepines was 8.6% (5.0% males and 11.8% females). In the elderly (≥ 65 years) 18.8% reported current use (9.0% males and 24.7% females). Fifty-six per cent of the persons exposed to a benzodiazepine were chronic users (daily, for more than 6 months), and 70.1% in subjects ≥ 65 years. The average daily dose taken was relatively low: 61% of short-term users and 51% of chronic users used less than half a defined daily dose (DDD). Female sex, older age, unemployment and retirement were independently associated with the use of benzodiazepines. Benzodiazepine use in Italy appeared to be relatively high (about 9% of subjects reported current use 57% of whom were chronic users). Women were prescribed a benzodiazepine twice as often as men and one out of four elderly women was on treatment. Although the average dosage used was rather low, the high prevalence and the elevated proportion of chronic users should encourage drug information campaigns and educational interventions to promote a more conservative use of these drugs especially in the elderly.

Effect of chronic treatment with dizocilpine (MK-801) on the behavioral response to dopamine receptor agonists in the rat

The D2 or D1 dopamine receptor blockers (−)-sulpiride or SCH 23390 antagonized, in a dose dependent manner, the hypermotility induced by the N-methyl-d-aspartate (NMDA) receptor antagonist, MK-801 (0.25 mg/kg IP). MK-801 induced hyperactivity was not detected when rats were observed on days 7, 14 or 21 of 21 daily injections of MK-801. This lack of hyperactivity was also noted 5 days after the last administration of the repeated treatment with MK-801. The hypermotility induced by the D2 dopamine receptor agonist LY 171555 (0.3 mg/kg IP) was reduced 5 days following repeated treatment (21 days) with MK-801, while no change in the behavioral responses to the selective D1 agonist, SKF 38393, or the mixed D1/D2 agent apomorphine was detected. The results, although suggesting the involvement of dopaminergic pathways in the behavioral effect of MK-801, are conflicting with regard to the underlying mechanisms and to the adaptive changes of dopaminergic system following repeated NMDA receptor blockade.

Time course of rat motility response to apomorphine: A simple model for studying preferential blockade of brain dopamine receptors mediating sedation

The present work proposes a simple behavioral method for studying the ability of certain neuroleptics to block preferentially dopamine receptors subserving sedation. The model is based on the temporally biphasic motor response induced in rats by a single critical dose of apomorphine. It was chosen from a preliminary apomorphine dose-response study which showed that the same doses between 6.25 and 625 μg/kg affected rat motility differently according to whether the animals were “naive” or “familiarized” to the apparatus for 90 min before administering the drug. When the motility response of naive rats to 300 μg/kg of apomorphine was recorded immediately after SC injection, an initial (1–5 min) inhibition and a subsequent (20–45 min) stimulation of motility were obtained. (-)-Sulpiride (1.25–50 mg/kg) was found to be approximately 6-fold more effective in counteracting the apomorphine inhibition than stimulation of locomotion. Haloperidol (0.005–0.1 mg/kg) incompletely antagonized apomorphine inhibition and markedly blocked stimulation, which suggests that it has no preferential activity on dopamine receptors subserving sedation. The results were in accordance with those obtained by other authors with different paradigms, and indicated that the time course of the rat motility response to a single dose of apomorphine may constitute a useful model for detecting selective influences on different dopamine receptors.

Changes in behavioural responses to the combined administration of D1 and D2 dopamine agonists in normosensitive and D1 supersensitive rats

The selective D1 receptor stimulant SKF 38393 dose-dependently increased grooming time in rats without affecting locomotor activity or eliciting stereotyped behaviour. The selective D2 receptor agonist LY 171555 induced a dose-dependent increase in rat motility, a marked decrease in grooming time and a low occurrence of stereotyped behaviour. Concurrent administration of the two selective agonists induced high-degree stereotyped responses and reductions in locomotor and grooming behaviours. Rats withdrawn from repeated treatment with the selective D1 receptor blocker SCH 23390 (0.05 mg/kg twice daily for 21 days; 7 days of washout) did not exhibit any change of locomotor and grooming responses to threshold doses of LY 171555 and SKF 38393 given alone or in combination. On the contrary, a significantly greater occurrence of high-degree stereotyped responses to the combination of the two selective agonists was observed. The data support the view that D1 and D2 receptors have a cooperative role in the generation of stereotypies and suggest that D1 receptor supersensitivity needs D2 stimulation to be revealed.

Use of lipid-lowering drugs from 1990 to 1994: an international comparison among Australia, Finland, Italy (Emilia Romagna Region), Norway and Sweden.

