Temporal trends and drug exposures in pulmonary hypertension: an American experience

BACKGROUND

Reports have linked anorexigen intake to an increased risk of pulmonary arterial hypertension (PAH). With the rise in anorexigen use in the latter half of the last decade, we established a surveillance network within the United States to monitor temporal trends in the number of reported cases of PAH. We also studied whether use of anorexigens and other drugs differed among patients with pulmonary hypertension of different etiologies.

METHODS

Newly diagnosed subjects (N = 1335) at 13 tertiary pulmonary hypertension centers were enrolled between January 1998 and June 2001. Patient-reported medication use was obtained by a telephone interview. Patients were classified as to the type of pulmonary hypertension. Poisson regression models were fitted to monthly case counts, and logistic regression methods were used to assess the association between type of pulmonary hypertension and medication use.

RESULTS

The average monthly number of reported cases of PAH and other categories of pulmonary hypertension did not change over the study period. Fenfluramine or dexfenfluramine use during the 5 years before the time of the interview was preferentially associated with PAH. Fenfluramine/dexfenfluramine use was particularly common in cases referred but found not to have pulmonary hypertension.

CONCLUSIONS

No epidemic of anorexigen-related PAH was evident during the study period. As persons who had taken fenfluramine or dexfenfluramine were particularly likely to be referred for evaluation of pulmonary hypertension, it is unlikely that the failure to detect an anorexigen-induced rise in primary pulmonary hypertension was because of underascertainment. The association between fenfluramine derivatives and PAH is consistent with the risk elevations previously reported.

Anorexigen-related cardiopulmonary toxicity

Three years after the withdrawal of fenfluramine and dexfenfluramine from the market, the magnitude and prevalence of their deleterious cardiopulmonary effects remain undetermined. The links between these anorexigens and valvular heart disease and primary pulmonary hypertension, however, are clearly established. Because some evidence indicates that the valvular lesions may regress with cessation of the drug, management guidelines are still in flux. Patient reassurance and close surveillance, including serial echocardiography in selected cases, are warranted.

[Pulmonary hypertension and obesity]

Obesity is a morbid condition with hemodynamic consequences affecting the systemic and pulmonary circulations leading to a risk of pulmonary hypertension. Data in the literature do not argue in favor of a direct relationship between pulmonary hypertension and obesity. These two conditions appear to be two distinct entities, the different co-morbidities observed in obesity favoring pulmonary hypertension. Certain co-morbidities, for instance use of anorexic agents, exhibit a clear relationship with pulmonary hypertension. There is also a possible relationship with left ventricular failure, hypoxemia, and other respiratory disorders (including obstructive sleep apnea), hypothyroidism, and thomboembolism.

Risk factors for pulmonary arterial hypertension

The present limitations in knowledge of the potential risk factors for PPH undoubtedly are attributable to the facts that PPH is a rare disease with an unknown pathogenesis and lacking large case series. Moreover, definite epidemiologic data are rare and ideally should be obtained from epidemiologic surveys such as large case-control studies. The increased incidence of the disease in young women, the familial cases, the association with autoimmune disorders, and the recent discovery that mutation of the PPH1 gene may not be restricted to familial PPH support the hypothesis that the development of pulmonary hypertension likely implies an individual susceptibility or predisposition, which is probably genetically determined. It is also now commonly believed that the development of pulmonary hypertension in some of these predisposed individuals could be hastened or precipitated by various expression factors (some of them yet unrecognized), such as ingestion of certain drugs or diets, portal hypertension, or HIV infection.

[Drug induced pulmonary hypertension]

Primary pulmonary hypertension (PPH) is a rare, often fatal disease that tends to occur with particular frequency in woman. The factors leading to its development remain enigmatic. A variety of toxins and drugs have been implicated in the pathogenesis of pulmonary hypertension (PH). In the 1960s, the medical community was first alerted to the problem of an epidemic of PH in association with a particular anorexic agent, aminorex. Recent reports have indicated that anorexic drugs may have causative roles in PH. The International Primary Pulmonary Hypertension Study (IPPHS) showed a strong association between PPH and the use of appetite suppressants. But the mechanism by which these anorectic drugs cause PH is unknown.

