Editing Beta blocker (section)

=== Contraindications and cautions ===
{{One source|section|date=November 2022}}
{{div col|colwidth=30em}}Absolute contraindications:
* [[Bradycardia]]<ref name="Wyeth Propranolol" />
* [[Hypotension]]
* [[Hypersensitivity]] to beta blockers<ref name="Wyeth Propranolol" />
* [[Cardiogenic shock]]<ref name="Wyeth Propranolol" />
* Second or third degree AV block

Relative contraindications, or contraindications specific to certain beta-blockers:
* Long QT syndrome: sotalol is contraindicated
* History of [[torsades de pointes]]: sotalol is contraindicated

Cautions:
* Abrupt discontinuations
* Acute [[bronchospasm]]<ref name="Wyeth Propranolol">{{Cite web| author = Wyeth |title=Propranolol hydrochloride |url= https://www.accessdata.fda.gov/drugsatfda_docs/label/2007/016418s078lbl.pdf |access-date=2020-09-03 }}</ref>
* Acute [[heart failure]]<ref name="Wyeth Propranolol" />
* [[Asthma]]: see below
* [[Bronchitis]]<ref name="Wyeth Propranolol" />
* [[Cerebrovascular disease]]
* [[Chronic obstructive pulmonary disease|Chronic obstructive pulmonary disease (COPD)]]
* [[Emphysema]]<ref name="Wyeth Propranolol" />
* [[Kidney failure]]
* [[Liver disease|Hepatic disease]]
* [[Myopathy]]
* [[Pheochromocytoma]]
* [[Psoriasis]]
* Raynaud phenomenon
* [[Stroke]]
* [[Vasospastic angina]]
* [[Wolff–Parkinson–White syndrome]]<ref name="Wyeth Propranolol" />{{div col end}}

==== Asthma ====
The 2007 National Heart, Lung, and Blood Institute ([[NHLBI]]) asthma guidelines recommend against the use of non-selective beta blockers in asthmatics, while allowing for the use of cardio selective beta blockers.<ref name="NHLBI Asthma 07">{{cite journal | vauthors = ((National Heart, Lung, and Blood Institute)) | author-link = National Heart, Lung, and Blood Institute | title = Expert Panel Report 3 (EPR-3): Guidelines for the Diagnosis and Management of Asthma–Summary Report 2007 | journal = [[The Journal of Allergy and Clinical Immunology]] | volume = 120 | issue = 5 | pages = S94–S138 | year = 2007 | url = https://www.jacionline.org/article/S0091-6749(07)01823-4/fulltext | doi = 10.1016/j.jaci.2007.09.029 | access-date = 2017-12-09 | archive-url = https://web.archive.org/web/20210828002833/https://www.jacionline.org/article/S0091-6749%2807%2901823-4/fulltext | doi-access = free | archive-date = August 28, 2021 }}</ref>{{rp|182}}

Cardio selective beta blocker (β<sub>1</sub> blockers) can be prescribed at the least possible dose to those with mild to moderate respiratory symptoms.<ref name="Morales Jackson Lipworth Donnan 2014 pp. 779–786"/><ref name="Salpeter Ormiston Salpeter p=715">{{cite journal | vauthors = Salpeter SR, Ormiston TM, Salpeter EE | title = Cardioselective beta-blockers in patients with reactive airway disease: a meta-analysis | journal = Annals of Internal Medicine | volume = 137 | issue = 9 | pages = 715–725 | date = November 2002 | pmid = 12416945 | doi = 10.7326/0003-4819-137-9-200211050-00035 | publisher = American College of Physicians | doi-access = free }}</ref> [[β2-agonist]]s can somewhat mitigate β-blocker-induced [[bronchospasm]] where it exerts greater efficacy on reversing ''selective'' β-blocker-induced bronchospasm than the ''nonselective'' β-blocker-induced worsening asthma and/or COPD.<ref name="Morales Jackson Lipworth Donnan 2014 pp. 779–786">{{cite journal | vauthors = Morales DR, Jackson C, Lipworth BJ, Donnan PT, Guthrie B | title = Adverse respiratory effect of acute β-blocker exposure in asthma: a systematic review and meta-analysis of randomized controlled trials | journal = Chest | volume = 145 | issue = 4 | pages = 779–786 | date = April 2014 | pmid = 24202435 | doi = 10.1378/chest.13-1235 | publisher = Elsevier BV }}</ref>

==== Diabetes mellitus ====
Epinephrine signals early warning of the upcoming [[hypoglycemia]].<ref name="Sprague Arbeláez 2011 pp. 463–475">{{cite journal | vauthors = Sprague JE, Arbeláez AM | title = Glucose counterregulatory responses to hypoglycemia | journal = Pediatric Endocrinology Reviews | volume = 9 | issue = 1 | pages = 463–475 | date = September 2011 | pmid = 22783644 | pmc = 3755377 }}</ref>

Beta blockers' inhibition on epinephrine's effect can somewhat exacerbate hypoglycemia by interfering with [[glycogenolysis]] and mask signs of hypoglycemia such as tachycardia, palpitations, [[diaphoresis]], and tremors. Diligent blood glucose level monitoring is necessary for a patient with diabetes mellitus on beta blockers.

==== Hyperthyroidism ====
Abrupt withdrawal can result in a [[thyroid storm]].<ref name="Wyeth Propranolol" />

==== Bradycardia or AV block ====
Unless a pacemaker is present, beta blockers can severely depress conduction in the AV node, resulting in a reduction of heart rate and cardiac output. One should be very cautious with the use of beta blockers in tachycardia patients with Wolff-Parkinson-White Syndrome, as it can result in life-threatening arrhythmia in certain patients. By slowing the conduction through the AV node, preferential conduction through the accessory pathway is favored. If the patient happens to develop atrial flutter, this could lead to a 1:1 conduction with very fast ventricular rate, or worse, ventricular fibrillation in the case of atrial fibrillation.{{citation needed|date=October 2023}}