Nebivolol is a β1 receptor blocker with nitric oxide-potentiating vasodilatory effect used in treatment of hypertension and, in Europe, also for left ventricular failure. It is highly cardioselective under certain circumstances.
§Pharmacology and biochemistry
§β1 Selectivity
Beta blockers help patients with cardiovascular disease by blocking β receptors, while many of the side-effects of these medications are caused by their blockade of β2 receptors. For this reason, beta blockers that selectively block β1 adrenergic receptors (termed cardioselective or β1-selective beta blockers) produce fewer adverse effects (for instance, bronchoconstriction) than those drugs that non-selectively block both β1 and β2 receptors. Nebivolol has been marketed by Cipla Ltd under brand name Nebicip; by Forest Laboratories under the name Bystolic; by Micro Labs under the brand name Nebilong; ; and by Menarini under the names Hypoloc, Lobivon, Nebilet, Nebilox, Nebiten, and Temerit.
In a laboratory experiment conducted on biopsied heart tissue, nebivolol proved to be the most β1-selective of the β-blockers tested, being approximately 3.5 times more β1-selective than bisoprolol. However, the drug's receptor selectivity in humans is more complex and depends on the drug dose and the genetic profile of the patient taking the medication. The drug is highly cardioselective at 5 mg. In addition, at doses above 10 mg, nebivolol loses its cardioselectivity and blocks both β1 and β2 receptors. (While the recommended starting dose of nebivolol is 5 mg, sufficient control of blood pressure may require doses up to 40 mg). Furthermore, nebivolol is also not cardioselective when taken by patients with a genetic makeup that makes them "poor metabolizers" of nebivolol (and other drugs) or with CYP2D6 inhibitors. As many as 1 in 10 whites and even more blacks are poor CYP2D6 metabolizers and therefore might benefit less from nebivolol's cardioselectivity although currently there are no directly comparable studies.
§Vasodilator action
Nebivolol is unique as a beta-blocker. Unlike carvedilol, it has a nitric oxide (NO)-potentiating, vasodilatory effect. Along with labetalol, celiprolol and carvedilol, it is one of four beta blockers to cause dilation of blood vessels in addition to effects on the heart. However, recent studies question the clinical relevance of this property to Nebivolol's efficacy.
§Antihypertensive effect
Nebivolol lowers blood pressure (BP) by reducing peripheral vascular resistance, and significantly increases stroke volume with preservation of cardiac output. The net hemodynamic effect of nebivolol is the result of a balance between the depressant effects of beta-blockade and an action that maintains cardiac output. Antihypertensive responses were significantly higher with nebivolol than with placebo in trials enrolling patient groups considered representative of the U.S. hypertensive population, in Black patients, and in those receiving concurrent treatment with other antihypertensive drugs.
§Pharmacology of side-effects
Several studies have suggested that nebivolol has reduced typical beta-blocker-related side effects, such as fatigue, clinical depression, bradycardia, or impotence. However, according to the FDA
§FDA warning letter about advertising claims
In late August 2008, the FDA issued a Warning Letter to Forest Laboratories citing exaggerated and misleading claims in their launch journal ad, in particular over claims of superiority and novelty of action.
§Contraindications
- Hepatic insufficiency
- Children
- Pregnancy
- Lactation
§Adverse drug reactions
- Headache
- Parasthesia
- Dizziness
§History
Mylan Laboratories licensed the U.S. and Canadian rights to nebivolol from Janssen Pharmaceutica N.V. in 2001. Nebivolol is already registered and successfully marketed in more than 50 countries, including the United States where it is marketed under the brand name Bystolic from Mylan Laboratories and Forest Laboratories. Nebivolol is manufactured by Forest Laboratories.
In India, nebivolol is available as Nebistol (Eris life-sciences), Nebicip (Cipla ltd), Nebilong (Micro Labs), Nebistar (Lupin ltd), Nebicard (Torrent), Nubeta (Abbott Healthcare Pvt Ltd â€" India), and Nodon (Cadila Pharmaceuticals). In Greece and Italy, nebivolol is marketed by Menarini as Lobivon. In the Middle East, Russia and in Australia, it is marketed under the name Nebilet and in Pakistan it is marketed by The Searle Company Limited as Byscard.
§Synthesis
Exhaustive hydrogenation of the chromone (1) leads to a reduction of both the olefin and the ketone group (cf. ablukast also). The carboxylic acid then undergoes partial reduction to an aldehyde (2) by means of DIBAL. Reaction of that intermediate with the ylide from trimethylsulfonium iodide gives the oxirane (3) via an addition-displacement process. Treatment of an excess of that epoxide with benzylamine leads to the addition of two equivalents of that compound with each basic nitrogen (4). The product is then debenzylated by catalytic reduction over palladium to afford nebivolol (5). The presence of four chiral centers in the product predicts existence of 16 chiral pairs.
§References
§External links
- Prescribing Information for BYSTOLIC