Beta 1 Blockers

[laura/nottingham]

Hi

Anyone help me with this question??

Why could beta 1 blocker cause an asthma attack and why would it be difficult to treat?

I understand that beta blockers reduce the amount of oxygen the heart users. But with asthma, it is the airways that are affected.

I have looked on loads of sites and still not found anything.

Thanks

[Fleegle]

Here's a start...it's a bit old, however it does provide some useful links to other info..

Are Beta-1-Blockers Safe for Patients with Lung Disease? -- 137 (9): I-31 -- Annals of Internal Medicine

Fleegle.

[laura/nottingham]

Thanks for that.

Although, why will it be difficult to treat??

[Sir_Dispensalot]

standard treatment of bronchospasm is with a beta2 agonist. Beta1 blockers also affect beta2 significantly - if the receptor site is blocked then the beta2 agonist won't work, making treatment rather difficult.

[gkswdn]

Hi
There are two types of beta 1 blockers.
1- sectives which act only on heart (Atenolol,metprolol,esmolol,bisoprolol)
2- non-selectives which act on hear even on lungs (sotalol,propranolol,timolol)
with administration of a non-selctive beta 1 blocker to a asthma patient there is risk that beta 2 receptor gets blocked.Asthma patients are dependent on beta2 agonists.There is a reason why those with asthma never get cured.

gkswdn

Hi

Anyone help me with this question??

Why could beta 1 blocker cause an asthma attack and why would it be difficult to treat?

I understand that beta blockers reduce the amount of oxygen the heart users. But with asthma, it is the airways that are affected.

I have looked on loads of sites and still not found anything.

Thanks

[Shwampa]

wow it's getting a bit messier..there's no beta1 receptor in the lungs and prescribing a beta 1 or cardioselective blocker shouldn't cause bronchoconstriction.

The non selective ones that block b1 and b2 are contraindicated in asthma and copd.

view the attached table about the location of the different receptors.

A good article: CV Pharmacology: Beta-Adrenoceptor Antagonists (Beta-Blockers)

[gkswdn]

Hi Shwampa

Thank you for the article.This was my answr to loura.

Bronchoconstriction can occur, especially when non-selective beta-blockers are administered to asthmatic patients. Therefore, non-selective beta-blockers are contraindicated in patients with asthma or chronic obstructive pulmonary disease. Bronchoconstriction occurs because sympathetic nerves innervating the bronchioles normally activate β2-receptors that promote bronchodilation. Blockade of these receptors can lead to bronchoconstriction.

gkswdn

[starhammad]

Dear laura/nottingham - As we are aware that Selective b-blockers are proportionally selective for receptors. i-e atenolol is B1 selective compared to B2 in ratio of 1:20. So, when a patient gets over exposed to the drug, both types of receptors get occupied.
Now remember the treatment of overdosage of B-Blockers (where b-AGONISTS) are useless & Glucagon is needed to reverse), same principle applicable here. Once the receptors in the lungs(b2) are occupied, there is no way to reverse it, other than the drug's half life is reached and its molecules detached from the receptor binding sites. Therefore, until that period of time, management of the patient is quite a difficult task.
However, this is very rare in practice, as B1 selective rarely occupy receptors in the lungs (b2).
Please do let me know if you get your answer!
Thanks.
Regards,
Hammad

[Khans]

B1 Blockers dont cause asthamtic condition only B2 blockers will cause Asthamtic,...

[bolam]

I have also just read up about this, the bronchoconstriction associated with B-blockers is a B2 induced response as by blocking the B2 receptors you prevent the vasodilation of the smooth muscle in the bronchioles. however the CSM recommends that all B antagonists be contraindicated in asthma, and if treatment via a B blocker is required to use a B1 selective.