Bisoprolol

PHARMACOKINETICS

Absorption

Bisoprolol is well absorbed orally, with a bioavailability of approximately 90–100%. Peak plasma concentrations are usually reached within 2–4 hours after ingestion.

Distribution

The drug has a volume of distribution (Vd) of about 3.5–5 L/kg and is moderately bound to plasma proteins (~30%).

Metabolism

Bisoprolol is partially metabolized in the liver by CYP2D6.

Excretion

Approximately 50% of the dose is excreted unchanged in the urine, while the remainder is eliminated as metabolites.

PHARMACODYNAMICS

Bisoprolol is a highly selective beta-1 adrenergic receptor blocker that exerts its effects by inhibiting the action of epinephrine (adrenaline) and norepinephrine on the heart and kidneys. Its primary pharmacodynamic actions result from this selective beta-1 receptor blockade.

DOSAGE AND ADMINISTRATION

• Route: Oral Administration

• Hypertension/Angina: 5–10 mg once daily; maintenance 5–20 mg/day based on response

• Heart Failure: Start 1.25 mg once daily, titrate gradually every 1–2 weeks up to 10 mg/day

• Timing: Take bisoprolol consistently at the same time every day, either with or without food.

• Monitoring: Adjust dose according to blood pressure, heart rate, and heart failure symptoms

• Special considerations: Modify dose in renal or hepatic impairment and in elderly patients

DRUG INTERACTIONS

• Other antihypertensives: May have additive effects, increasing the risk of hypotension or bradycardia.

• Calcium channel blockers (verapamil, diltiazem): Can cause excessive bradycardia, AV block, or heart failure.

• Antiarrhythmics (amiodarone, digoxin): Increased risk of slow heart rate and conduction abnormalities.

• Insulin or oral antidiabetics: May mask symptoms of hypoglycemia (e.g., tachycardia).

• NSAIDs: Can reduce antihypertensive effect of bisoprolol.

• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): May increase bisoprolol plasma levels, enhancing effects.

FOOD INTERACTIONS

Bisoprolol has minimal direct food interactions, but alcohol, caffeine, and excessive potassium-rich foods (e.g., bananas, unless recommended) should be limited, as they may increase dizziness or reduce the drug’s effectiveness. Additionally, diets high in sugar, sodium, or rich/spicy foods can worsen heart conditions. The medication can be taken with or without food, though some patients prefer taking it after meals to help reduce side effects such as dizziness.

CONTRAINDICATIONS

Bisoprolol is contraindicated in individuals with a known allergy to the drug, cardiogenic shock, severe heart failure, specific types of heart block, marked bradycardia, severe asthma, or metabolic acidosis.

SIDE EFFECTS

• Excessive tiredness, weakness, or fatigue.

• Dizziness or lightheadedness (especially when standing up).

• Headache.

• Coldness or numbness in fingers or toes (poor circulation to hands and feet).

• Gastrointestinal effects: May include nausea, vomiting, diarrhea, or constipation.

• Sleep disturbances, insomnia, or nightmares.

• Runny nose, cough, or sore throat.

• Muscle or joint pain.

• Dry mouth.

• Sexual side effects: Can include erectile dysfunction or reduced libido.

OVERDOSE

• Slow or irregular heartbeat (bradycardia).

• Low blood pressure (hypotension), leading to severe dizziness or fainting.

• Difficulty breathing or wheezing due to airway constriction (bronchospasm).

• Confusion or other changes in mental status, potentially leading to coma.

• Extreme fatigue and weakness.

• Swelling of the hands, feet, ankles, or lower legs (signs of heart failure).

• Cold sweats and clammy, pale skin.

• Low blood sugar (hypoglycemia), which may not present with typical early warning signs like a rapid pulse.

• Seizures.

TOXICITY

Bisoprolol toxicity results from ingestion of an excessive dose, causing an exaggeration of its normal effects on the heart and blood pressure. This can be a life-threatening condition that requires prompt medical attention.