Anorectic drugs and pulmonary hypertension from the bedside to the bench

Anorectic drugs have been used for more than 30 years as an aid in weight reduction for obese persons. The use of aminorex, an amphetamine analog that increases norepinephrine levels in the central nervous system, led to an epidemic of primary pulmonary hypertension (PPH) in Europe in the late 1960s and early 1970s. The use of fenfluramine and later dexfenfluramine [drugs that inhibit 5-hydroxytryptamine (5-HT) release and reuptake and increases 5-HT and thus 5-HT secretion in the brain] was associated with a second epidemic of PPH. All of these drugs have been voluntarily withdrawn from the market. The pathogenesis of PPH in patients treated with these agents is uncertain, but recent evidence suggests that potassium channel abnormalities and vasoactive and proliferative properties of 5-HT may play a role. There is increasing experimental evidence suggesting that aminorex, fenfluramine and dexfenfluramine inhibit 4-aminopyridine-sensitive currents in potassium channels resulting in vasoconstriction in pulmonary resistance vessels and perhaps smooth muscle cell proliferation. 5-HT causes pulmonary artery vasoconstriction and smooth muscle cell proliferation. Its levels are known to be high in those with fenfluramine-induced PPH. However, a firm cause-and-effect relationship has not yet been established. One potentially beneficial effect of the epidemics of anorectic-related PPH is that it may have provided important insights into the causes of PPH unrelated to anorectic agents.

Recreational use of aminorex and pulmonary hypertension

Pulmonary hypertension has been associated with ingestion of the appetite suppressant aminorex. A similar compound, 4-methyl-aminorex (street names, "U-4-E-uh" [pronounced euphoria] or "ice"), is a "designer" drug with central stimulant activity. This drug was discovered on the property of three individuals with diagnoses of pulmonary hypertension. The association between "recreational" aminorex manufacture and ingestion and the development of pulmonary hypertension is described.

[Obesity: principles of drug therapy]

Obesity is a major global public health problem. In many instances, a combination of diet modification, increased physical activity and behavior therapy fail or are insufficient for sustained weight loss. In these situations, drug therapy may be helpful. However, drug treatment of obesity resulted in unexpected devastating events in recent years. In the late sixties, aminorex caused an epidemic of pulmonary hypertension with high mortality rates. Dexfenfluramine and phentermine were also associated with the development of pulmonary hypertension and with alarming reports of cardiac valvular abnormalities. Therefore, these drugs were withdrawn from the market. Newer drugs, like sibutramine, a serotonin and norepinephrine reuptake inhibitor, and orlistat, a specific lipase inhibitor, reduce body weight significantly compared to placebo. In combination with a hypocaloric diet, weight loss of three to ten kilos can be achieved. Pharmacotherapy is limited to patients with a body mass index greater than 30 kg/m2, if non-pharmacological treatment programs have failed. The drugs should be prescribed under strict medical surveillance only.

Delayed onset of pulmonary hypertension associated with an appetite suppressant, mazindol: a case report

The use of the appetite suppressant agents aminorex and fenfluramine derivatives has been reported as a risk factor for the development of pulmonary hypertension. A 29-year-old female developed pulmonary hypertension suspected to be due to an amphetamine-like appetite suppressant agent, mazindol ((+/-)-5-(p-chlorophenyl)-2,5-dihydro-3H-imidazo [2,1-a] isoindol-5-ol). She was admitted to Sapporo Medical University Hospital with dyspnea due to severe pulmonary hypertension. Twelve months prior to admission, she had taken mazindol continuously for a period of 10 weeks. As yet, her pulmonary hypertension has not completely improved. This is the first reported case of mazindol-associated pulmonary hypertension, which developed after a long latent interval, and it suggests that mazindol is also a risk factor for the development of pulmonary hypertension, making long-term follow-up necessary for patients taking this anorectic agent.

