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The Pharmacologic Treatment of Uncomplicated Arterial Hypertension in Patients With Airway Dysfunction^*

^* From the Dipartimento di Pneumologia (Drs. Cazzola, Noschese, and D’Amato), Unità Operativa Complessa di Pneumologia ed Allergologia, Ospedale A. Cardarelli, Napoli, Italy; and the Dipartimento di Medicina Sperimentale (Dr. Matera), Facoltà di Medicina e Chirurgia, Seconda Università Napoletana, Napoli, Italy

Correspondence to: Mario Cazzola, MD, FCCP, Via del Parco Margherita 24, 80121 Napoli, Italy; e-mail: mcazzola{at}qubisoft.it

	Abstract

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Because many antihypertensive drugs can affect airway function, the treatment of hypertension in patients with airway dysfunction is complex. For example, the worsening or precipitation of asthma by ß-adrenoceptor antagonists is well-recognized, but ß₁-adrenoceptor blockers that exert mild ß₂-agonist effects, and those that modulate the endogenous production of nitric oxide, affect airway function to a lesser extent. Therapy with selective ₁-blockers is not contraindicated in cases of chronic airway obstruction. Conversely, ₂-agonists must not be given to asthmatic subjects because they can adversely affect the bronchi. Calcium channel blockers do not exert severe side effects on the airways. Angiotensin-converting enzyme inhibitors may cause cough and exacerbate or even induce asthma; however, angiotensin II type I (AT₁) antagonists do not cause cough. 5-Hydroxytryptamine modifiers such as urapidil are a treatment option for patients with chronic airway obstruction. In patients with airway dysfunction, we suggest treatment with thiazide diuretics as the initial drug choice, and calcium channel blockers if the response is poor. In the case of no response, calcium channel blockers alone must be used. However, there is no strict rule because individual patients may respond differently to individual drugs and drug combinations. Consequently, it is important to adopt a flexible approach. For patients who are unresponsive to the aforementioned drugs, AT₁ receptor antagonists, newer ß₁-adrenoceptor-blocking agents with ancillary properties (eg, celiprolol or nebivolol), and/or vasodilators can be considered.

Key Words: airway response • antihypertensive drugs • arterial hypertension • asthma • COPD

	Introduction

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
The primary aim of the pharmacologic treatment of hypertension is to achieve optimal or normal BP in order to reduce the risk of cardiovascular morbidity and mortality. According to the results of the Hypertension Optimal Treatment trial,¹ the acceptable BP level is < 140/90 mm Hg, and the optimal BP should be < 130/<85 mm Hg. However, patients whose BP was < 150/90 mm Hg were apparently not disadvantaged.

Achieving target BP levels depends on a number of factors, among which are the patient’s risk factors. Thus, attempts should be made to eliminate all reversible risk factors (eg, smoking, elevated cholesterol, and diabetes). Associated clinical conditions should be managed, and elevated BP levels should be treated. Drug treatment should be adjunctive to appropriate lifestyle changes (eg, dietary changes, smoking cessation, and regular exercise).²

The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure² recommends a diuretic or a ß-blocker (Table 1 ) for initial treatment when hypertension is uncomplicated and there are no contraindications to these medications. Nonetheless, according to the World Health Organization-International Society of Hypertension report,³ any of the available medications (ie, diuretics, ß-blockers, angiotensin-converting enzyme [ACE] inhibitors, angiotensin II type 1 [AT₁] receptor blockers, and, in some instances, -blockers) are acceptable for initial therapy.

View larger version (24K): [in this window] [in a new window] [Download PPT slide]   Figure 1. The ways in which several classes of antihypertensive drugs induce bronchospasm and/or cough in patients with airway dysfunction are shown. ß-Adrenoceptor-blocking agents may inhibit the modulatory effect of circulating epinephrine on the ß2-adrenoceptors of cholinergic nerves, thus increasing acetylcholine release. If there is a deficit in M2-autoreceptors in asthmatic patients, the increased acetylcholine cannot switch itself off. Alternatively, these agents may increase the release of tachykinins from airway sensory nerves, thereby increasing bronchoconstriction and airway inflammation. 2-Adrenoceptor agonists may be harmful, mainly when their effect on the CNS is greater, because they induce reflex bronchoconstriction. ACE inhibitor-induced cough and bronchospasm are probably linked to the suppression of kininase II activity. Because ACEs degrade bradykinin and substance P, the inhibition of the enzyme may lead to the accumulation of these potent bronchoconstrictors in the lung, with consequent stimulation of vagal afferents that subserve the cough reflex, particularly the nonmyelinated or C fibers, potentially leading to enhanced cough, bronchial reactivity, or bronchospasm.

