Tiotropium bromide. A review of its use as maintenance therapy in patients with COPD.
Tiotropium bromide (Spiriva) is a long-acting anticholinergic bronchodilator that maintains bronchodilation for at least 24 hours, allowing once-daily administration. The active moiety is the tiotropium cation (tiotropium); tiotropium bromide 22.5 micrograms is equivalent to 18 micrograms of tiotropium cation. Greater improvements in lung function from baseline (primary endpoint mean trough FEV(1)) were observed with inhaled tiotropium 18 micrograms once daily than with placebo in 6-month and 1-year randomized, double-blind trials in patients with COPD. Tiotropium improved lung function (trough FEV(1) response) more effectively than ipratropium bromide (ipratropium) 40 micrograms four times daily in 1-year clinical trials, and was at least as effective as salmeterol 50 micrograms 12-hourly in 6-month trials. Preliminary data suggest that tiotropium alone or in combination with once-daily formoterol has a greater bronchodilator effect than twice-daily formoterol in patients with COPD. Improvements in patients' perception of health-related quality of life (HR-QOL) or dyspnea were greater with tiotropium than with placebo or ipratropium, and were similar to those with salmeterol. Reductions in the frequency and severity of acute exacerbations and in the use of rescue medication were also greater with tiotropium than with ipratropium or placebo. There was no evidence of tachyphylaxis with tiotropium during 1-year clinical trials. Inhaled tiotropium was generally well tolerated in clinical trials. Apart from dry mouth, the type and incidence of adverse events with tiotropium were similar to those with ipratropium, salmeterol or placebo in patients with COPD. In conclusion, inhaled tiotropium 18 micrograms once daily improved lung function, dyspnea, and HR-QOL, and decreased the incidence of acute COPD exacerbations and the use of rescue medication relative to placebo or ipratropium in clinical trials in patients with COPD. Tiotropium was at least as effective as salmeterol in terms of bronchodilator efficacy and improvements in dyspnea or HR-QOL. With the exception of dry mouth, the tolerability profile of tiotropium was similar to that with placebo, ipratropium, or salmeterol. Consequently, inhaled tiotropium is likely to be a valuable option for first-line, long-term maintenance therapy in the management of bronchoconstriction in patients with symptomatic COPD. Tiotropium bromide has a quaternary ammonium structure and acts as an anticholinergic bronchodilator; the active moiety is the tiotropium cation (tiotropium). A 22.5 micrograms dose of tiotropium bromide provides 18 micrograms of tiotropium. Orally inhaled tiotropium bromide antagonizes the muscarinic M(1), M(2), and M(3) receptors located in airway smooth muscle, reversing vagally mediated bronchoconstriction. Receptor binding assays and in vitro tests indicate that tiotropium bromide is kinetically selective for M(1) and M(3) receptors over the M(2) receptor, unlike ipratropium bromide, which is nonselective. Animal and in vitro studies showed that tiotropium bromide was more potent ( approximate, equals 20-fold) than ipratropium bromide in displacing [(3)H]N-methylscopolamine (NMS) from muscarinic receptors, and had a more sustained protective effect (>70% inhibition) against NMS binding. Tiotropium bromide was a more potent inhibitor of bronchial contraction than atropine ( approximate, equals 23-fold), and had a slower onset and markedly longer duration of action than atropine or an equipotent dose of ipratropium bromide. Aerosol particle penetration is improved with tiotropium, without delaying mucus clearance from the lungs. Tiotropium 4.5-36 micrograms once daily for 4 weeks increased mean trough and average FEV(1) and FVC and mean PEFR values from baseline compared with placebo, with no evidence of tachyphylaxis. Improvements in trough FEV(1) from baseline with tiotropium 4.5-36 micrograms were not dose dependent. Based on a lack of dose response, the optimal once-daily tiotropium dosage is 18 micrograms. Steady-state trough FEV(1) values are achieved within 48 hours of commencing tiotrochodilation (for >/=24 hours) and an attenuation of the nocturnal decline in FEV(1) that were unaffected by timing of the daily tiotropium dose were seen in randomized, double-blind, placebo-controlled studies in patients with stable COPD. The drug improved static and dynamic lung hyperinflation (evidenced by reduced trapped air volume and increased tidal volume and end-of-exercise inspiratory capacity), and improved exertional dyspnea (during activities of daily living and exertion) and exercise tolerance compared with placebo in randomized, double-blind studies. In patients with stable COPD, improved sleep-related oxygen desaturation that was unaffected by the timing of the daily dose was seen with tiotropium but not with placebo. Clinically significant treatment-related disorders of conduction or rhythm, or