Monoclonal endothelial cells in appetite suppressant-associated pulmonary hypertension

Anorexigens such as aminorex fumarate and dexfenfluramine are associated with the development of severe pulmonary hypertension (PH), which clinically and histopathologically is considered indistinguishable from idiopathic or primary pulmonary hypertension (PPH). For the current study, we asked whether anorexigen-associated PH is characterized by monoclonal pulmonary endothelial cell proliferation (such as in PPH) or, alternatively, is associated with a polyclonal endothelial cell proliferation as found in secondary PH. Analysis of clonality by the human androgen receptor assay was performed in microdissected endothelial cells of plexiform lesions of two patients with anorexigen-associated PH. The four plexiform lesions of Patient 1 and the six of Patient 2 with anorexigen-associated PH exhibited a monoclonal expansion of pulmonary endothelial cells, with a mean clonality ratio of 0.03 +/- 0.01 SE. Our results indicate that appetite suppressant-associated PH is identical to PPH not only in clinical and histopathologic features but also, at a molecular level, in terms of the monoclonal nature of the endothelial cell proliferation. The anorexigens may accelerate the growth of pulmonary endothelial cells in patients with predisposition to develop PPH.

Aminorex, dexfenfluramine, and primary pulmonary hypertension

BACKGROUND

In the late 1960s, an epidemic of primary pulmonary hypertension (PPH) occurred in Europe shortly after the introduction of aminorex fumarate, a potent anorexigen. A recently published case-control study from Europe reported that use of other anorexigens (the most prevalent of which was dexfenfluramine) was also associated with an increased risk of PPH. This led to warnings of a repeat epidemic, especially after the introduction of dexfenfluramine on the North American market.

OBJECTIVE

To compare the epidemiologic associations of PPH with aminorex and dexfenfluramine, both with respect to strength of association (estimate of relative risk) and public health impact (etiologic fraction) and thus to assess the potential for a new epidemic of PPH.

METHODS

We constructed a "synthetic" case-control study for aminorex based on reported case series from Berne and Basel, Switzerland, and a random population sample from Hanover, Germany, and compared the results with those recently reported for dexfenfluramine. Control rates of exposure were used to estimate population exposure prevalences and, hence, etiologic fractions.

RESULTS

The estimated odds ratio (and 95% confidence interval) for the association between PPH and any exposure to aminorex was 97.8 (78.9-121.3), with a corresponding etiologic fraction of 77%. The corresponding figures for dexfenfluramine were 3.7 (1.9-7.2) and 17%, respectively.

CONCLUSION

The strong association between aminorex and PPH probably led to a 5-fold increase in PPH incidence, and thus a very noticeable epidemic. The association with dexfenfluramine would result in an increase in incidence of only 20%. Based on the available evidence, a repeat PPH epidemic seems unlikely.

The effect of anticoagulant therapy in primary and anorectic drug-induced pulmonary hypertension