	ß-Adrenergic Antagonists

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
ß-Adrenoceptors are widely distributed in human airways and alveoli.⁶ ß₂-Receptors are the predominant adrenoceptors on airway smooth muscle, whereas ß₁-receptors account for 10% and 30% of the adrenoceptors on submucosal glands and alveolar walls, respectively. Being competitive inhibitors of ß-adrenoceptors, ß-adrenoceptor-blocking drugs can cause bronchoconstriction. The severity of the bronchoconstrictor response to a given ß-adrenoceptor-blocking agent is not predictable,⁷ and occurs mainly in patients with reversible bronchial obstruction.⁸ These blocking agents can cause severe bronchoconstriction even in subjects with mild asthma. The dose of ß-adrenoceptor-blocking drugs administered may be low, as in the case of timolol, a nonselective ß-adrenoceptor blocker used to treat glaucoma.⁹

Nonselective ß-Adrenoceptor-Blocking Drugs
Nonselective ß (ß₁ + ß₂)-adrenoceptor-blocking agents can precipitate bronchospasm in patients with asthma. Propranolol and other nonselective ß-adrenergic antagonists, such as timolol and nadolol, block ß₂-adrenoceptors in bronchial smooth muscle.¹⁰ This pharmacologic action usually has little effect on pulmonary function in healthy individuals. However, the antagonistic effect is 66-fold greater in symptomatic asthma patients than in nonasthmatic subjects with inhaled propranolol, and sixfold greater with IV propranolol.¹¹ Consequently, in patients with asthma or COPD, this treatment can lead to life-threatening bronchoconstriction.¹²

ß₁-Selective Adrenoceptor-Blocking Drugs
Most of the adverse pulmonary effects exerted by ß-adrenoceptor-blocking drugs in asthma or COPD patients are related to interference with ß₂-adrenoceptor-mediated bronchodilation. Various studies^{13 14 15 16 17 18} have identified relevant differences in the impact on airway function, depending on whether a ß-blocker is ß₁-selective or ß₁-nonselective. For example, Ellis et al¹⁴ compared the effect of three doses (50, 100, and 200 mg) of atenolol, a selective ß₁-adrenoceptor-blocking drug, and one dose (40 mg) of propranolol on the airways of 10 asthmatic patients. Two hours after drug administration, the three doses of atenolol were significantly less effective than propranolol in ß₂-blocking, as shown by a smaller FEV₁ decrease. Moreover, the isoprenaline FEV₁ dose-response curves gradually shifted to the right of the placebo curve with increasing doses of atenolol, and the greatest displacement was observed with propranolol.

Also ß₁-selective receptor blockers can adversely affect airways at therapeutic oral doses. For example, a 3-week course of atenolol, 100 mg once daily, or metoprolol, 100 mg twice daily, was effective in reducing BP in 14 hypertensive patients with asthma.¹⁸ However, atenolol caused significantly less bronchospasm than metoprolol, less frequent sensations of moderately severe to very severe wheeziness, and more asthma-free days, and had less effect on the evening peak expiratory flow rate (PEFR). This finding suggests that the true clinical relevance of ß₁-adrenoceptor selectivity be re-examined.

