Risk of extrapyramidal syndromes with haloperidol, risperidone, or olanzapine

OBJECTIVE

To compare the risk of extrapyramidal syndrome (EPS) between risperidone, olanzapine, and haloperidol, taking into account patients' past antipsychotic drug use and past EPS.

METHODS

Data were obtained from the PHARMO-database, containing filled prescriptions of 450,000 community-dwelling people in the Netherlands from 1986 through 1999. We defined cohorts of first-time users of haloperidol, risperidone, or olanzapine aged 15 to 54 years. In the first 90 days of treatment, we assessed the occurrence of EPS, defined as first use of any antiparkinsonian agent. We estimated relative risks of EPS for risperidone and olanzapine versus haloperidol using a Cox proportional hazards model. Patients were subdivided according to prior use of antipsychotic and antiparkinsonian drugs.

RESULTS

We identified 424 patients starting treatment with haloperidol, 243 with risperidone, and 181 with olanzapine. Prior use of antipsychotic plus antiparkinsonian medication was significantly more frequent among users of risperidone and olanzapine than in those using haloperidol (36.2%, 40.3%, and 4.5%, respectively; p < 0.001). Within most subgroups of comparable treatment history, patients using risperidone and olanzapine showed reduced risks of EPS compared with haloperidol, although some of these findings did not reach statistical significance (RR 0.03-0.22). However, this was not observed for patients using risperidone who had experienced EPS in the past (RR 1.30; 95% CI 0.24 to 7.18).

CONCLUSIONS

In general, we observed reduced risks of EPS for risperidone and olanzapine compared with haloperidol within subgroups of patients with a similar treatment history. However, the added value of risperidone in patients who have experienced EPS in the past needs further study.

Long-term therapy with spironolactone

OBJECTIVE

To evaluate the duration of therapy with spironolactone in daily practice.

METHOD

A retrospective follow-up of a cohort of patients with a first prescription for spironolactone between January 1, 1990 and December 31, 1996 and at least one hospital discharge for CHF in the preceding year.

RESULTS

243 patients met the inclusion criteria and were followed until the end of data collection. The average starting dosage of spironolactone was 55 mg. 143 patients (58.8%) discontinued spironolactone therapy before the end of follow-up. 98 patients (40.8%) discontinued within 6 months of follow-up. Of the 137 patients (56.4%) who did use spironolactone and an ACE-inhibitor concomitantly, only 45 (32.8%) continued this combination until the end of follow-up. The remainder of the patients discontinued either the ACE-inhibitor (10.9%) or spironolactone (12.4%) or both (43.8%).

CONCLUSION

While the reasons for discontinuation remain unclear, our data suggest that it is difficult to keep patients on both drugs. It is not certain whether these findings from past spironolactone use can be extrapolated to future use. Patients in the general population received higher average spironolactone dosages compared to the RALES study (55 mg vs. 26 mg), possibly resulting in more adverse effects and partly explaining the high discontinuation rate.

Antipsychotic-induced extrapyramidal syndromes. Risperidone compared with low- and high-potency conventional antipsychotic drugs

AIM

To compare the risk of extrapyramidal syndromes (EPS) between patients using risperidone and those using low-potency conventional antipsychotic drugs (APDs) in outpatient clinical practice, as measured by the use of anticholinergic medication. We tried to replicate results from previous clinical trials that compared risperidone with high-potency APDs.

METHOD

Data was obtained from the PHARMO database containing filled prescriptions of 450,000 community-dwelling people in The Netherlands from 1986 to 1998. From the patients aged 15-54 years who had been newly treated with APDs, we defined mutually exclusive cohorts according to the APD first prescribed to a patient. APD exposure was followed until the first prescription of anticholinergic medication and was censored when APD prescribing was interrupted or switched. We estimated relative risks between risperidone and commonly used low-potency and high-potency APDs using Cox proportional hazards models, adjusting for age, gender, dose and other potential confounders.

RESULTS

In 4094 patients who had been newly prescribed antipsychotic drugs, the overall incidence rate of anticholinergic drug therapy was 556 per 1000 person-years, which was dose dependent. Prescribed doses of all antipsychotics were low. While, in accordance with previous trials, risperidone showed a lower risk of EPS than the high potency APDs such as haloperidol (RR 0.26; 95% CI 0.10-0.64), we did not observe a lower EPS rate than low-potency APDs (risperidone vs thioridazine RR 1.73, 95% CI 0.49-6.13; risperidone vs pipamperone RR 2.50, 95% CI 0.78-8.04).

CONCLUSION

The reduced EPS rates observed when comparing risperidone with high-potency antipsychotics such as haloperidol may not apply to comparisons with low-potency drugs.

Fluoroquinolone use and the change in incidence of tendon ruptures in the Netherlands

INTRODUCTION

Shortly after their introduction, fluoroquinolones were associated with reports of tendinitis and tendon rupture. During the past years, the number of reports has risen, possibly because of an increased use of fluoroquinolones. In this study, we describe the use of fluoroquinolones in the Dutch community and the possible public health effects of an association between fluoroquinolone use and tendon ruptures.

METHODS

In the PHARMO drug database we identified all prescriptions for fluoroquinolones in the period 1991-1996. The incidence of fluoroquinolone use was expressed as the number of fluoroquinolone episodes per 1000 inhabitants in one year, and extrapolated to the Dutch population after standardisation on age and gender. The annual incidence of non-traumatic tendon ruptures in the period 1991-1996 was calculated with data from the nation-wide hospital registry. The expected number of fluoroquinolone attributable tendon ruptures was calculated on the basis of the use of fluoroquinolones, the number of non-traumatic tendon ruptures and an assumed relative risk of 1.5-10.