In a retrospective study, we tested the hypothesis that anticoagulant therapy with warfarin sodium (Coumadin) has a beneficial influence on the long-term prognosis in patients with primary pulmonary hypertension (PPH) and aminorex-induced plexogenic pulmonary hypertension. The study included a total of 173 patients from two European cities. One hundred four of these patients took the anorectic drug aminorex (Menocil), which was available in some European countries almost 30 years ago; 69 patients had pulmonary hypertension of unexplained etiology, ie, PPH. Fifty-six of the 104 aminorex-treated patients and 24 patients in the PPH group received warfarin after diagnosis was established. For analysis, patients were divided into four groups according to their history of aminorex intake and anticoagulant therapy. Survival time, changes in hemodynamics (pulmonary arterial pressure), and improvement in quality of life (scored by the New York Heart Association [NYHA] classification) were compared and analyzed. We found that aminorex-treated patients had a better long-term prognosis than those with PPH (7.5 vs 3.9 years; p < or = 0.001). The best mean survival time of 8.3 years was found in anticoagulated aminorex-treated patients, compared to 6.1 years in nonanticoagulated aminorex-treated patients. Moreover, aminorex-treated patients who received anticoagulant therapy soon after the onset of symptoms showed significantly better prognosis (10.9 years) than those who commenced treatment 2 years thereafter (5.9 years) (p < or = 0.05). In patients with PPH, systolic pulmonary pressure was shown to influence survival time significantly (p < or = 0.0005); however, this correlation was not found in aminorex-treated patients. An improvement of symptoms like dyspnea on exertion was seen in 44.8% of the anticoagulated aminorex-treated patients, while deterioration was evident in 72.2% of the nonanticoagulated aminorex-treated patients. In conclusion, our study has shown that anticoagulant therapy had a positive influence on long-term survival and a significant improvement in quality of life in patients with PPH, in particular in patients with a history of anorectic drug intake.

[Aminorex-induced, plexogenic pulmonary arteriopathy: 25 years later!]

The purpose of this study was to examine the influence of treatment on long-term prognosis of patients with aminorex-induced plexogenic pulmonary hypertension. The study included 104 patients (13 males, 91 females) with an aminorex (menocil) intake between 1966 and 1968. All patients were treated with digitalis and diuretics, 52% received an anticoagulant medication with warfarin after pulmonary hypertension was diagnosed. During follow-up, a second right-heart catheterization was performed in 37 patients with a mean interval of 5 years. The longest mean survival time, 8.3 years, was found in patients treated with anticoagulant medication, compared to the 6.1 years found in the non-anticoagulated aminorex patients. Also, in the 5- and 10-years survival rate, patients with an anticoagulant therapy have shown better results (62.9 vs. 38% and 39 vs. 20%, respectively). Patients who received anticoagulant therapy soon after the onset of symptoms showed a better mean survival (10.9 years) than those who commenced treatment more than 1 year thereafter (mean survival 5.9 years). In 57% of the patients who had a second right-heart catheterization a decrease of pulmonary pressures could be diagnosed. Two-thirds of these patients with pulmonary pressure decrease were under anticoagulant therapy. An improvement in the NYHA-classification was seen in 44.8% of the patients treated with warfarin, in comparison to 22.2% of those who did not receive anticoagulant therapy. Although this study is retrospective, it shows a positive influence of anticoagulant therapy on survival in patients with a history of anorectic drug intake.

Specificity of pulmonary vascular lesions in primary pulmonary hypertension. A reappraisal

The type and distribution of pulmonary vascular lesions in 23 cases of primary pulmonary hypertension were reviewed. 15 cases were classified as plexogenic arteriopathy. The remaining cases displayed thromboembolic lesions. All cases showed a predominance of eccentric intimal lesions. In the plexogenic group, mixed concentric and eccentric intimal fibrosis coexisted. Therefore, in the present study, we propose an objective descriptive approach to the diagnosis of hypertensive pulmonary vascular disease, to correlate morphology and function.

[Prolonged survey of cases of pulmonary hypertension in relation to consumption of aminorex. Histological, quantitative and morphometric study of 9 cases]

The lesions of pulmonary muscular arteries of 9 female patients who died of pulmonary hypertensive disease between 9 and 17 years after intake of an anorexigenic drug, aminorex fumarate, have been examined by various methods (light microscopy, numeration of lesions, morphometry). The numeration of lesions showed the predominance of fibrotic and dilatation lesions, but also the presence of active lesions (intimal hyperplasia, plexiform lesions). Morphometry revealed an increase in mean thickness of the media, compared to that of the arteries of controls or those of a previous series, and a reduction in mean vascular volume. The existence of sclerotic lesions and reduction of vascular volume may explain the persistence of pulmonary hypertension, which fresh lesions helped to aggravate. It seems likely that functional and morphologic modifications due to the action of the drug had become self-perpetuating and may finally have induced the fatal outcome in these patients many years after intake of the slimming pill.

