Carvedilol dosage

Advise patients that initiation of treatment and (to a lesser extent) dosage increases may be associated with transient symptoms of dizziness or lightheadedness (and rarely syncope) within the first hour after dosing. Thus, during these periods, avoid situations such as driving or hazardous tasks, where symptoms could result in injury. In addition, vasodilatory symptoms often do not require treatment, but it may be useful to separate the time of dosing of carvedilol from that of the ACE inhibitor or to temporarily reduce the dose of the ACE inhibitor. Do not increase the dose of carvedilol until symptoms of worsening heart failure or vasodilation have been established. 

In clinical trials, carvedilol caused bradycardia in about 2% of patients. If pulse rate drops below 55 beats/min, reduce the dosage. 

Finally, the toxicity of some effective drugs prevents their use at maximally effective dosage. The widespread indiscriminate use of 3 blockers has been criticized because several large clinical trials indicate that some members of the group, eg, metoprolol and carvedilol, have a greater benefit than others, eg, atenolol. However, all 3 blockers appear to have similar benefits in reducing mortality after myocardial infarction, so these drugs are particularly indicated in patients with an infarct and hypertension. 

Carvedilol, like labetalol, is administered as a racemic mixture. The S(-) isomer is a nonselective B-adrenoceptor blocker, but both S(-) and R(+) isomers have approximately equal E-blocking potency. The isomers are stereoselectively metabolized in the liver, which means that their elimination half-lives may differ. The average half-life is 7-10 hours. The usual starting dosage of carvedilol for ordinary hypertension is 6.25 mg twice daily. Carvedilol reduces mortality in patients with heart failure and is therefore particularly... 

A 69-year-old woman developed confusion and paranoia over several days. She was taking carvedilol 12 mg bd, warfarin 2 mg/day, folic add 1 mg/day, levothyroxine 100 micro-grams/day, pantoprazole 40 mg/day, paroxetine 40 mg/day, and flecainide 100 mg bd. The flecainide had been started 2 weeks before. The plasma flecainide concentration was 1.36 mg/1. Paroxetine was withdrawn and the dosage of flecainide was reduced to 50 mg bd. Her delirium resolved 3 days later. 

A restrospective study of 23 patients with heart failure who could not increase the dosage of carvedilol (mean dose 5.60 3.43 mg) because of dizziness or hypotension was carried out [26 ]. Six months after switching to bisoprolol, all 13 patients with dizziness and 9 of 16 patients with hypotension were relieved of adverse symptoms. 

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