RESULTS

In 1996, approximately 251,000 patients experienced 318,000 episodes of fluoroquinolone use in the Netherlands. Females used more often fluoroquinolones than males, and the number of episodes increased exponentially with age. In the period 1991 through 1996, the absolute number of fluoroquinolone episodes increased by 160%, from 122,000 to 318,000. The absolute number of hospitalised tendon ruptures increased with 28%, from 768 in 1991 to 984 in 1996. Assuming a relative risk of 1.5 to 10.0, 1 to 15 tendon ruptures could be attributed to fluoroquinolone use in 1996. Only 7% of the observed increase could be attributed to the increased use of fluoroquinolones. If the total increase of hospitalised non-traumatic tendon ruptures would be attributable to the increase in fluoroquinolone use, this would mean that the risk of non traumatic tendon ruptures to fluoroquinolones would be more than 250 times the risk during non-use.

CONCLUSION

In the Netherlands, a large simultaneous increase in non-traumatic tendon ruptures and fluoroquinolone use was observed in the period between 1991 to 1996. Assuming a relative risk of 1.5 to 10.0 for tendon ruptures during fluoroquinolone use, only 0.5 to 7% of the increase in non-traumatic tendon ruptures could be attributed to the increased fluoroquinolone use. The increase in the incidence of non-traumatic hospitalised tendon ruptures in the Netherlands is not likely to be explained solely by the increased use of fluoroquinolones.

Tendon disorders attributed to fluoroquinolones: a study on 42 spontaneous reports in the period 1988 to 1998

OBJECTIVE

Fluoroquinolone antibiotics have been associated with tendinitis and tendon rupture. In this paper we report on the followup of 42 spontaneous reports of fluoroquinolone-associated tendon disorders.

METHODS

This study is based on cases of fluoroquinolone-associated tendon disorders reported to the Netherlands Pharmacovigilance Foundation Lareb and the Drug Safety Unit of the Inspectorate for Health Care between January 1, 1988, and January 1, 1998. By means of a mailed questionnaire, we collected information on the site of injury, onset of symptoms, treatment, and course of the tendon disorder as well as information on possible risk factors and concomitant medication.

RESULTS

Of 50 mailed questionnaires, 42 (84%) were returned. The data concerned 32 patients (76%) with tendinitis and 10 patients (24%) with a tendon rupture. Sixteen cases (38%) were attributed to ofloxacin, 13 (31%) to ciprofloxacin, 8 (19%) to norfloxacin, and 5 (12%) to pefloxacin. There was a male predominance, and the median age of the patients was 68 years. Most of the reports concerned the Achilles tendon, and 24 patients (57%) had bilateral tendinitis. The latency period between the start of treatment and the appearance of the first symptoms ranged from 1 to 510 days with a median of 6 days. Most patients recovered within 2 months after cessation of therapy, but 26% had not yet recovered at followup.

CONCLUSION

These reports suggest that fluoroquinolone-associated tendon disorders are more common in patients over 60 years of age. Ofloxacin was implicated most frequently relative to the number of filled prescriptions in the Netherlands.

Determinants of pharmacists' interventions linked to prescription processing

AIM OF STUDY

The role of pharmacists in today's healthcare is changing rapidly. As they are close to the prescribing process, pharmacists are in the position to identify and adjust prescribing errors before dispensing. The objective of this study was to identify relevant determinants of interventions directly linked to prescription processing in community pharmacy.

METHODS

As part of a yearly continuing education programme, all community pharmacies in the region of 'Zealand' (N = 23) in the south-west of The Netherlands kept detailed records of all interventions directly linked to prescription processing during one week in May 1998. For every patient involved in an intervention, a control-patient was matched on pharmacy practice, date, gender and age.

RESULTS

A total of 39,357 prescriptions were evaluated by the 23 pharmacies during the one-week intervention programme. Out of these, one out of 10 resulted into an intervention. Being a first prescription in a new treatment episode was found to be a significant determinant (OR 1.75, 95 CI% 1.18-2.33). Variables reflecting drug therapy complexity (> 3 prescribers, > 15 prescriptions in 3 months before, > 3 different medications) showed all ORs higher than 1.00, but not significant. When looking at the individual drug categories, anti-infectives, respiratory drugs and cardiovascular medicines came out as important drug classes for intervention risk. We could not find any association between the number of signals per pharmacy and the number of interventions.

CONCLUSION

The 'whistle-blower' model of pharmacy based interventions is a valid one but needs a targeted and integral way of implemented thinking and use of information technology. In such an environment, interventions are a logical step of in-process quality control in the drug usage system.

Evaluating adverse cardiovascular effects of drug treatment for benign prostatic hyperplasia (BPH): methodological considerations

When studying the effects of drug exposure in diseases with a long asymptomatic clinical course, exposure classification may be biased by the gradually developing "visibility" of the disease. Benign prostatic hyperplasia (BPH) is such a disease. We found that cardiovascular morbidity is two times more prevalent in patients starting drug treatment for BPH when compared to age-matched population controls. This resulted in a difference of cardiovascular prognostic factors between the exposed and non-exposed. This feature can jeopardize the validity of non-randomized comparisons of drug effects. Moreover, the existence of non-treatment strategies, disease under-reporting, and an elderly population with a high baseline risk of experiencing (cardiovascular) outcome events were encountered as methodological problems. When studying adverse cardiovascular effects in patients using BPH products in a non-randomized fashion, an important question is whether we can measure in the database all relevant prognostic factors and use the information for statistical adjustment. This question is an important challenge to observational research and once again stresses the need for control of possible biases in choosing an appropriate study design.

Quick titration of pergolide in cotreatment with domperidone is safe and effective

The purpose of the study was to analyze efficacy and safety of quick pergolide titration combined with domperidone. In an open-label prospective study, pergolide was titrated in 16 days to a maximum of 3 mg/d doses as adjunctive treatment to L-Dopa in 10 elderly patients with Parkinson's disease. Sixty milligrams domperidone was started 2 days before and and continued during the pergolide titration period to prevent side effects. Adverse events were studied for 6 weeks. Efficacy was measured with the motor part ("on" condition) of the Unified Parkinson's Disease Rating Scale (UPDRS), the 2-minute walking test, the Timed Up and Go test, and the Postural-Locomotor-Manual test. After quick titration of pergolide with domperidone cotreatment, no symptomatic side effects were seen except for lightheadedness in one patient, which disappeared after dose reduction. The UPDRS motor score improved significantly from 21 +/- 8 at baseline to 16 +/- 7 and 12 +/- 7 after 1 and 2 weeks, respectively. The 2-minute walking distance improved significantly from 123 +/- 36 m at baseline to 136 +/- 41 m after 6 weeks. The Timed Up and Go and Postural-Locomotor-Manual test results, overall, did not show significant changes. Quick titration of pergolide to a maximum of 3 mg/d with domperidone cotreatment is safe and effective. Therefore, we recommend domperidone cotreatment in the titration period to prevent unnecessary failure of dopamine agonist treatment because of adverse effects.