All selective ß₁-adrenoceptor antagonists block ß₂-adrenoceptors when their concentrations are high enough, therefore the parenteral route of administration is best avoided.¹⁹ The so-called ß₁-adrenoceptor blockers are not completely ß₁-selective, which could mean that they might have some affinity for ß₂-adrenoceptors on airway smooth muscle. Moreover, the airways may contain functional ß₁-adrenoceptors.²⁰ Nevertheless, esmolol, a new ultra-short-acting ß₁-selective adrenoceptor blocker, may be preferred over propranolol because of its short duration of action and relative lack of effect on airway resistance in patients with asthma who require treatment with an IV ß-adrenoceptor-blocking agent.²¹

Nonselective ß-Adrenoceptor-Blocking Agents With Intrinsic Sympathomimetic Activity
The therapeutic importance of intrinsic sympathomimetic activity (ISA), an ancillary pharmacologic property of some ß-adrenoceptor-blocking drugs, in asthmatic patients is questionable. Apparently, ISA seems to be at least as important as ß₁-adrenoceptor selectivity in reducing the increase in airway resistance that results from ß-adrenoceptor blockade both at rest and during exertion.²² Moreover, it reduces the bronchoconstrictor response to inhaled histamine during ß-adrenoceptor blockade in asthma patients.²³

Patakas et al²⁴ demonstrated that propranolol, but not the nonselective ß-adrenoceptor-blocking agent pindolol that exerts ISA, significantly affected specific airway conductance and PEFR, although tests of small airway function after pindolol administration showed reduced airflow. Unfortunately, the bronchodilator action of terbutaline on large airways was diminished after the administration of both ß-blockers.

Decalmer et al²⁵ examined the effects of approximately equipotent single oral doses of selective ß₁-adrenoceptor-blocking agents (atenolol, 100 mg; metoprolol, 100 and 300 mg) and four nonselective ß (ß₁ + ß₂)-blockers (propranolol, 100 mg; oxprenolol, 100 mg; timolol, 10 mg; and pindolol, 5 mg). Lindolol is the only agent with ISA on FEV₁ in 10 asthma patients. All drugs caused a fall in FEV₁, but only atenolol did not differ significantly from placebo in this respect. Moreover, the four nonselective ß-adrenoceptor-blocking drugs blocked the bronchodilator response to inhaled isoprenaline, whereas the selective ß₁-adrenoceptor-blocking agents allowed some bronchodilation.

These observations indicate that pindolol is potentially dangerous in asthmatic patients. In any case, agents with ISA offer less cardioprotection than do ß-adrenoceptor blockers without this ancillary property. Therefore, the use of these drugs should be severely restricted.

ß₁-Adrenoceptor Blockers With Mild ß₂-Agonist Properties
The new ß-adrenoceptor blockers that have enhanced ß₁-selectivity and partial ß₂-agonist activity affect airway function to a lesser extent than did the earlier blocking agents, but none are considered to be entirely "safe" in patients with asthma. Celiprolol, a ß₁-selective adrenergic-blocking drug with peripheral ß₂-stimulatory, peripheral ₂-inhibitory, and partial agonist activities, has been reported to relax bronchial smooth muscle.²⁶ Isolated tissue studies suggest that a weak ₂-blocking effect contributes to this bronchodilation.²⁶ These findings are encouraging, but clinical experience with these new agents in the treatment of patients with chronic airway obstruction is limited.

In 34 asthmatic patients, propranolol, 40 mg, and to a lesser extent atenolol, 100 mg, but not celiprolol, 200 or 400 mg, caused decreases in FEV₁ and the midexpiratory phase of forced expiratory flow.²⁷ Positive changes in FEV₁ after the administration of each drug plus isoproterenol or albuterol were as follows, in the rank order: celiprolol approximately the same as placebo, greater than atenolol, greater than propranolol. Only propranolol pretreatment caused a significant reduction in the bronchodilator effect.

In normotensive asthmatic patients, the effect of celiprolol, 200 mg or 400 mg, on airways was not significantly different from that of placebo.²⁸ Conversely, propranolol, 80 mg, caused a significant decrease in FEV₁ and FVC, and a conspicuous rise in airway resistance compared with placebo. Terbutaline caused further bronchodilation after the administration of celiprolol and placebo, but it did not restore pulmonary function parameters to baseline levels after propranolol administration, even at supratherapeutic doses.

