Cardiovascular and respiratory responses to right atrial injections of phenyl diguanide in pentobarbital-anesthetized newborn piglets

The present series of experiments was designed to determine whether the piglet has mature cardiorespiratory responses to the administration of phenyl diguanide (PDG) similar to those reported in adult mammals. A total of 26 acutely instrumented piglets aged 2--23 days were lightly anesthetized with sodium pentobarbital. After control conditions were established, PDG was injected into the right atrium. Each animal was its own control for determination of presence and magnitude of aortic pressure, heart rate, respiratory rate and volume, and blood flow responses to test doses of PDG. A fall in blood pressure was observed in all animals within 2--4 sec after right atrial injection of PDG. Bradycardia occurred and a transient cardiac arrhythmia, consisting of 2nd and 3rd degree heart block, was observed in most animals; the latter has not been previously reported. Apnea followed by rapid shallow breathing was observed in most animals. This respiratory effect was more pronounced in the younger animals. After atropine, PDG elicited a monophasic rise in aortic pressure; the cardiac rhythm and rate changes were abolished. However, the apneic response was retained. Subsequent bilateral vagotomy abolished the hypotensive effect on PDG. Such results suggest the possibility that the piglet,s cardiorespiratory response to the administration of PDG may be evoked by stimulation of type J pulmonary receptors. These have been postulated to be responsible for the triad of responses of hypotension, bradycardia, and apnea seen in other species after PDG administration.

[Treatment of diabetes without biguanides. Observation on the course after changing treatment (author's transl)]

In 56 patients with maturity onset diabetes receiving combined therapy with different oral hypoglycemic drugs, biguanide treatment was stopped while sulphonylurea compounds were continued without major changes. In four patients insulin therapy had to be initiated rapidly. In 14 other patients follow-up observations could not be performed for various reasons. The reamining 38 patients were divided into four groups according to their treatment. On the average, chemical control could not be maintained in any group after discontinuation of biguanide therapy. Blood glucose concentrations and glycosuria increased. Later, in 6 of 38 patients secondary failure of sulphonylurea treatment became apparent.

Biguanide-induced lactic acidosis in Finland

Twenty-four patients with biguanide-induced lactic acidosis were reported to the Adverse Drug Reaction Register of the Finnish National Board of Health from 1974-1977. Of them, 23 had been treated with phenformin and one with metformin. The mean age of the patients was 71 years, and all but one were more than 65 years of age. The mortality rate was 63%. One patient had cirrhosis of the liver and one was already known tohave had impaired renal function. Fourteen of the patients had a normal serum creatinine concentration either before or after the development of lactic acidosis. Thus, in most patients it had not been possible to prevent development of lactic acidosis by observing the contraindications to biguanide therapy. Most patients had some form of co-existing cardiovascular disease. Tetracycline therapy was a probable precipitating factor in three cases. Based on the statistics of biguanide consumption in Finland, the annual incidence of biguanide-induced lactic acidosis in 1976 and 1977 was between 1/2000 and 1/3000 and that of fatal lactic acidosis was 1/4000.

Tooth staining effects of an alexidine mouthwash

The primary purpose of this study was to determine the amount of tooth staining produced by an alexidine mouthrinse. One hundred and eighty subjects rinsed twice daily for 1 month with either 15 ml of alexidine (0.035%) or a placebo solution. Prior to the study, the subjects were classified according to their smoking, coffee and tea drinking habits and these factors were subsequently considered in the analysis of the stain scores. Additionally, the effects on staining of a prior prophylaxis and the use of a fluoridated toothpaste during the study were determined. Upon termination of the study, subjects utilizing the active mouthrinse manifested a greater degree of staining than placebo users. The amount and intensity of the stain due to alexidine were not influenced (increased) by smoking, tea or coffee drinking habits. A prior prophylaxis did not reduce the staining propensity of alexidine users. The method of scoring developed can be used to assess the degree of tooth staining induced by antiplaque agents.

Cariostatic activity of (1,6-bis-[2-ethylhexylbiguanido]-hexane) in conventional rats

The antimicrobial and cariostatic activities of the dihydrochloride and dihydrofluoride salts of alexidine (1,6-bis-[2-ethylhexylbiguanido]hexane) were compared to those of chlorhexidine acetate and sodium fluoride in rats implanted orally with Streptococcus mutans 6715 and fed a cariogenic diet. Experimental caries was significantly reduced by the continuous administration of low concentrations of biguanides via the drinking water, but this was accompanied by increased staining of the molars. Very high biguanide concentrations, applied infrequently, directly to the molars, effectively reduced caries and resulted in less staining. A combination of alexidine dihydrochloride and sodium fluoride offered no advantage over either drug alone. Alexidine salts prevented the progressive increase in implanted S. mutans, whereas chlorhexidine acetate practically eliminated the micro-organism from the oral cavity. Sodium fluoride had no effect on the implanted flora. It was concluded that alexidine salts are comparable in cariostatic activity to chlorhexidine. The tooth staining accompanying the use of bisbiguanides can be reduced by adjusting the concentration of the drug and its frequency of application.

Oral hypoglycemic drugs and cardiovascular pathology

The classification, the mechanisms of action and the main side effects of sulfonylureic derivatives and biguanides are discussed. Emphasis is laid on the present controversy concerning the assumed adverse effect of these drugs on the cardiovascular system. The authors' opinion in this problem and their practical conclusions are based on their experience at the Center of Nutrition and Metabolic Diseases, Bucharest.