An epidemiological approach to assess the economic burden of NSAID-induced gastrointestinal events in The Netherlands

OBJECTIVE

To use the population attributable risk (PAR) to estimate the treatment costs resulting from nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal (GI) morbidity.

DESIGN

Two case-control studies with the following outcomes: (i) the start of therapy with gastroprotective agents (GPAs) and (ii) hospitalisations for GI events.

SETTING

Community-dwelling inhabitants of defined areas in The Netherlands covering the period 1989 to 1998. All analyses were performed from the perspective of a third-party payer.

METHODS

Risk and exposure data were obtained from the Dutch PHARMO system, a population-based register of drug-dispensing records and hospital records. The PAR was estimated based on stratum-specific prevalence estimates of NSAID use and the corresponding odds ratios (ORs) obtained from the case-control studies. Cost data were obtained from Dutch national hospital discharge records and tariffs. Annual treatment costs of NSAID-induced GI events were calculated based on the PAR in the sample population and extrapolated to the total population using national demographic data.

RESULTS

The adjusted ORs for starting GPA use and hospitalisation for GI events were 6.6 [95% confidence interval (CI): 5.5 to 7.8] and 5.0 (95% CI: 4.0 to 6.2), respectively, in NSAID users compared with controls. Variation of OR with age among NSAID users suggested that prevention of GI events is most efficient among the elderly. The total annual cost (1998 values) of GPA use and hospitalisations for GI events attributable to the use of NSAIDs was 59 million euro (EUR) [95% CI: EUR38.5 million to EUR98 million]. More than 65% of these NSAID-induced costs, EUR38 million, can be attributed to long term users of NSAIDs, representing only 9.3% of all users of NSAIDs.

CONCLUSIONS

The PAR can be used to estimate the costs of drug-induced morbidity and changes in costs resulting from substitutions with other drugs. For each EUR1.00 spent on NSAIDs, an additional EUR0.68 (excluding costs for prophylactic treatment) can be added for the treatment of GI adverse events.

Use of sympathomimetic drugs leads to increased risk of hospitalization for arrhythmias in patients with congestive heart failure

BACKGROUND

Sympathomimetic agents have a direct positive chronotropic effect on heart rate and may cause hypokalemia, even when administered by inhalation. In selected patients (e.g., patients with congestive heart failure [CHF]) this can lead to arrhythmias. Despite the potential adverse effects of these agents, they are used frequently in patients with CHF, due to a high incidence of respiratory comorbidity. This study investigates the effects of sympathomimetics on the incidence of hospitalizations for arrhythmias in patients with CHF.

METHODS

In a cohort of 1208 patients with a validated hospital discharge diagnosis of CHF, we identified 149 cases with a readmission for arrhythmias, and compared these in a nested matched case-control design with 149 controls from the remainder of the cohort with no hospital readmission for any cardiac cause. Conditional logistic regression was used to calculate the risk for hospitalization for arrhythmias associated with exposure to sympathomimetic agents, expressed as odds ratios.

RESULTS

Of 149 case patients, a total of 33 (22.1%) were treated with any sympathomimetic agent, and 6 patients (4.0%) were treated with systemic sympathomimetics. The use of any sympathomimetic drug was associated with an increased risk of admission for arrhythmia (odds ratio, 4.0; 95% confidence interval, 1.0-15.1). For systemic sympathomimetic drugs, the corresponding odds ratio was 15.7 (95% confidence interval, 1.1-228.0).

CONCLUSIONS

The results of this study strongly suggest an increased risk of hospitalization for arrhythmias in patients with CHF treated with sympathomimetic drugs. Sympathomimetics should be given under close surveillance to patients with CHF.

Cyclical etidronate use is not associated with symptoms of peptic ulcer disease

OBJECTIVE

To investigate whether the alkylbisphosphonate etidronate is associated with an increased risk of gastrointestinal symptoms.

METHODS

We conducted an observational follow-up study on a possible relationship between etidronate use and the risk of gastrointestinal symptoms in a cohort of 2754 women over 50 years of age. The study was performed with data on drug prescriptions obtained from the PHARMO database in the Netherlands. Women were included when they used either cyclical etidronate (n = 1050) or estrogen (n = 1704) for at least 14 days. They were followed-up for incident use of antiulcer drugs while on exposure medication.

RESULTS

The mean ages were 72 years and 59 years in the etidronate and estrogen groups, respectively. In total, there were 95 women with incident prescriptions for gastrointestinal events after a median duration of follow-up of 2.7 months (range 0.1-19.4 months). The crude relative risk of a gastrointestinal event for etidronate compared with estrogen use was 1.2 [95% confidence interval (95% CI) 0.8-1.8]. Adjusted for baseline age, use of corticosteroids, salicylates and nonsteroidal anti-inflammatory drugs, the relative risk reversed to 0.6 (95% CI 0.4-1.2).

CONCLUSION

The use of cyclical etidronate is not associated with an elevated risk of symptoms of peptic ulcer disease.

Use of prevalence and incidence measures to describe age-related prescribing of antidepressants with and without anticholinergic effects

To evaluate whether physicians avoid prescribing highly anticholinergic antidepressants (AAD) in the elderly, a population-based retrospectively data analysis was performed using databases from a Dutch health insurance company. Data collected on approximately 240,000 persons covered the period from 1 July 1993 to 1 January 1996. The prevalence and the incidence (number of new starters) of antidepressant use was measured over 1994 and 1995. Use of AAD was proportionally higher in the elderly in terms of both prevalence and incidence rates; the ratio of starters of AAD versus starters of non-AAD in 1994 increased steadily with age (from 0.54 in the age group 20-29 to 1.15 in the age group 60-69). In 1995 these incidence ratios decreased (0.41 to 0.99, respectively); however, the decrease was higher in the younger age groups. The data indicate that in the population studied, physicians do not refrain from prescribing highly anticholinergic agents to older patients despite their potential adverse drug reactions in this age group. This study also indicates that prevalence and incidence rates can be extracted from reimbursement data and give insight into actual prescribing practices.