ß₁-Adrenoceptor Blockers That Modulate the Endogenous Production of Nitric Oxide
Nebivolol, a new selective ß₁-adrenoceptor-blocking agent without ISA, modulates the endogenous production of nitric oxide. In particular, nebivolol dilates the human forearm vasculature via the L-arginine/nitric oxide pathway.²⁹ Nebivolol does not significantly decrease airway conductance compared with atenolol or propranolol.²⁹ In six healthy volunteers, nebivolol, unlike propranolol and atenolol, did not antagonize the effects of albuterol.³⁰ In 12 asthmatic patients, nebivolol had a slight effect on airway function.³¹ However, although its effect on FEV₁ was statistically significant, the mean percent decrease was small (-8.4%). Nebivolol partially antagonized the bronchodilator response to inhaled albuterol, but the effect was similar to that elicited by celiprolol.

Because of the potential role of nitric oxide in airway control,³² ß₁-adrenoceptor blockers that modulate the endogenous production of nitric oxide might be a treatment option, but further research is needed to better assess the impact of these drugs on patients with chronic airflow limitation.

Possible Mechanisms of ß-Adrenoceptor Blocker-Induced Asthma
The mechanisms of ß-adrenoceptor blocker-induced asthma are uncertain. The bronchoconstrictor effects of these drugs seem to be unrelated to ß-adrenoceptor blockade in the airway smooth muscle.³³ Marcelle³⁴ observed that, in healthy subjects and asymptomatic patients, inhaled norepinephrine induced bronchoconstriction and respiratory asynchronism only after pretreatment with low doses of propranolol. Moreover, the airway resistance increases were prevented by phentolamine. These findings indicate that resting bronchial tone is relaxed by the stimulation of ß-adrenergic receptor stimulation, while receptor suppression unmasks -adrenergic-induced constriction.

It also has been suggested that ß-adrenoceptor blockers may inhibit the action of catecholamines on some target cells (eg, airway mast cells) and consequently induce an increase in mediator release.³⁵ However, no increase in plasma histamine level was detected after IV propranolol administration.³⁶

There is some indication that muscarinic M₂-receptors, which act as autoreceptors on postganglionic cholinergic nerves and inhibit acetylcholine release, may be defective in asthmatic patients (possibly as a consequence of airway inflammation) and that this may enhance cholinergic reflexes and account for ß-adrenoceptor blocker-induced asthma.³⁷ In fact, ß-blockers may inhibit the modulatory effect of circulating epinephrine on ß₂-adrenoceptors of cholinergic nerves, thus increasing acetylcholine release. If there is a deficit in M₂-autoreceptors, the increase in acetylcholine cannot switch itself off. The inhibitory effect of oxitropium bromide, an inhaled anticholinergic drug, on ß-adrenoceptor blocker-induced asthma supports this theory.³⁷ Alternatively, ß-blockers may increase the release of tachykinins from airway sensory nerves, thereby increasing bronchoconstriction and airway inflammation.³⁸ Boskabady and Snashall¹¹ have suggested that antagonism by ß-blocking drugs is enhanced in asthmatic patients because these patients are more sensitive to endogenous epinephrine, which may thus dilate and stabilize their airways.

Use of ß-Adrenoceptor Blocker in Patients With Airway Dysfunction
Since selective ß₁-adrenoceptor blockers can reduce lung function, ß-adrenoceptor-blocking agents must not be given to patients with airway dysfunction (ie, asthma or COPD), especially those with marked reversibility of airflow. At present, a history of asthma remains a contraindication to the use of any ß-adrenergic inhibitor. However, if these agents are thought to confer a substantial benefit in, for example, a patient affected by a bronchospastic disorder after an acute myocardial infarction, then the lowest dose of a selective ß₁-adrenoceptor-blocking drug without ISA (eg, metoprolol, atenolol, or esmolol) that is associated with high doses of a ß₂-agonist may outweigh the risks in some patients with mild intermittent asthma or well-controlled mild persistent asthma (Table 2 ).³⁹ Obviously, ß₁-blockers should be administered under direct medical observation.⁴⁰

It must be stressed that the American Academy of Allergy and Immunology warned of a potential increased risk associated with the concomitant administration of allergen immunotherapy and ß-blocking agents.⁴¹ The position statement recommended that, when possible, an equally safe and effective drug should substitute for ß-blockers.⁴¹