Development of pulmonary aneurysm in primary pulmonary hypertension: a case report

Selected cases of severe primary pulmonary arterial hypertension and associated pulmonary vascular disease have been related to the oral ingestion of aminorex fumarate, an anorexigen obviously responsible for an epidemic of primary pulmonary hypertension in Western Europe between 1967 and 1970. This report describes a fifteen year follow-up of a female patient with aminorex fumarate related pulmonary hypertension and the uncommon finding of the formation of an excessive fusiform pulmonary trunk aneurysm in the late stage of the disease process. The progressive clinical course was followed by serial chest x-ray films and repeat right heart catheterization. The diagnosis of a main stem pulmonary artery aneurysm was noninvasively established by two-dimensional echocardiography and confirmed by contrast-enhanced computed tomography and radionuclide blood pool imaging. The patient is alive, thus no histologic correlate of this entity is available at present.

Primary pulmonary hypertension. An analysis of 28 cases and a review of the literature

The diverse potential etiologies and varying degrees of severity at the time of presentation suggest that primary pulmonary hypertension is a spectrum of disease states, all of which share the hemodynamic and pathologic correlates of pulmonary hypertension without a demonstrable cause. The course is variable, but manifestations of a low cardiac output or right ventricular failure imply a poor prognosis; the median survival is 2 to 3 years from the time of diagnosis. Although several systemic vasodilators have been demonstrated to improve pulmonary hemodynamics and ameliorate symptoms in some cases, these drugs may produce undesirable adverse effects, including death, in unresponsive patients. Additionally, the impact of vasodilator therapy on mortality from PPH has not been assessed. Combined heart-lung transplantation should be considered in patients who are unresponsive to vasodilators and who manifest the indicators of a poor prognosis.

Polymorphic debrisoquine and mephenytoin hydroxylation in patients with pulmonary hypertension of vascular origin after aminorex fumarate

During the period 1967 to 1971 an increase in the incidence of pulmonary hypertension of vascular origin (PHVO) was observed in Austria, Federal Republic of Germany, and Switzerland. Most patients had been given aminorex fumarate and a possible link was suspected. We therefore investigated the possibility of genetically-determined drug hydroxylation deficiencies (debrisoquine or mephenytoin type) in these patients as an explanation for the development of PHVO. Seventeen patients took 10 mg debrisoquine and 100 mg mephenytoin orally. Sixteen PHVO patients were classified as extensive metabolizers of debrisoquine with logarithmic metabolic ratios of -0.35 +/- 0.11 (mean +/- SEM), whereas one patient was a poor metabolizer with a logarithmic metabolic ratio of 1.82. For the mephenytoin hydroxylation sixteen patients with PHVO were extensive metabolizers, with logarithmic hydroxylation indices of 0.27 +/- 0.05. One poor metabolizer of mephenytoin had a logarithmic hydroxylation index of 1.59. Deficient hydroxylation of debrisoquine and mephenytoin was found in two different patients. The prevalence of poor metabolizers among patients with PHVO after aminorex fumarate was therefore approximately 9% for both debrisoquine and mephenytoin. This corresponds closely to the data of our reference population study where genetic debrisoquine and mephenytoin hydroxylation deficiencies occurred independently, with a prevalence of 10% and 5% respectively. Thus, the normal prevalence of extensive drug hydroxylation phenotypes in patients with PHVO is not consistent with the hypothesis that the development of PHVO after aminorex fumarate might be related to a pharmacogenetically determined impairment of polymorphic drug oxidation.