Influence of question structure on the recall of self-reported drug use

Epidemiological studies often rely on self-reported information as a source of drug exposure. Several studies have evaluated the accuracy of self-reported information on drug use. The influence of question structure on the accuracy of recall, however, has not been studied extensively in these studies. In this study we examined the recall accuracy of questionnaire information on drug use in a ongoing public health survey with special attention to the influence of question structure on sensitivity of recall. A sample of 372 hypertensive subjects for whom questionnaire information and pharmacy records were available was examined. Self-reported information on drug use was obtained through questions about medications used for a specific condition and one final open-ended question. This information was compared with the pharmacy medication history. About 71% of all drugs that were currently in use according to the pharmacy records were recalled through the self-administered questionnaire, and 94% of all drugs mentioned in the questionnaire could be traced in the pharmacy records. Recall sensitivity was higher for questions about medications used for a specific indication (88%) than for the open-ended question (41%). The type of drug that was used might have caused part of this difference in recall. We conclude that questionnaire structure might be of influence on the accuracy of recall of self-reported drug use, and more attention should be paid to the structure of questions on drug use.

Agreement between self-reported antihypertensive drug use and pharmacy records in a population-based study in The Netherlands

From 1987 to 1991, over 36,000 men and women aged 20-59 years have been examined in the Monitoring Project on Cardiovascular Disease Risk Factors in The Netherlands. Classification of the treatment status of hypertensives in this population-based study was based on self-administered questionnaires. In order to assess the accuracy of self-reported antihypertensive drug use we compared the questionnaire information with computerized pharmacy records from a sample of 372 hypertensive subjects. Most antihypertensive drugs that were mentioned in the questionnaire were present in the pharmacy medication history (93%). However, this percentage was less (76%) when a comparison was made with the calculated duration of use based on the number of units prescribed and the directions for use in the pharmacy records. About 94% of the hypertensive subjects who were using an antihypertensive drug according to the pharmacy records, also mentioned at least one antihypertensive drug in the questionnaire. Agreement between self-reported antihypertensive drug use and pharmacy records was consistently high for all classes of antihypertensive drugs. Among 321 (86%) subjects, the number and types of self-reported antihypertensive drugs were exactly the same as in the pharmacy records. In conclusion, the agreement between self-reported antihypertensive drug use and pharmacy records was high, and the self-reported questionnaire information on antihypertensive drug use can be reliably used for the classification of treatment status of hypertensive subjects in this population-based study.

Venous thromboembolism among new users of different oral contraceptives

New use of third generation oral contraceptives is associated with a four-fold increased risk of venous thromboembolism compared with users of second generation oral contraceptives, particularly among young, healthy women.

Asthma exacerbations during first therapy with long acting beta 2-agonists

Long-acting beta 2-agonists (LBA) have become an important therapeutic strategy in the treatment of asthma. There is, however, debate whether LBA increase the risk of asthma exacerbations (AE). We studied whether the risk of AE was increased in patients starting LBA therapy and whether the risk was associated with severity. Patients, aged 5-49 years, who were firstly prescribed LBA between 1992 and 1995, and who had at least two consecutive prescriptions of LBA, were selected from the PHARMO-RLS database. The exposure period was the interval between the first and last dispensing of the first exposure episode. The year before the onset was the control period. Single short courses of oral glucocorticosteroids or antibiotics were used as proxy indicators for AE. Severity indicators, assessed in the 6 months before initiation of LBA, were used to classify patients' severity. A total of 788 patients met the inclusion criteria (men: 45.1%, median age: 35). The incidence rate of AE increased significantly (p < 0.001) with severity from 1.7 to 2.4 and 1.1 to 2.7 AE per person year in index and control period, respectively. The risk was merely elevated among patients who start LBA therapy without being treated with other anti-asthma drugs before (RR 1.4, 95% CI 1.0-2.2). First starters of LBA showed no overall change in incidence of AE when compared with the year before starting treatment. A total of 6.9% of patients used LBA as step-one therapy. These patients suffer, in contrast to the whole population, a 40% increased risk of having AE. Although this could be due to confounding, we recommend being reluctant to prescribe LBA to patients who have not been treated before with other anti-asthma drugs.

A population-based case-cohort study of drug-associated agranulocytosis

BACKGROUND

Agranulocytosis is a life-threatening disorder, often caused by drugs. Incidences or risks of drug-induced agranulocytosis are not well known, since it is rare.

METHODS

To determine the risk of drug-associated agranulocytosis as a reason for admission to Dutch hospitals, we performed a population-based case-cohort study. Hospital discharge data came from the Dutch Centre for Health Care Information, Utrecht, which contains data on all general and university hospitals in the Netherlands. The reference cohort consisted of all persons in the catchment area of the Pharmaco Morbidity Record Linkage System (PHARMO RLS) in the Netherlands, composing a population of approximately 220 000 to 484 000 persons from 1987 through 1990. All admissions during that period with agranulocytosis or related diagnoses were included in the study (n = 923). The potential causes of agranulocytosis were assessed in all cases classified as probable or possible agranulocytosis.

RESULTS

Discharge summaries were received of 753 admissions, of which 678 contained enough information for analysis. Of the 678,108 were classified as "agranulocytosis probable" or as "agranulocytosis possible." In 75 of these 108 cases, agranulocytosis had been the reason for admission. Fifteen patients had used methimazole within 10 days before developing agranulocytosis; 2, carbimazole; 9, sulfasalazine; 8, sulfamethoxazole-trimethoprim; 4, clomipramine hydrochloride; and 2, dipyrone with analgesics, yielding adjusted relative risks of agranulocytosis of 114.8 (for thyroid inhibitors combined) (95% confidence interval [CI], 60.5-218.6), 74.6 (95% CI, 36.3-167.8), 25.1 (95% CI, 11.2-55.0),20.0 (95% CI, 6.1-57.6), and 26.4 (95% CI, 4.4-11.1), respectively.