	Selective 1-Adrenoceptor Antagonists

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Experimental results⁴² and clinical results⁴³ indicate that asthma does not involve significant increases in airway ₁-adrenoceptor function. However, such ₁-adrenoceptor antagonists as indoramin⁴⁴ and phentolamine,⁴⁵ sometimes produce an appreciable improvement in lung function. The weak bronchodilation ascribed to ₁-antagonists could be explained by other pharmacologic actions of the drugs used. In fact, hybrid drugs, such as indoramin and phentolamine, are -adrenoceptor antagonists that exert antihistamine and antiserotonin activities.⁴⁶

Unfortunately, bronchodilation, albeit weak, after the administration of ₁-adrenoceptor antagonists has not been confirmed in a few studies. For example, there were no significant differences in pulmonary function tests in a 6-h study⁴⁷ in patients with essential hypertension and COPD after dosing with placebo or with prazosin. Moreover, the addition of oral prazosin (2 mg twice daily) to previous antiasthmatic medication for 3 weeks in stable patients with chronic asthma who continued to have symptoms despite conventional treatment did not induce significant changes in PEFR, FEV₁, FVC, FEV₁/FVC ratio, diary card symptom scores, or dose of a ß-sympathomimetic agent.⁴⁸

Apparently, selective ₁-blockers do not exacerbate preexisting airflow limitations.⁴⁹ Therefore, chronic obstruction of airways is not a contraindication to selective ₁-blocker prescription.

	2-Adrenoceptor Agonists

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Human bronchial, cholinergic neurotransmission can be inhibited by the stimulation of prejunctional ₂-adrenoceptors.⁵⁰ However, the effects of ₂-adrenoceptor agonists on the human bronchi may either be harmful or beneficial. In fact, when inhaled, they reduce the immediate bronchial response to allergens, whereas when ingested, they increase the bronchial response to histamine, mainly when their effect on the CNS is greater.⁵¹ Actually, clonidine does not modify the response to histamine in nonasthmatic patients but significantly increases it in asthmatic subjects.⁵² On the contrary, it does not significantly affect methacholine-induced bronchoconstriction in asthma patients.⁵³

Reports on the effects of ₂-adrenoceptor agonists in patients with airway dysfunction are scarce. Deitch et al⁵⁴ evaluated the effects of guanabenz on the airways of COPD patients. Only 1 of 64 patients discontinued guanabenz treatment because of asthma exacerbation that was thought to be due to airway dryness. Because of these conflicting findings and the lack of more detailed information, we believe that ₂-adrenoceptor agonists should not be used in asthmatic subjects due to their potential harmful effects on the bronchi.

	Combined -Adrenergic and ß-Adrenergic Receptor Blockers

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Labetalol is an antihypertensive agent that combines a nonspecific ß₁-blocker and ß₂-blocker with some ₁-blocking activity. These pharmacodynamic actions can affect lung function. In fact one report⁵⁵ suggests that the coexistent ₁-adrenoceptor blockade does not prevent asthmatic symptoms caused by the ß-adrenoceptor blockade. For example, in six healthy male volunteers, the changes in FEV₁ induced by a 400-mg dose of labetalol did not differ from those of placebo, whereas an 80-mg dose of propranolol reduced resting FEV₁ and enhanced the fall in FEV₁ after histamine administration.⁵⁶ Moreover, Dal Negro et al⁵⁷ showed that three ß-adrenoceptor-blocking agents (ie, atenolol, oxprenolol, and metoprolol) caused significant worsening of pulmonary functional parameters in hypertensive patients who also had COPD. On the contrary, labetalol led to a mild improvement in respiratory function.

Carvedilol, a nonselective ß-adrenoceptor antagonist that is devoid of ISA and that possesses vasodilator properties secondary to selective ₁-adrenoceptor-blocking activity that is considerably weaker than its ß-adrenoceptor antagonistic activity,⁵⁸ does not elicit any noteworthy effect on pulmonary function.⁵⁹ In particular, Guazzi et al⁶⁰ have demonstrated that in chronic heart failure, carvedilol ameliorates left ventricular function at rest and does not significantly affect ventilation and pulmonary gas transfer or functional capacity.