changes in heart rate were not observed with tiotropium in this patient group. Mean maximal plasma concentrations (C(max)) were observed within 5 minutes of inhalation of a single dose of tiotropium 18 micrograms in patients with COPD. Plasma drug levels declined to minimum concentrations (C(min)) within 1 hour of treatment in healthy volunteers. Mean steady-state C(max) concentrations (16 ng/L) were achieved after 2-3 weeks of once-daily inhaled tiotropium 18 micrograms in elderly patients with COPD; tiotropium does not appear to accumulate once steady-state has been achieved.The estimated absolute bioavailability of tiotropium at steady state in healthy volunteers was approximately 20-25%, and approximately 72% of the drug is bound to plasma proteins. Excretion of tiotropium is predominantly renal (through active secretion by the kidneys), although in vitro studies suggest that cytochrome P450 (CYP) oxidation (possibly involving CYP2D6 and CYP3A4 enzymes) may have a minor role. In patients with COPD, renal excretion of the unchanged drug at 24 hours (Ae(24)) was approximately 7%. The mean plasma elimination half-life after single or multiple doses in healthy volunteers and elderly patients with COPD was approximately 5-6 days. The renal clearance and urinary excretion of tiotropium decrease with increasing age; however, these changes are not considered to be clinically significant. Because of altered steady-state C(max), C(min), area under the concentration-time curve, and Ae(24) values, caution is required with tiotropium administration in patients with moderate-to-severe renal impairment. The pharmacokinetics of tiotropium in patients with severe renal or hepatic impairment have not been studied. Tiotropium does not interact with drugs such as cimetidine or ranitidine, which are also eliminated by active renal secretion. Orally inhaled tiotropium bromide has been evaluated as a bronchodilator for the management of patients with COPD in randomized, double-blind 6-month and 1-year trials, and in several shorter studies. In clinical trials, COPD was diagnosed according to the American Thoracic Society guidelines. The bronchodilator effect was expressed as the trough FEV(1) response (the mean change in FEV(1) from baseline measured 1 hour prior to and immediately before a scheduled dose), and was the primary endpoint in all but two clinical trials. The bronchodilator effect with tiotropium 18 micrograms once daily was superior to that with placebo in several well designed trials in patients with COPD. Moreover, greater improvements in mean peak and average FEV(1) responses occurred with tiotropium but not with placebo. Mean trough, peak, and average FVC responses, and weekly mean morning and evening PEFR values were also improved to a greater extent with tiotropium than with placebo. Tiotropium demonstrated a greater bronchodilator effect than ipratropium bromide (hereafter referred to as ipratropium when used at approved dosages) 40 micrograms four times daily in two 1-year trials in patients with COPD. Mean peak and average FEV(1), mean trough FVC responses, and weekly mean morning and evening PEFR values were also increased to a greater extent with tiotropium than with ipratropium. In one of the two 6-month trials that compared the efficacy of tiotropium with that of inhaled salmeterol 50 micrograms twice daily, greater improvements from baseline in mean trough, peak, and average FEV(1) and FVC responses were seen with tiotropium than with salmeterol. Increases in weekly mean evening, but not morning, PEFR values were generally greater with tiotropium than salmeterol. In the second trial, improvement in the primary endpoint (mean trough FEV(1) response from baseline) with tiotropium or salmeterol was similar, although peak and average responses were superior with tiotropium. Preliminary results from a 6-week crossover study in patients with COPD suggested that tiotropium alone or in combination with once-daily formoterol improved mean trough and average FEV(1) and trough FVC values from baseline to a greater extent than twice-daily formoterol. More patients achieved a clinically important improvement (increase of >/=1 unit) in the transitional dyspnea index focal score (a measure of dyspnea-related impairment) with tiotropium than with placebo in the 1-year trials. Tiotropium was superior to ipratropium in 1-year trials, and was at least as effective as salmeterol in 6-month trials, in achieving a clinically important improvement in focal scores. Tiotropium recipients experienced fewer COPD exacerbations than placebo or ipratropium recipients and had fewer and shorter COPD-related hospitalizations compared with placebo recipients. Unlike salmeterol, tiotropium lengthened the time to onset of the first exacerbation and decreased the number of exacerbations compared with placebo in two 6-month trials. Similar proportions of tiotropium, salmeterol, and placebo recipients required COPD-related hospitalizations. (ABSTRACT TRUNCATED)