CONCLUSIONS

The highest relative risks were found for thyroid inhibitors, sulfamethoxazole-trimethoprim, sulfasalazine, clomipramine, and dipyrone combined with analgesics.

NSAIDs associated with increased risk of congestive heart failure in elderly patients taking diuretics

BACKGROUND

Both diuretics and nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used, in particular among the elderly. The use of NSAIDs may decrease the efficacy of diuretics and induce congestive heart failure (CHF) in patients treated with diuretics.

OBJECTIVE

To investigate the risk of CHF associated with combined use of diuretics and NSAIDs in patients older than 55 years.

METHODS

We conducted a study in a base cohort of 10,519 recipients of diuretics and NSAIDs identified in the PHARMO database during the period from 1986 through 1992. The incidence density of hospitalizations for CHF during exposure to both diuretics and NSAIDs (index) was compared with that during exposure to diuretics only (reference).

RESULTS

We found an overall increased risk of hospitalization for CHF during periods of concomitant use of diuretics and NSAIDs compared with use of diuretics only (crude relative risk, 2.2; 95% confidence interval, 1.7-2.9). After adjusting for cofactors including age, sex, history of hospitalization, and drug use, a 2-fold increased risk remained (relative risk, 1.8; 95% confidence interval, 1.4-2.4).

CONCLUSION

Use of NSAIDs in elderly patients taking diuretics is associated with a 2-fold increased risk of hospitalization for CHF, especially in those with existing serious CHF.

Application of the ATC/DDD methodology to monitor antibiotic drug use

In order to monitor the use of antibiotics, it is essential to have comprehensive data on drug consumption. The findings of drug utilisation studies can serve to describe the pattern of drug use in a particular population, to detect areas of concern, and to evaluate the impact of interventions taken to influence the use of drugs. In the present study, the Anatomical Therapeutical Chemical Classification/Defined Daily Doses (ATC/DDD) system developed by the World Health Organisation was evaluated. The system measures the amount of drug used independent of package size and sales price, which allows comparisons not only within an institution but also within a region, a country, or even internationally. Obviously, there can be no modifications of this system. To illustrate the method, the pattern of quinolone use in the general population, in long-term care facilities, and within a single institution was analysed. These drugs were widely used in long-term care facilities in the Nijmegen region of the Netherlands, accounting for about 30% of the antibiotics used in these settings, whereas in the general population as well as in the University Hospital Nijmegen, these drugs constitute only about 6% of the total antibiotics used. These differences are large enough to warrant closer analysis of patterns of antibiotic usage in different settings to identify the reasons for the use of quinolones and to identify measures that might be taken to rationalise the prescription of these drugs.

Dispensing epilepsy medication: a method of determining the frequency of symptomatic individuals with seizures

We estimated the prevalence and incidence of epilepsy in The Netherlands using drug-dispensing information from the PHARMO database, containing medication histories of nearly 300,000 individuals. An algorithm based on antiepileptic drug prescription records was used to identify patients with epilepsy requiring medication for seizure control. The algorithm was validated by comparing positive algorithm identifications to medical diagnoses from general practitioners and hospital records. In 1990-1991, the algorithm revealed 1158 patients with "certain" epilepsy, and 451 patients with "probable" epilepsy. Epilepsy was present in 93% of patients on polytherapy, and 58% on monotherapy. Clonazepam monotherapy was non-specific for epilepsy. The use of carbamazepine monotherapy for epilepsy was age-dependent. After correcting the algorithm for these drugs, and standardizing to the Dutch population, the point prevalence of epilepsy was 4.8/1000 (95% CI: 4.5-5.0). The incidence rate was 0.72/1000 person-years (95% CI: 0.65-0.79). Using drug-dispensing data for epilepsy medication, it is possible to make valid estimations of the number of epilepsy patients requiring drug therapy.

Neuro-psychiatric effects of antimalarials

OBJECTIVE

To study the neuro-psychiatric adverse effects of antimalarial drugs.

SETTING

Persons who visited a Travel Clinic in Rotterdam over a period of 3 months.

DESIGN

Prospective cohort study on 394 persons taking mefloquine, 493 persons taking proguanil and 340 persons not taking antimalarial drugs who visited Africa, South America, Asia, or the Middle East.

METHODS

All persons received a structured questionnaire within 14 days of their return to the Netherlands. The questionnaire consisted of questions regarding use of alcohol, smoking, general health, medical history, tropical diseases during the trip, and other medicines, and contained an extensive list of general complaints regarding all body systems at four levels of severity. A modified and validated version of the Profile of Mood States was included.

RESULTS

In the study period, 2541 persons visited the Travel Clinic, of whom 1791 (70%) were both eligible and willing to co-operate. Of these 1791, data were obtained from 1501 (84%). Insomnia was most frequently encountered in users of mefloquine and mouth ulcers in proguanil users. After adjustment for gender, age, destination, and alcohol use, the relative risk for insomnia to mefloquine versus non-users of antimalarials was 1.6, and the excess risk was 6 per 100 users over an average period of 2 months. There were no significant differences between groups in depression, anxiety, agitation, and confusion. Stratification by gender demonstrated that insomnia was more common in women on mefloquine, but not in men. Also, women more frequently mentioned palpitations as an adverse event. After adjustment for age, destination, and alcohol use in women, the relative risks for insomnia and palpitations to mefloquine versus non-use of antimalarials were 2.4, and 22.5, respectively. When travellers were specifically asked for the adverse reactions they had experienced, anxiety, vertigo, agitation, and nightmares were significantly more frequently mentioned by mefloquine users.

CONCLUSION

Insomnia was more commonly encountered during use of mefloquine than proguanil or during non-use of antimalarials.

