What precautions should be taken before taking propranolol (beta blocker)?

Precautions Before Taking Propranolol

Before initiating propranolol, you must screen for absolute contraindications including second or third-degree heart block, decompensated heart failure, asthma or obstructive airway disease, cardiogenic shock, sinus bradycardia, hypotension, and hypersensitivity to the drug. 1, 2, 3

Mandatory Pre-Treatment Assessment

Cardiovascular Screening

• Measure baseline heart rate and blood pressure - hold propranolol if heart rate is below 60 bpm with symptoms or systolic blood pressure is below 100 mmHg 2
• Perform cardiovascular examination with cardiac auscultation to detect heart failure signs (rales, S3 gallop, peripheral edema) 2
• Obtain electrocardiography particularly in younger infants, those with low heart rate, or those with abnormal cardiac examination findings 1
• Consider cardiology consultation if there is family history of congenital heart disease, though pretreatment cardiac screening appears of limited value in patients with unremarkable cardiac history and examination 1

Respiratory Assessment

• Screen for history of bronchospasm, asthma, or reactive airway disease - these are absolute contraindications to propranolol 2, 3
• Auscultate lungs for wheezing or evidence of obstructive airway disease 1

Metabolic Screening

• Assess for diabetes or history of hypoglycemic episodes - propranolol masks symptoms of hypoglycemia and is contraindicated in patients with recent or ongoing hypoglycemic episodes 2, 3
• Screen for hepatic or renal impairment as propranolol should be used with caution in these patients 3

Critical Drug Interactions to Review

Cardiac Medications

• Avoid combination with non-dihydropyridine calcium channel blockers (diltiazem, verapamil) - this significantly increases risk of bradycardia, hypotension, high-degree heart block, and heart failure 2, 3
• Exercise caution with digitalis glycosides - both slow AV conduction and increase bradycardia risk 3
• Review antiarrhythmic use - propafenone has additive negative inotropic effects, quinidine increases propranolol concentration and may cause postural hypotension, amiodarone has additive chronotropic effects 3
• Check for lidocaine use - propranolol reduces lidocaine clearance and increases toxicity risk 3

Other Medications

• Assess alcohol consumption - concomitant use increases propranolol plasma levels 3
• Review medications affecting CYP2D6, 1A2, or 2C19 pathways - these can alter propranolol efficacy and toxicity 3

Special Population Considerations

Pediatric Patients (Infantile Hemangioma)

• Consider inpatient hospitalization for initiation in infants 8 weeks or younger, preterm infants less than 48 weeks postconceptional age, those with poor social support, or those with cardiac/pulmonary risk factors 1
• Reduce hypoglycemia risk by administering propranolol and feeding at intervals not exceeding 8 hours (or 6 hours in younger infants) 1

Patients with Acute Illness

• Closely monitor or temporarily reduce dosing in children with any acute illness, especially those interfering with normal oral intake or associated with vomiting or diarrhea 1

Laboratory Monitoring Considerations

While routine blood work is not required before starting propranolol in otherwise healthy adults 2, be aware that:

• Propranolol may elevate serum potassium, serum transaminases, and alkaline phosphatase in hypertensive patients 3
• Blood urea nitrogen may increase in severe heart failure patients 3
• Propranolol interferes with glaucoma screening tests - inform patients that withdrawal may lead to return of increased intraocular pressure 3

Critical Safety Warnings

Allergy History

• Screen for history of severe anaphylactic reactions - patients with such history may be more reactive to repeated allergen challenge while on beta-blockers and may be unresponsive to usual epinephrine doses 3

Withdrawal Risk

• Never abruptly discontinue propranolol after chronic use - this can precipitate rebound hypertension, tachycardia, or angina 2, 4
• Plan for gradual taper over 1-3 weeks when discontinuation is necessary 1

Common Pitfalls to Avoid

• Do not assume cardiac screening is unnecessary - while extensive testing may not be needed in low-risk patients, baseline heart rate, blood pressure, and cardiac examination are mandatory 2
• Do not overlook mild asthma - even dose-related asthma is a relative contraindication, though some patients may tolerate therapy 5
• Do not ignore cardiomegaly - all patients with cardiothoracic ratio greater than 0.5 developed heart failure within 3 years in one study 5
• Do not forget to assess for cardiogenic shock risk factors in post-MI patients - propranolol may increase this risk 5, 6