[Chronic pulmonary hypertension of vascular origin, plexogenic pulmonary arteriopathy and the appetite depressant aminorex: addenda to an epidemic]

An epidemic of chronic pulmonary hypertension occurred in Austria, the Federal Republic of Germany, and Switzerland, starting in 1967, peaking in 1968/69, and disappearing after 1972. The mechanism leading to pulmonary hypertension was precapillary vascular obstruction due to plexogenic pulmonary arteriopathy. There was a close geographic and temporal relationship between the epidemic and the marketing and intake of the appetite-depressing drug aminorex fumarate (Menocil). The epidemic was limited to the three above countries where aminorex had been on sale. In the individual patient the symptoms, usually dyspnea, angina pectoris and syncope on exertion, used to follow the beginning of the drug in-take after one year. A similar phase shift could be observed between marketing of the anoretic and the incidence of patients with chronic pulmonary hypertension of vascular origin. The new disease is compared with known forms of pulmonary vascular obstruction. It cannot be distinguished from classical primary pulmonary hypertension or from recurrent silent pulmonary thromboembolism on either clinical or functional grounds; it has plexogenic pulmonary arteriography in common with the former. The prognosis, however, is different: survival is considerably longer in patients with aminorex-associated pulmonary hypertension, and a marked decrease in the pulmonary vascular obstruction after 10 years is no exception. Considering the closeness of the various associations between the event (i.e. the epidemic) and its suspected cause (the anoretic aminorex) from the viewpoint of epidemiological, pharmacological, morphological and prognostic findings and considerations, there is little doubt that aminorex, besides other partly known and partly unknown factors, can in fact favour or cause the development of plexogenic pulmonary arteriography and pulmonary hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

[Long-term course of primary vascular pulmonary hypertension with and without intake of appetite depressants]

1. The long-term follow-up of 22 patients with anorectic drug intake (aminorex fumarate) (AS) and PVPH is compared to 38 patients with PVPH of unknown etiology. 2. The 10-year cumulative survival rate is significantly higher for the AF-positive group (54 +/- 11%) than for the AF-negative patients (15 +/- 6%). 3. In terms of the hemodynamic parameters at the time of diagnosis, there were no differences between the two patient groups. 4. Hemodynamic serial controls in the AF-positive group often show a decrease in pulmonary pressure at rest, in contrast to the AF-negative group. However, in all but one of the patients with a pressure drop at rest there is a considerable increase in pulmonary pressure during exercise. 5. In neither group any correlation is to be found between pulmonary pressure and survival time.

[Modification of psychosocial adjustment by terminal disease]

Psychosocial adaption during or after somatic illness is relatively little studied--quite in difference to the better known psychosocial predictors of somatic illness. This study is concerned with a group of 31 female patients who suffered from a terminal vascular disease (primary vascular pulmonary hypertension)--an iatrogenic disease which with high probability is the consequence of a drug for weight reducing (Menocil), prescribed by their family doctors to these moderate overweight middle aged women. Psychosocial adaptions was assessed on a 5-point-scale, including the following dimensions: work-situation, socio-economic conditions, family adaption, social activities. Psychosocial adaption before illness was very good (just 10% below maximal values). Two or three years after illness started, however, there was a highly significant drop in all dimensions (most significant in "work" and "social activities"). To some extent success or failure of psychosocial adaption had a predictive power for the terminal course of this illness. Possible interaction between course of illness and psychosocial adaption is discussed and illustrated. There was also a significant correlation between psychosocial adaption and defense-processes.

Pulmonary hypertension, "plexogenic pulmonary arteriopathy" and the appetite depressant drug aminorex: post or propter?