Use of antiepileptic drugs in a community-dwelling Dutch population

We compared the treatment policy for patients with epilepsy in six Dutch cities, comprising 302, 149 inhabitants, with the treatment policies of a secondary referral center (a university hospital) and tertiary referral centers (outpatient departments of epilepsy centers). By comparing the prevalence of individuals receiving antiepileptic drugs in the six cities with the epidemiologic data for epilepsy in Rochester, Minnesota, we concluded that prescription data offer a suitable means by which to estimate the prevalence of epilepsy in a community. To compare prescriptions in cases of polytherapy, we normalized data by using defined daily doses published by the WHO Collaborating Center for Drugs Statistics Methodology and the Nordic Council on Medicines and concluded that the defined daily doses of antiepileptic drugs should be further elaborated. There is a need to obtain complete dose-response curves of equivalent antiepileptic drugs in humans. The trend of drugs use found in the six cities, the university hospital, and the epilepsy centers is, however, in accord with the expectations regarding primary, secondary, and tertiary referral centers.

Current use of thiazide diuretics and prevention of femur fractures

A case control study of a defined population from The Netherlands was performed to evaluate the risk of femur fractures associated with the use of thiazide diuretics. Included were 386 patients hospitalized for femur fractures between 1986 and 1990 who were residents and 45 years of age and older. Per case, one age-, sex-, pharmacy-, and general practitioner-matched control was chosen from the general population. Drug use was ascertained from computerized pharmacy records. The adjusted odds ratio of current use of thiazide diuretics was 0.5 (95% confidence interval, 0.3-0.9). The protective effect of thiazide diuretics was greatest for use of 1 year or longer at relatively high doses of thiazides (odds ratio, 0.3; 95% confidence interval, 0.1-0.9). We also found that patients who discontinued thiazide use longer than 2 months were not protected against femur fractures. These results support the hypothesis that use of thiazide diuretics protects against femur fractures.

[Reasons to report or not report side effects of drugs to the national monitoring system in the Netherlands]

OBJECTIVE

To assess the awareness of medical practitioners in the Netherlands regarding the national voluntary reporting scheme for adverse reactions to drugs, and the reasons for non-reporting.

DESIGN

Questionnaire.

SETTING

Netherlands Centre for Monitoring of Adverse Reactions to Drugs.

METHOD

A questionnaire was sent to a random sample of 500 practitioners aged under 65 in the database of the Dutch Inspectorate for Health Care.

RESULTS

Of the 500 questionnaires 265 (53%) were returned and completely filled in. Sixty-seven (25%) practitioners had reported a suspected adverse reaction on one or several occasions during their practising career; 229 (86%) would report a serious adverse reaction, 190 (72%) an unknown one, 185 (70%) an adverse reaction to a new product, and 83 (31%) a proven adverse reaction. Almost 20% said they had had difficulties reporting because they could not find the telephone number or reporting forms. Forty practitioners (15%) claimed that they were too busy to report adverse reactions. Almost all practitioners (94%) were aware of the fact that the reporting scheme serves the early detection of unknown adverse reactions.

Asthma medications and disease exacerbations: an epidemiological study as a method for asthma surveillance

Recent experimental and epidemiological studies have suggested that outcomes of asthma are significantly influenced by treatment patterns. This study was conducted in order to investigate the links between treatment patterns in asthmatics and occurrence of disease exacerbations. We performed a nested case-control study in a cohort of 680 asthmatics identified between 1986 and 1991 in a drug dispensing database. After validation in a pilot study, the intermittent use of oral corticosteroids was used as a proxy for asthma exacerbations. Cases with an exacerbation (n=133) were pair-wise matched with controls. The type of medications used for the usual treatment of asthma were examined in relation to the risk of asthma exacerbation. The use of oral xanthines and inhaled fenoterol but not of inhaled salbutamol, corticosteroids, cromoglycate and ipratropium bromide was associated with an increased probability of asthma exacerbation. Within the cohort, the proportion of subjects dispensed inhaled corticosteroids rose from 12 to 27% between 1986 and 1991. The proportion of subjects using inhaled bronchodilators without inhaled corticosteroids also decreased over this period of time. The identification of markers of asthma exacerbations made it possible to link the probability of adverse outcome risk for such exacerbations with treatment patterns. This method could be useful in further development of asthma surveillance using drug dispensing databases.

Benzodiazepines and the risk of falling leading to femur fractures. Dosage more important than elimination half-life

BACKGROUND

In the past decade, the use of benzodiazepines has been identified as a major independent risk factor for accidental falls.

OBJECTIVE

To study the role of dosing, timing, elimination half-life, and type of benzodiazepine in relation to the occurrence of accidental falls leading to hospitalization for femur fractures.

METHODS

A 1:3 age-, sex-, and pharmacy-matched case-control study was performed using data from a Dutch record linkage system (PHARMO) (N = 300,000). Cases included 493 patients (55 years and older), newly admitted to the hospital for a femur fracture resulting from an accidental fall (between 1986 and 1992). Relative risk estimates were calculated using conditional logistic regression analyses to control for the potential confounding effects of concomitant drug use and presence of a wide range of underlying diseases.

RESULTS

Falls were significantly associated with current use of benzodiazepines (odds ratio, 1.6; 95% confidence interval, 1.2 to 2.1) and in particular with short half-life benzodiazepines (odds ratio, 1.5; 95% confidence interval, 1.1 to 2.0), sudden dose increases (odds ratio, 3.4; 95% confidence interval, 1.0 to 11.5), and concomitant use of several benzodiazepines (odds ratio, 2.5; 95% confidence interval, 1.3 to 4.9). A strong dose-response relationship (P < .0001) and dose-response relations among users of either short or long half-life benzodiazepines suggests that these increased risks are explained primarily by dose.

CONCLUSIONS

Benzodiazepines are a major, independent risk factor for falls leading to femur fractures, and the increased risk is probably explained by prescribing too-high doses to the elderly.