Notwithstanding these reports, we believe that the combination of -adrenoceptor and ß-adrenoceptor blockers is potentially dangerous because the -adrenoceptor blockade might fail to prevent the asthmatic symptoms caused by the blockade of ß-adrenoceptors.

	Diuretics

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Loop diuretics, including the clinically efficacious agents bumetanide and furosemide,⁶¹ and thiazides⁶² inhibit Na-K-Cl cotransport activity. The Na-K-Cl cotransporters are a class of membrane proteins that transport Na, K, and Cl ions into and out of cells in an electrically neutral manner. Cotransporter regulation is highly tissue-specific, which perhaps in part is related to the presence of different Na-K-Cl cotransporter isoforms.⁶³ The Na-K-Cl cotransporter mediates both K⁺ influx and efflux in airway smooth muscle. Na-K pump inhibition stimulates outward Na-K-Cl cotransport as a result of an increase in intracellular Na⁺ content.

These findings explain why thiazide diuretics do not have significant adverse effects on airway function and may be considered the agents of choice for initial therapy in patients with asthma. On the contrary, loop diuretics are generally not considered for use as antihypertensive medication because their effect on reducing peripheral vascular resistance is smaller when compared to thiazide diuretics.

However, diuretics may interfere with mucus production.⁶⁴ Moreover, thiazide diuretics must be used with caution in hypertensive patients with COPD. In fact, being potassium-wasting diuretics, they may worsen CO₂ retention in hypoventilating patients and potentiate hypokalemia in those patients receiving corticosteroids. In addition, ß-agonists may substantially lower serum potassium levels in patients already rendered hypokalemic by diuretics.

Patients with COPD receiving potassium-wasting diuretics who have chronic respiratory acidosis or are receiving corticosteroids or ß-agonists should undergo close monitoring of electrolyte levels and be considered for therapy with potassium supplements or, preferably, potassium-sparing agents.⁶⁵ However, although thiazides are potentially dangerous in patients with COPD, significantly fewer adverse effects have been reported with these diuretics since the finding that low doses can be clinically beneficial.

	Calcium Channel Blockers

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Calcium plays a central role in the activation of many cellular processes, including contraction, which is the most relevant end point in airway smooth muscle physiology.⁶⁶ Although the maintenance of tone may depend on some calcium entry, this may be also via channels that are not sensitive to conventional calcium antagonists.³⁵ Similarly, the release of mediators from inflammatory cells is not mediated via voltage-dependent calcium channels, and there is no evidence that calcium antagonists have a significant effect on mediator release, the activation of inflammatory cells, or the process of inflammation.³⁵

Nevertheless, some calcium channel blockers may have beneficial or neutral effects in hypertensive patients with asthma or COPD because they can alter nonspecific airway hyperreactivity. For example, Kivity et al⁶⁷ observed that nifedipine (20 mg), but not diltiazem (60 mg), significantly raised the provocative concentration of methacholine causing a 20% fall in FEV₁ (PC₂₀) in asthmatic patients when compared with placebo. When diltiazem was given alone, it had no effect on the airway but, when given with nifedipine, it significantly raised the PC₂₀. This effect was superior to that of any of the other treatments that were given. It has been suggested⁶⁸ that nifedipine exerts an effect principally on mediators that are dependent on external calcium sources, such as methacholine, for stimulus-contraction coupling in the airways. However, nifedipine also inhibited the exercise fall in FEV₁.⁶⁹ It is noteworthy that nifedipine induces a small potentiation of ß₂-adrenoceptor-mediated bronchodilation, which is important when treating patients affected by both asthma and hypertension.⁷⁰

Calcium channel blockers may be given to hypertensive patients who are affected by airway disease instead of other harmful antihypertensive agents because they do not adversely affect the airways. They may be a good alternative to ß-adrenergic antagonists in that they may also possess some bronchodilating effects.