AbstractObjective: To compare the overall utilisation patterns of lipid-lowering drugs between 1990 and 1994 in Australia, Finland, Italy, Norway and Sweden as well as the pattern of use with respect to age and gender in Italy and Sweden. Methods: Data were retrieved from regulatory authorities in each country for the 5-year period and analysed according to the ATC/DDD methodology (Anatomical Therapeutic Chemical classification/Defined Daily Doses). Utilisation was calculated as the DDDs for 1000 inhabitants per day for all drugs of the ATC category B04 (serum lipid-reducing agents). Data from Sweden and Italy were also compared with respect to gender and age. Results: In 1994, Australia demonstrated the highest degree of utilisation (11.9 DDD) and the Nordic Countries the lowest (Sweden 5.6; Norway 4.9; Finland 4.0). In all countries except Italy, a steady increase was observed; in Italy, utilisation of these drugs reached a maximum in 1992 (11.5 DDD), but then underwent a reduction which was caused by restrictions in the reimbursement status in 1993 (10.4) and 1994 (6.7). Administration of statins increased in all countries, becoming the most used group of the B04 class. In 1988, the number of different drugs listed by each national health service ranged from 4 (Norway) to 16 (Italy); in 1994 it ranged from 6 (Norway) to 9 (Sweden). Analysis with respect to gender showed the opposite pattern in Sweden (males 4.6 and females 3.3 in 1992; 6.2 and 4.5, respectively, in 1994) than in Italy (males 10.8 and females 17.8 in 1992; 6.4 and 9.2, respectively, in 1994). Exposure was highest in people aged 60–69 years in both countries, followed by age group 50–59 in Sweden and 70–79 in Italy. Conclusions: Large variations in the utilisation of lipid-lowering drugs exist between countries, with Australia and Italy much higher than others. Of the drugs in the ATC category B04, the use of statins predominates in all countries, but to varying degrees. The large difference in the degree of drug utilisation with respect to age and gender between Italy and Sweden suggests major deviations from evidence-based medicine.

Drug-induced anaphylaxis : case/non-case study based on an italian pharmacovigilance database.

AbstractObjective: To identify the number of cases of anaphylaxis reported in association with different classes of drugs and compare it with other reports contained in the same database. Methods: The data were obtained from a database containing all of the spontaneous reports of adverse drug reactions (ADRs) coming from the Italian regions of Emilia Romagna, Lombardy and the Veneto, which are the main contributors to the Italian spontaneous surveillance system. The ADRs reported between January 1990 and December 2003 with a causality assessment of certainly, probably or possibly drug related (according to the WHO criteria) were analysed using a case/non-case design. The cases were defined as the reactions already coded by the WHO preferred terms of ‘anaphylactic shock’ or ‘anaphylactoid reaction’ (this last term also included anaphylactic reaction) and those with a time of event onset that suggested an allergic reaction and involved at least two of the skin, respiratory, gastrointestinal, CNS or cardiovascular systems; the non-cases were all of the other ADR reports. The frequency of the association between anaphylaxis and the suspected drug in comparison with the frequency of anaphylaxis associated to all of the other drugs was calculated using the ADR reporting odds ratio (ROR) as a measure of disproportionality. Results: Our database contained 744 cases (including 307 cases of anaphylactic shock with 10 deaths) and 27 512 non-cases. The percentage of anaphylaxis cases reported in inpatients was higher than that among outpatients (59.1% vs 40.9%). This distribution is significantly different from that of the other ADR reports that mainly refer to outpatients. After intravenous drug administrations, anaphylactic shock cases were more frequent than anaphylactoid reactions or other ADRs, but more than one-third of these reactions were caused by an oral drug. Blood substitutes and radiology contrast agents had the highest RORs. Among the systemic antibacterial agents, anaphylaxis was disproportionally reported more often for penicillins, quinolones, cephalosporins and glycopeptides, but diclofenac was the only NSAID with a significant ROR. As a category, vaccines had a significantly lower ROR, thus indicating that anaphylaxis is reported proportionally less than other ADRs. Conclusions: Anaphylaxis is a severe ADR that may also occur with commonly used drugs. It represents 2.7% of all of the ADRs reported in an Italian spontaneous reporting database.

Responses to selective D-1 and D-2 agonists after repeated treatment with selective D-1 and D-2 antagonists

This study was aimed at achieving a better understanding of the functional role of D-1 and D-2 receptors in some dopamine-mediated behaviors. Hypermotility, grooming behavior and stereotyped behavior were induced, respectively, by LY 171555 (D-2 agonist), SKF 38393 (D-1 agonist) and apomorphine (mixed agonist). Acute pretreatment either with the D-1 selective antagonist SCH 23390 (0.02 mg/kg) or with the D-2 receptor blocker YM 09151-2 (0.02 mg/kg, IP) blocked all these behaviors, suggesting the existence of functional interactions between D-1 and D-2 receptors. Striatal membranes prepared from rats receiving repeated administrations with SCH 23390 (0.05 mg/kg, twice daily for 21 days) showed an increase in the number of D-1 but not of D-2 receptors. On the contrary the repeated treatments with YM 09151-2 increased only the Bmax values of D-2 receptors. While the D-1 supersensitive rats showed only enhancement of apomorphine-induced stereotyped behavior, the D-2 supersensitive rats exhibited an increase of both apomorphine-elicited stereotypy and LY 171555-elicited hypermotility. SKF 38393-induced grooming was unaffected by any pretreatments. Moreover when D-2 supersensitive rats were acutely pretreated with SCH 23390, the enhancement of apomorphine-induced stereotyped behavior was abolished. It is concluded that the behavioral expression of D-1 receptor supersensitivity requires the simultaneous activation of D-1 and D-2 receptors.