Bromocriptine and suppression of postpartum lactation. The incidence of adverse cardiovascular effects in women of child-bearing age

The use of bromocriptine for the suppression of postpartum lactation drew widespread attention to a potentially increased risk for cardiovascular and cerebrovascular adverse effects. To estimate the incidence of these events a follow-up study was performed among 2,130 women of 15-44 years of age who were treated with a course of bromocriptine in 1990-1992. None of these women were admitted to the hospital for cardiovascular or cerebrovascular events. However, the incidence of pregnancy hypertension and the use of cardiovascular drugs increased considerably in the last 2 months before delivery. Therefore, cardiovascular or cerebrovascular events can probably be explained by pre-existing morbidity rather than by the use of bromocriptine. We estimated, using a 'worst-case' analysis, that fewer than 2 Dutch women each year would develop serious cardiovascular or cerebrovascular events.

Hypoglycaemia associated with use of inhibitors of angiotensin converting enzyme

The use of angiotensin-converting-enzyme (ACE) inhibitors has been associated with increased insulin sensitivity in diabetic patients. Although such an effect could be beneficial in the treatment of hypertension or congestive heart failure in diabetic patients, it might also precipitate severe hypoglycaemia. To test this hypothesis we carried out a nested case-control study, using data in the Dutch PHARMO system (1986-92), among diabetic patients treated with insulin or with oral antidiabetic drugs, who were admitted to hospital with hypoglycaemia. We identified 94 patients who had been admitted with hypoglycaemia and selected 654 controls from the same cohort. With adjustment for a wide range of potential confounding factors, hypoglycaemia was significantly associated with current use of ACE inhibitors (odds ratio 2.8 [95% CI 1.4-5.7]). Both among users of insulin and among users of oral antidiabetic drugs, use of ACE inhibitors was significantly associated with an increased risk of hospital admission for hypoglycaemia (2.8 [1.2-6.4] and 4.1 [1.4-12.2], respectively). Although ACE inhibitors have several advantages over other antihypertensive drugs in diabetes, the risk of hypoglycaemia should be taken into account. Further investigation of the mechanism is needed since as many as 13.8% of all hospital admissions for hypoglycaemia might be attributable to use of ACE inhibitors.

A rapid method to estimate the incidence rate and prevalence of insulin-dependent diabetes mellitus in children 0-19 years of age

OBJECTIVE

To trace new cases of insulin-dependent diabetes mellitus (IDDM) on an ongoing basis and to estimate the incidence rate and prevalence of IDDM in children 0-19 years of age.

RESEARCH DESIGN AND METHODS

The estimation of the prevalence and incidence rate of IDDM was based on, respectively, the prevalence and the rate of new users of insulin. The data were obtained from pharmacy, patient-based, drug dispensing histories in a well-defined population encompassing 257,113 individuals in the Netherlands.

RESULTS

The IDDM incidence rate was estimated at 11.5 (CI95 6.6-17.8) per 100,000 person years in 1989-1990 in children 0-19 years of age. The prevalence was estimated at 11.0 (CI95 8.6-13.4) per 10,000 children 0-19 years of age.

DISCUSSION

The incidence rate is comparable to that found in a large, national survey among all paediatricians and internists in the Netherlands. The method offers ongoing monitoring of the incidence and prevalence of IDDM in children, 0-19 years of age, against low costs. The method is suitable for rapid and cost-efficient recruitment of cohorts of incident IDDM patients, which fosters research to identify and quantify the attribution of different types of aetiologic and prognostic factors of IDDM.

[Skin reactions attributed to the use of bromhexine]

Since 1972, the Netherlands Centre for Monitoring of Adverse Reactions to Drugs has received 22 reports of skin reactions attributed to use of bromhexine. The reports concerned II men and II women. The ages ranged between 5 months and 88 years. The skin reactions occurred within one to 30 days after starting the use of bromhexine. Most skin reactions consisted of generalised urticaria. Other reports concerned once an angioedema and once an anaphylactic reaction. Most patients recovered completely after cessation of bromhexine without further treatment.

Public health problems and the rapid estimation of the size of the population at risk. Torsades de pointes and the use of terfenadine and astemizole in The Netherlands

Recently, the use of astemizole and terfenadine, both non-sedating H1-antihistamines, caused considerable concern. Several case reports suggested an association of both drugs with an increased risk of torsades de pointes, a special form of ventricular tachycardia. The increased risk of both H1-antihistamines was associated with exposure to supratherapeutic doses; for terfenadine the risk was also associated with concomitant exposure to the cytochrome P-450 inhibitors ketoconazole, erythromycin and cimetidine. To predict the size of the population that runs the risk of developing this potentially fatal adverse reaction in the Netherlands, the prevalence of prescribing supratherapeutic doses and the concomitant exposure to terfenadine and cytochrome P-450 inhibitors was studied. Data were obtained from the PHARMO data base in 1990, a pharmacy-based record linkage system encompassing a catchment population of 300,000 individuals. The results of the study showed that the prescribing of supratherapeutic doses and the concomitant exposure to terfenadine and cytochrome P-450 inhibitors was low. Furthermore, the results of a sensitivity analysis showed that the risk of fatal torsades de pointes has to be as high as 1 in 10,000 to cause one death in the Netherlands in one year.

A population based case-cohort study of drug-induced anaphylaxis

1. In order to determine the risk of anaphylaxis as an adverse reaction to drugs, a case-cohort study was performed. Cases consisted of all admissions in 1987 and 1988 to all Dutch hospitals with anaphylaxis as the principal diagnosis, and a random sample of admissions with related symptoms. Hospital discharge summaries were classified according to probability to anaphylaxis by a blinded Audit Committee. Of admissions classified as probable or possible anaphylaxis, the causative agent was assessed. The reference cohort consisted of all persons in the catchment area of a sample of pharmacies in The Netherlands, in the period between January 1, 1987 and December 31, 1988. 2. Out of 934 admissions, discharge summaries on 811 admissions were received, of which 727 contained enough clinical details. Out of 727, 391 were classified as probable or possible anaphylaxis. In 336 of these 391, anaphylaxis was reason for admission. This group consisted of 158 men and 178 women. Drug-induced anaphylaxis occurred in 107 patients. 3. Drug-induced anaphylaxis was most frequently caused by penicillins, analgesics and non-steroidal antiinflammatory drugs (NSAID) with the highest point estimate of the risk relative to all other drugs of 10.7, 6.9 and 3.7 respectively. 4. In the cases of probable anaphylaxis, the risk of anaphylaxis to glafenine relative to all other drugs was 167.7 in 1987 (95%-CI: 63.0-446.4) and 128.6 in 1988 (95%-CI: 50.4-328.5), to amoxycillin 15.2 in 1987 (95%-CI: 5.0-46.0) and 4.4 in 1988 (95%-CI: 1.03-18.9) and to diclofenac 6.1 in 1988 (95%-CI: 1.4-26.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmaco-morbidity linkage: a feasibility study comparing morbidity in two pharmacy based exposure cohorts