	ACE Inhibitors

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Whereas ACE inhibition is safe in the vast majority of patients with obstructive airway disease, asthmatic symptoms, the exacerbation of asthma, and a rise in bronchial reactivity occasionally have been reported.⁷¹ A dry cough, which may not necessarily occur shortly after the institution of therapy but perhaps months or even a year later, is the most common adverse effect of ACE inhibitors.⁷² Cough has emerged as a drug class effect of all ACE inhibitors.⁷³ Controlled studies⁷⁴ have suggested that the incidence may be as high as 20%, and the problem seems to occur much more often in women. No links with sex, history of bronchospasm, drug type, or drug dose have been identified, although ACE expression is decreased in the epithelium of asthmatic patients and is associated with increased eosinophil inflammation.⁷⁵

ACE inhibitor-induced cough and bronchospasm are probably linked to the suppression of kininase II activity. ACE catalyzes the conversion of angiotensin I into angiotensin II. It also inhibits the action of kininase II, which may lead to an accumulation of bradykinin (Fig 2 ) and substance P in the lung. Bradykinin may induce cough and bronchospasm in susceptible persons by stimulating sensory C-fibers and phospholipase A₂, which increases the production of arachidonic acid metabolites and prostaglandins (PGs), especially PGE₂ and PGI₂. Substance P, being a neurotransmitter for C-fibers, produces bronchoconstriction.

View larger version (12K): [in this window] [in a new window] [Download PPT slide]   Figure 2. Endocrine ACE systems.

Since ACE inhibitors may cause dry cough during treatment, and occasionally may worsen or even induce asthma, they could be hazardous in asthmatic patients. In any case, in patients who develop cough after the assumption of an ACE inhibitor, theophylline⁷⁶ or cromolyn sodium⁷⁷ therapy can reduce the extent of the symptom.

	AT1 Receptor Antagonists

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
AT₁-antagonists (eg, losartan, valsartan, irbesartan, or candesartan) are recommended as an alternative for patients at risk for cough while receiving ACE inhibitors.⁷⁸ In fact, these drugs, unlike ACE inhibitors, are selective and do not block the effects of kininase II, so they neither lead to the accumulation of bradykinin or substance P (Fig 2) nor enhance PG synthesis.⁷⁹ A study⁸⁰ of AT₁-blockers suggested that cough has a similar prevalence in patients taking the drug (prevalence, 2.8 to 3.4%) and patients taking placebo. However, in a randomized study,⁸⁰ losartan induced cough in 29% of subjects.

There are several reports^{81 82 83} of cases of losartan-induced bronchoconstriction that may result from the inhibition of endogenous nitric oxide release in the airway.⁸⁴ This finding was unexpected because it is well-known that IV angiotensin II causes bronchoconstriction in patients with mild asthma⁸⁵ and potentiates methacholine-induced bronchoconstriction both in vitro and in vivo,⁸⁶ although it has no effect on histamine-evoked bronchoconstriction in human bronchi in vitro or in vivo⁸⁷ and it does not potentiate endothelin-1-induced bronchoconstriction at sub-bronchoconstrictor doses in asthma patients.⁸⁸ Furthermore, the renin-angiotensin system is activated in a subpopulation of asthmatic patients during acute attacks of severe asthma, although the mechanism of this activation remains unclear.⁸⁹ Since angiotensin II levels are elevated in these patients, a beneficial effect of AT₁-antagonists is possible. Recently, Myou et al⁹⁰ demonstrated that bronchial hyperresponsiveness to methacholine, in terms of a provocative concentration of methacholine causing a 35% fall in standardized partial expiratory flow at 40% of FVC but not PC₂₀ FEV₁, was attenuated by losartan in eight asthmatic patients.

AT₁-antagonists seem to be reasonable alternatives for patients with ACE-inhibitor cough. However, clinical experience is very limited, and, consequently, there is no detailed information regarding adverse reactions to AT₁-antagonists. Moreover, according to some reports, AT₁-receptor antagonists may not be entirely free of ACE inhibitor-related side effects.