[Serum concentration of lactate in diabetic patients treated with biguanides in relationship to renal function (author's transl)]

Lactate, pyruvate, creatinine, urea, blood sugar and the serum concentration of phenformin or buformin were analyzed in the venous blood of a total of 90 diabetics who received biguanides regularly for at least one month. The creatinine clearance as well as the lactate-pyruvate quotient were computed. Age, body weight and size as well as duration of medication were recorded. Twenty-three diabetics who did not receive biguanides were used for control. Almost all patients revealed a mostly minor hyperlactatemia which was also observed in the control group. There was no significant difference between the two groups. There was no relationship between renal function, the serum lactate level and the biguanide concentration.

[Biguanide-induced and - associated lactic acidosis: serum and tissue biguanide levels in hyperlactaemia and lactic acidosis (author's transl)]

An investigation was carried out on 30 diabetic patients in an attempt to clarify the relationship between serum biguanide levels and raised lactate. No consistent relationship was demonstrable between the serum biguanide level, administered dosage and time of administration. There was also no correlation between biguanide and lactate increase. It is not justifiable to quote a specific serum level of biguanides in defining lactic acidosis. A causal association between biguanide medication and lactic acidosis seems to be possible only by determination of serum and tissue levels. Determination of biguanide levels was carried out in the serum and tissue of a patient who had died as a result of lactic acidosis after phenformin administration. While the serum levels were only slightly higher than the therapeutic range, both liver and kidney tissue showed highly toxic levels. Furthermore, the amount of biguanides in the body was calculated in another patient successfully treated for lactic acidosis after buformin therapy. A differentiation should be made between biguanide-induced and biguanide-associated lactic acidosis. In both forms serum levels can be within relatively low ranges. In the former condition, the biguanides alone are responsible for the development of lactic acidosis by blocking the respiratory chain. In the latter condition they aggravate an already existing pathological condition, and can, therefore, represent a lethal factor.

[Lactacidosis in biguanide therapy: diagnosis and therapy. 4 cases compared to 179 cases in the world literature]

In 4 out of 9711 (= 1:2400) patients, lactice acidosis due to biguanides was diagnosed. Serum lactate concentration averaged 18.2 mmol/l and the pH value 6.87. All patients showed signs of renal insufficiency and three had congestive heart disease. In addition to treatment with biguanides, other factors might have contributed to the lactice acidosis in these patients: prolonged fasting, severe dehydration due to persistent vomiting, acute bronchopneumonia, and acute pyelonephritis. On addmission, two patients were in shock and all patients were semi-conscious or comatose. All patients were treated with bicarbonate and glucose/insulin. One patient was hemodialysed. Two of our four patients died. Oour four patients are compared with 179 patients in the literature with respect to mortality and prognosis of lactic acidosis due to biguanides.

[Lactacidosis in guanide treatment--a current disease syndrome]

It is reported on two eldery female diabetics with severe lethal lactacidosis. The clinical picture as well as the laboratory constellation leave no room for doubt about it, though only in one case the estimation of lactate could be performed. A renal insufficiency as involving factor is to be supposed in the two cases. With the help of literature the essential points of view of the clinical picture are discussed and it is referred to its origin also under influence of buformin.

[Disturbances of taste from oral disinfectants (author's transl)]

Oral disinfectants containing chlorhexidine or hexetidine are able to produce disturbances of taste, as demonstrated by Krarup's electrogustometric method and the gustometric method of Harris and Kalmus. Hypo- and dysgeusia are characterized by dissociated disturbances, the most prominent of which concerns the sweet perception. The bitter taste is least affected, whereas the effects on salty and acidic tastes range between that for sweet and bitter. Taste disturbances which include ageusia for 48 h were observed when the tongue was touched with a 20% solution of chlorhexidine. Not only the disinfectants themselves provoked dysgeusia but also other "taste improving" agents (particularly, the volatile oild). In addition to dysgeusia, the authors found disturbances of the mucous membrane sensitivity caused by the test substances.

[Lactic acidosis--a possible complication in buformin-treated diabetics (author's transl)]

Lactic acidosis is defined as a state of metabolic acidosis (arterial pH below 7.36) due to an increase in the blood concentration of lactate above 2 mEq/l. Lactic acidosis may occur under a variety of conditions; the biguanide-induced lactic acidosis is due to the toxic effects of biguanides (buformin, metformin, phenformin). The clinical picture is characterized by the occurrence of disturbances of consciousness, severe acidosis with Kussmaul's respiration, shock, hypothermia and in about 30% of all cases hypoglycemia. Apart from the general principles of intensive medical care, therapy should comprise correction of the acid-base-disturbances and elimination of the offending biguanide. The efficacy of hemodialysis in the treatment of biguanide-induced lactic acidosis is difficult to evaluate. By a more sensible use of biguanides, lactic acidosis secondary to drug administration should become a rare event.

[The risk of lacticate acidosis: a comparison of the 3 biguanides in treatment of diabetics (authors' transl)]

Hyperlactaemia was induced by means of a standard exercise test in 10 diabetics receiving normal treatment with biguanides (either buformin, metformin, or phenformin) in combination with either a sulfonylurea or insulin. The treatment regimen was then continued without biguanides for 3 weeks and the exercise test was repeated at the end of this period. All 3 biguanide preparations induce hyperlactaemia in diabetics. Physical stress leads to an additional increase in lactate, which reaches pathological proportions. Discontinuation of biguanide treatment leads to a significant decrease in resting and stress values. In a comparison of the 3 biguanide products, phenformin induced significantly higher lactate values in response to exercise than buformin. Of the biguanides, phenformin appears to carry the greatest risk of causing hyperlactaemia in susceptible patients, induced by concurrent circumstances, with progression to severe lacticate acidosis. The special pharmacokinetic properties of phenformin and the 8-fold higher incidence of lacticate acidosis than under buformin or metformin therapy support this observation.