Adverse drug reactions associated with the use of<unk> s include: nausea, diarrhea, bronchospasm, dyspnea, cold extremities, exacerbation of Raynaud's syndrome, bradycardia, hypotension, heart failure, heart block, fatigue, dizziness, alopecia (hair loss), abnormal vision, hallucinations, insomnia, nightmares, sexual dysfunction, erectile dysfunction and/or alteration of glucose and lipid metabolism. Mixed α1/β-antagonist therapy is also commonly associated with orthostatic hypotension. Carvedilol therapy is commonly associated with edema. Due to the high penetration across the blood–brain barrier, lipophilic<unk> s, such as propranolol and metoprolol, are more likely than other less lipophilic<unk> s to cause sleep disturbances, such as insomnia, vivid dreams and nightmares. Adverse effects associated with β2-adrenergic receptor antagonist activity (bronchospasm, peripheral vasoconstriction, alteration of glucose and lipid metabolism) are less common with β1-selective (often termed "cardioselective") agents, but receptor selectivity diminishes at higher doses.<unk>  blockade, especially of the<unk> -1 receptor at the macula densa, inhibits renin release, thus decreasing the release of aldosterone. This causes hyponatremia and hyperkalemia. Hypoglycemia can occur with<unk>  blockade because β2-adrenoceptors normally stimulate glycogen breakdown (glycogenolysis) in the liver and pancreatic release of the hormone glucagon, which work together to increase plasma glucose. Therefore, blocking β2-adrenoceptors lowers plasma glucose. β1-blockers have fewer metabolic side effects in diabetic patients; however, the fast heart rate that serves as a warning sign for insulin-induced low blood sugar may be masked, resulting in hypoglycemia unawareness. This is termed<unk> -induced hypoglycemia unawareness. Therefore,<unk> s are to be used cautiously in diabetics. A 2007 study revealed diuretics and<unk> s used for hypertension increase a patient's risk of developing diabetes mellitus, while ACE inhibitors and angiotensin II receptor antagonists (angiotensin receptor<unk> s) actually decrease the risk of diabetes. Clinical guidelines in Great Britain, but not in the United States, call for avoiding diuretics and<unk> s as first-line treatment of hypertension due to the risk of diabetes.<unk> s must not be used in the treatment of selective alpha-adrenergic agonist overdose. The blockade of only<unk>  receptors increases blood pressure, reduces coronary blood flow, left ventricular function, and cardiac output and tissue perfusion by means of leaving the alpha-adrenergic system stimulation unopposed.<unk> s with lipophilic properties and CNS penetration such as metoprolol and labetalol may be useful for treating CNS and cardiovascular toxicity from a methamphetamine overdose. The mixed alpha- and<unk>  labetalol is especially useful for treatment of concomitant tachycardia and hypertension induced by methamphetamine. The phenomenon of "unopposed alpha stimulation" has not been reported with the use of<unk> s for treatment of methamphetamine toxicity. Other appropriate antihypertensive drugs to administer during hypertensive crisis resulting from stimulant overdose are vasodilators such as nitroglycerin, diuretics such as furosemide, and alpha<unk> s such as phentolamine. Contraindications Contraindications for<unk> s include: * Abrupt discontinuations *Acute bronchospasm *Acute heart failure *Asthma *AV block *Bradycardia *Bronchitis *Cardiogenic shock *Cerebrovascular disease *Chronic obstructive pulmonary disease (COPD) *Diabetes mellitus *Emphysema *Hypersensitivity to<unk> s *Hypotension *Kidney failure *Hepatic disease *Myopathy *Pheochromocytoma *Psoriasis *Stroke *Vasospastic angina *Wolff–Parkinson–White syndrome Asthma The 2007 National Heart, Lung, and Blood Institute (NHLBI) asthma guidelines recommend against the use of non-selective<unk> s in asthmatics, while allowing for the use of cardioselective<unk> s. Cardioselective<unk>  (β1<unk> s), if really required, can be prescribed at the least possible dose to those with mild to moderate respiratory symptoms. β2-agonists 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. Diabetes mellitus Epinephrine signals early warning of the upcoming hypoglycemia.<unk> s' 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<unk> . Hyperthyroidism Abrupt withdrawal can result in a thyroid storm. Bradycardia or AV block Unless a pacemaker is present,<unk> s 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<unk> s in tachycardic 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. Toxicity Glucagon, used in the treatment of overdose, increases the strength of heart contractions, increases intracellular cAMP, and decreases renal vascular resistance. It is, therefore, useful in patients with<unk>  cardiotoxicity. Cardiac pacing is usually reserved for patients unresponsive to pharmacological therapy. People experiencing bronchospasm due to the β2 receptor-blocking effects of nonselective<unk> s may be treated with anticholinergic drugs, such as ipratropium, which are safer than<unk>  agonists in patients with cardiovascular disease. Other antidotes for<unk>  poisoning are salbutamol and isoprenaline.
Beta blocker
Calcium channel blocker
ACE inhibitor
Antiplatelet drug
Antidote
Channel blocker
Bronchial blocker
Mercurial diuretic