	5-HYDROXYTRYPTAMINE MODIFIERS

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
5-Hydroxytryptamine (5-HT) induces a bimodal response in human tracheal and bronchial tissue, which reflects the effect of two 5-HT receptor subtypes.⁹¹ The direct contractile effects of 5-HT are probably mediated through 5-HT2A sites on smooth muscle, whereas the relaxant effects are probably due to the activation of 5-HT1A receptors (Fig 3 ).^{92 93}

View larger version (32K): [in this window] [in a new window] [Download PPT slide]   Figure 3. The possible effects of 5-HT on human airway smooth muscle. 5-HT activates 5-HT2A and 5-HT1A receptors on airway smooth muscle to cause muscle constriction and relaxation, respectively. In addition, some of the released 5-HT acts on presynaptic 5-HT3 and 5-HT7 receptors at the parasympathetic nerve terminal to facilitate the release of acetylcholine (ACh).

One study⁹⁵ has shown that ketanserin produces mild bronchodilation in patients with chronic obstruction of the airways when administered IV in a 10-mg dose. IV ketanserin has a rapid onset of action and induces a more prolonged bronchial response than does inhaled ketanserin.⁹⁵ Ketanserin, which has been tested in asthma patients, had only a marginal effect on methacholine-induced bronchospasm.⁹⁶ However, it attenuated adenosine-induced bronchoconstriction but did not inhibit histamine-induced bronchoconstriction in adult asthmatic subjects.⁹⁷ Moreover, ketanserin did not attenuate exercise-induced bronchoconstriction in adult asthma patients⁹⁸ or in children with atopic asthma.⁹⁹

Urapidil is a peripheral postsynaptic ₁-adrenoceptor antagonist that exerts central agonistic action at 5-HT1A receptors. This antihypertensive agent exerts beneficial effects on pulmonary and cardiac hemodynamics when administered IV or orally to COPD patients with secondary pulmonary hypertension or cor pulmonale.¹⁰⁰ Furthermore, the IV administration of urapidil caused a moderate bronchodilation in patients with obstructive airway disease.¹⁰¹

	Conclusion

TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 
Not all antihypertensive drugs should be used to treat uncomplicated systemic arterial hypertension in patients with concurrent airway dysfunction (Table 3 ). Based on the reviewed literature, we suggest that thiazide diuretics or calcium channel blockers be prescribed for these patients (Fig 4 ) because the majority of cases of hypertension can usually be controlled by one drug, even if it is not the first agent chosen for treatment. For many patients, however, a single drug fails to produce the recommended or optimal BP levels.¹ In that case, managing hypertensive patients who have asthma or COPD requires constant supervision of medication usage and a careful review of the entire list of medications at each presentation. In any case, every effort should be made to reduce the possibility of deleterious effects on airways.

View larger version (30K): [in this window] [in a new window] [Download PPT slide]   Figure 4. A proposed algorithm for the treatment of uncomplicated hypertension in patients with airway dysfunction. The goal BP is < 150/90 mm Hg, according to the Hypertension Optimal Therapy study.1

	Acknowledgements

 
We are grateful to Dr. Jean Ann Gilder for revising the text.

	Footnotes

 
Abbreviations: AT₁ = angiotensin II type 1; ACE = angiotensin-converting enzyme; 5-HT = 5-hydroxytryptamine; ISA = intrinsic sympathomimetic activity; PC₂₀ = provocative concentration of methacholine causing a 20% fall in FEV₁; PEFR = peak expiratory flow rate; PG = prostaglandin

Dr. Cazzola has been reimbursed by the following companies for speaking at educational symposiums, consultancy work, research funding, or attending scientific meetings: GlaxoSmithKline, AstraZeneca, Novartis Pharma, Eli Lilly, Bayer, Menarini Farmaceutici, Chiesi Farmaceutici, Abbott, Lusofarmaco, Malesci. Dr. D’Amato has been reimbursed by the following companies for speaking at educational symposiums, consultancy work, research funding, or attending scientific meetings: GlaxoSmithKline, AstraZeneca, Novartis Pharma, Menarini Farmaceutici, Boehringer Ingelheim, Shering Plough, Gentili, Aventis.

Received for publication June 1, 2000. Accepted for publication May 17, 2001.

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TOP Abstract Introduction ß-Adrenergic... Selective {alpha}1-Adrenoceptor... {alpha}2-Adrenoceptor Agonists Combined {alpha}-Adrenergic and... Diuretics Calcium Channel Blockers ACE Inhibitors AT1 Receptor Antagonists 5-hydroxytryptamine modifiers Conclusion References

 

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