An epidemic of chronic pulmonary hypertension of vascular origin (CPHVO) has occurred in Austria, the Federal Republic of Germany, and Switzerland. The epidemic started in 1967 and reached its peak in 1968 and 1969. Since 1972, the prevalence of patients with CPHVO among individuals investigated by cardiac catheterization is again as low as in the pre-epidemic years. In Bern the prevalence of CPHVO during the peak of the epidemic was 20 times higher than during the 12-year period preceding the epidemic. The clinical, physical, electrocardiographic, radiologic, haemodynamic and respiratory findings of the patients observed in Bern (n = 102) are summarized. There has been a mortality between 12 and 20% at the time of the epidemic. Most patients observed for the first time during the epidemic have remained severely disabled over the years. A minute fraction seems to have recovered. There is a close geographic as well as temporal relation of the epidemic to the marketing and intake of the appetite depressing drug aminorex fumarate (Menocil). Acute administration of aminorex leads to a transient rise of the pulmonary artery pressure and vascular resistance in a number of animal species. It has not been possible to produce sustained precapillary pulmonary hypertension and chronic cor pulmonale vasculare under the conditions of chronic administration of the drug in the species tested. Morphologic examination of lung biopsy and autopsy material of patients who have died from CPHVO after the intake of aminorex reveals the presence of "plexogenic pulmonary arteriopathy". The vascular lesions are identical with those observed in pulmonary hypertension due to large congenital left-to-right shunts. In balancing the pros and cons, it appears that the arguments in favour of a cause-effect relationship between aminorex and pulmonary hypertension, which are derived from epidemiological evidence, outweigh the results of "negative" animal experiments. A "propter" in the title of this paper, therefore, seems to be more appropriate than a post".

How study of geographic epidemiology of disease can help in detection of adverse drug reactions

The geographic epidemiology of adverse drug reactions can often help in their recognition and in pinpointing the responsible drug. Since different countries often introduce new drugs at varying periods of time and they achieve varying degrees of popularity and use, this information may sometimes aid the epidemiologist in the search for the etiology of unwanted drug effects. Some examples where geography helped unravel the story behind certain adverse drug reactions are presented.

[Two-year peroral administration of aminorex in the dog. 2]

In an attempt to develop an experimental model of pulmonary hypertension, five mongrel dogs were treated with 1 mg/kg p. o. and five with 1.5 mg/kg p. o. of Aminorex base five days a week for two years. A control group was given empty capsules by months. The following effects of treatment with Aminorex were noted: 1. Anorexia and central stimulation, 2. Natriuresis, 3. an increase in respiration rate, heart rate and body temperature, 4. a tendency towards usually compensated metabolic acidosis, 5. an increase in pulmonary arterial pressure, total pulmonary resistance and right ventricular work, and, in the group given the higher dose, a slight increase in mean aortic pressure and peripheral resistance. 6. Only slight histopathological changes were detectable, e.g.: perivascular oedema; increase in the number of muscle arteries, occasionally with hypertrophy of the tunica media and slight, focal fibro-elastoid thickening of the intima in some elastic arteries. These changes were present in about 60% of the treated dogs. Only one dog that died after 91 weeks' treatment also showed moderate, focal phlebosclerosis of large pulmonary veins and focal, fibro-elastoid thickening in the coronary artery. Serious morphological changes in the pulmonary vessels such as are observed in the human pulmonary hypertension were not seen in our laboratory animals. Two dogs in each dosage group died in the course of the experiment. The results of this experiment show that it is, in general, possible to induce pulmonary hypertension by administering Aminorex orally. In two dogs, however, pressure in the pulmonary artery (measured under anaesthesia) was below 20 mm Hg (controls: 13.8 +/- 1.3 mm Hg). One possible pathogenetic mechanism underlying the pulmonary hypertension would appear to be precapillary vasoconstriction induced by Aminorex, which can lead to transient, persistent or, for some unknown reason, even permanent fixation of pulmonary resistance.

Drug-induced pulmonary hypertension?

Of 40 patients with obstructive pulmonary hypertension studied in Basle, Switzerland, during the period 1966-68, 32 had been taking an anorectic drug, aminorex fumarate. Rapidly progressing exertional dyspnoea, central chest pain, and syncope on effort were characteristic features. The absence of the usual causes of pulmonary vascular disease seems to suggest the possibility of drug-induced pulmonary hypertension. Further studies are necessary, however, to clarify the role of aminorex fumarate in this condition.