Almitrine bismesylate and oxygen therapy in hypoxic cor pulmonale

History of Respiratory Stimulants

The interest in substances that stimulate respiration has waxed and waned throughout the years, intensifying following the introduction of a new class of drugs that causes respiratory depression, and diminishing when antidotes or better drug alternatives are found. Examples include the opioids--deaths increasing during overprescribing, diminishing with wider availability of the opioid receptor antagonist naloxone, increasing again during COVID-19; the barbiturates--until largely supplanted by the benzodiazepines; propofol; and other central nervous system depressants. Unfortunately, two new troubling phenomena force a reconsideration of the status-quo: (1) overdoses due to highly potent opioids such as fentanyl, and even more-potent licit and illicit fentanyl analogs, and (2) overdose due to polysubstance use (the combination of an opioid plus one or more non-opioid drug, such as a benzodiazepine, sedating antidepressant, skeletal muscle relaxant, or various other agents). Since these now represent the majority of cases, new solutions are again needed. An interest in respiratory stimulants has been revived. This interest can be informed by a short review of the history of this interesting class of medications. We present a short history of the trajectory of advances toward more selective and safer respiratory stimulants.

Primary pulmonary hypertension and cor pulmonale

Primary pulmonary hypertension and cor pulmonale represent forms of precapillary pulmonary hypertension due to intrinsic lung disease. In the case of primary pulmonary hypertension, this is due to disease of the pulmonary vasculature while cor pulmonale is related to diseases of the pulmonary vasculature, airways, or interstitium. Patients present with signs and symptoms of right ventricular dysfunction and low cardiac output including dyspnea, chest pain and peripheral edema. Therapy is directed at the underlying disease and may include supplemental oxygen for diseases causing chronic hypoxemia and anticoagulation for thrombotic disease. Vasodilator therapy has variable efficacy for pulmonary vascular disorders. Postacyclin by continuous infusion has been a major advance in the therapy of primary pulmonary hypertension and has prolonged survival and delayed the need for lung transplantation. Bosentan, an endothelin receptor blocking agent is the first oral medication approved for the therapy of pulmonary hypertension.

Prolonged treatment with almitrine for refractory hypoxemia in adult respiratory distress syndrome

A 49-year-old man presented with an atypical pneumonia entailing an adult respiratory distress syndrome (ARDS). The refractory hypoxemia caused a myocardial infarction, leading us to try pharmacologic treatments. Almitrine bismesilate (AB) infusion allowed improvement of arterial oxygenation during 115 h without adverse effect. This case is, to our knowledge, the first reported prolonged treatment using AB for hypoxemia due to ARDS.

Low-dose almitrine bismesylate in the treatment of hypoxemia due to chronic obstructive pulmonary disease

STUDY OBJECTIVE

Assessment of acute and chronic effects of low-dose almitrine bismesylate (AB) in stable chronic obstructive pulmonary disease (COPD).

STUDY DESIGN

Oral administration of AB, 25 mg three times a day, for 6 months in all patients. Pulmonary function, blood gases, and peripheral nerve conduction velocity were measured at baseline and after long-term administration of AB. In addition, oral pharmacokinetics and effects on pulmonary circulation at rest were studied in half of the patients. Intravenous pharmacokinetics were measured after a single intravenous dose of 60 mg of AB 3 months before the start of oral AB treatment in the other seven patients.

SETTING

Outpatient clinic of a community hospital in a coal mining district in southwest Germany.

PATIENTS

Fourteen patients with clinically stable COPD and hypoxemia.

RESULTS

Acute effects of AB were as follows: a significant increase in arterial oxygen tension (PaO2) from 61 +/- 7 mm Hg to 74 +/- 8 mm Hg (p < 0.001), a decrease in arterial carbon dioxide tension (PaCO2) from 41 +/- 8 mm Hg to 38 +/- 7 mm Hg (p < 0.01), a rise of pH from 7.45 +/- 0.04 to 7.48 +/- 0.04 (p < 0.01), and a transient increase in mean pulmonary artery pressure from 26 +/- 7 to 29 +/- 6 mm Hg (not significant). After long-term treatment, once tissues were saturated with almitrine, improvement in gas exchange persisted with a PaO2 of 70 +/- 10 mm Hg (p < 0.001) and a PaCO2 of 39 +/- 6 mm Hg (not significant) without elevation of pH (7.45 +/- 0.04) or of pulmonary artery pressure (26 +/- 8 mm Hg). The terminal half-life of AB was 56 +/- 45 days after a single intravenous administration, and 55 +/- 16 days after long-term oral dosing. None of the patients developed clinically manifest peripheral neuropathy. Impaired asymptomatic peripheral motor nerve function was prevalent in 4 (29 percent) of the patients and remained unchanged during long-term AB administration. However, asymptomatic impairment of motor nerve conduction velocity developed in two patients with inadequate high AB plasma levels despite low-dose therapy. Both patients were known to have additional conditions predisposing for neuropathy.

CONCLUSIONS

Low-dose AB therapy, 75 mg daily, resulted in sustained elevation of arterial oxygen tension in hypoxemic patients with COPD. Although pulmonary artery pressure increased transiently after the first dose, it remained unchanged with long-term treatment despite persistent improvement of pulmonary gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

[The predictive parameters in the response to almitrine treatment]

Almitrine bimesylate (AB) improves hypoxemia in an undetermined number of patients with respiratory failure. Our objective was to try to identify the patients likely to benefit from this treatment. We undertook a double blind study of AB (50-100 mg/day) vs placebo in 21 randomly chosen patients diagnosed as having chronic obstructive bronchitis who were receiving oxygen therapy in the home. The study lasted 3 months (T0 to T3). PaO2 rose from 51 +/- 5.3 to 58.5 +/- 10 mmHg (6.8 +/- 0.7 to 7.8 +/- 1.3 Kpa) in the 12 patients taking AB (p < 0.05). The remaining gasometric variables and results of functional respiratory exploration were unchanged. The 7 patients receiving AB who were defined as responding-whose PaO2 rose more than 5 mmHg (0.66 Kpa)-presented T0 values lower than those of the 7 non-responding patients in the same group, with respect to CO2 occlusion pressure, mean inspiratory flow and minute ventilation for both air and CO2. These variables can serve as predictors for gasometric response to AB.