STUDY OBJECTIVES

The aims were (1) to compare discharge diagnoses and concurrent medication in a pharmacy based cohort of users of H2 receptor antagonists to those in a population of users of other drugs in the same period, who did not use H2 receptor antagonists; (2) to compare these results to those of a similar study performed with the Tayside record linkage scheme.

DESIGN AND SETTING

The study was a retrospective cohort study. The morbidity data from the only hospital in one medium sized city (62,000 inhabitants) were linked to the dispensing data of all five community pharmacies on an individual basis (April 1, 1986-December 31, 1989). In the absence of a unique patient identification number, data from pharmacies and hospital were linked by the combination of date of birth, gender, and general practitioner code. For every user of H2 receptor antagonists two controls were obtained from all patients who had not used these drugs, and matched for age (within 5 years), gender, and general practitioner. All discharge diagnoses which followed this first prescription up to December 31, 1989, in a patient in the index cohort, and during the same period in his or her matched controls, were included in the study.

MAIN RESULTS

In the index cohort (n = 2174) 341 persons were admitted (526 admissions) as against 398 persons (527 admissions) in the control cohort (n = 4348). There was increased morbidity in the index cohort, especially concerning the gastrointestinal system (peptic ulcers and malignancies, abdominal pain, gastrointestinal haemorrhage), but also concerning the musculoskeletal, respiratory, and circulatory systems. The morbidity in the last three groups corresponded with drugs used concomitantly by patients in the index cohort, so it was probably not causally related to the intake of H2 receptor antagonists but was rather an indicator of higher levels of morbidity in the index cohort.

CONCLUSIONS

The figures were grossly comparable to those of the Tayside record linkage scheme. Probabilistic linking with the patient characteristics of gender, date of birth, and general practitioner code can facilitate the undertaking of postmarketing surveillance studies.

Ad hoc tracing of a cohort of patients exposed to acitretine (Neotigason) on a nation-wide scale

Etretinate has been detected in the blood of women taking acitretine. Because of the proven teratogenic effects of etretinate it was decided to try to trace all users of acitretine in The Netherlands via all drug dispensing outlets (1450 community pharmacies, 95 hospital pharmacies and 636 general practitioners). A request for information on the date of birth, sex, type of prescriber, and the number of capsules dispensed yielded a response rate of 87%. In 61% of all the responding dispensing outlets a prescription for acitretine had been filled. Of these 1153 outlets, 40% had dispensed acitretine to one patient and 52% had dispensed it to 2-5 patients. The 2717 patients comprised 1500 men (55%) and 1217 women, with mean ages of 48 and 53 y, respectively. As against 45% of all the male users, 31% of all the women were in the child-bearing age (15-45 y). The average numbers of dispensed capsules was 167 to users of 10 mg capsules, and 107 to users of the 25 mg capsules. In more than 80% of cases acitretine had been prescribed by dermatologists. Because the large majority of inhabitants in The Netherlands use one community pharmacy, and because most of them have automated records, it is possible to trace a cohort of users quickly and almost completely. Because most large-scale problems with adverse reactions are discovered within the first 2 years of marketing, at a time when exposure and morbidity registries are still collecting information, ad hoc formation of a cohort in this way may be a useful resource for postmarketing surveillance.

[Acitretin; an example of ad-hoc tracing of users in acute problems with drugs]

Recently etretinate was demonstrated in the blood of women on acitretin. Because of the proven teratogenic effects of etretinate we tried to trace all users of acitretin in the Netherlands via all drug dispensing outlets (1450 community pharmacies, 95 hospital pharmacies and 636 general practitioners). A request for information as regards date of birth, sex, type of prescriber, and number of dispensed capsules was followed by a response rate of 87%. In 61% of all responding outlets a prescription of acitretin had been filled. Of these 1153 outlets 40% had dispensed the drug to one user, whereas 52% had dispensed acitretin to 2-5 patients. The 2717 patients consisted of 1500 men (55%) and 1217 women with mean ages of 48 and 53 years, respectively. Of the women 31% were in the age-group of 15-45 years and of the male users, 45% (p less than 0.0001), whereas in other age groups there was no difference. In 80% of cases acitretin had been prescribed by dermatologists. This study demonstrated that it is possible to trace a cohort of users quickly and almost completely. As most large-scale problems with adverse reactions are discovered in the first 2 years of marketing when exposure and morbidity registries are still collecting information, ad hoc cohort formation may be a useful resource for postmarketing surveillance.

[Pharmaco-morbidity linking: a pilot study of its technical possibilities in The Netherlands]

The feasibility has been studied of linking pharmacy-based dispensing data and hospital-based morbidity data by using as a linkage key a combination of gender and birth date of the patient and of his general practitioner (GP) code. Firstly, the records of one pharmacy (14,686 patients) and those of one hospital (8475 admissions in 1987) were linked on the basis of date of birth and gender. This resulted in 3,715 matching record pairs. To a random sample of 1,713 of these pairs the GP code was added. Subsequently these pairs were validated by reference to the original medical and pharmaceutical records with a procedure that guaranteed that only the name and address of the patients could be compared without having access to the clinical or pharmaceutical record of an individual. We were able to link records with a sensitivity of 91.4% (95%-confidence interval: 88.8-94.0) and a specificity of 96.0% (95%-confidence interval: 94.5-97.5). In conclusion, probabilistic linkage of pharmaceutical and medical data with the combination of gender, date of birth and GP code facilitates successful record linkage.