Lidocaine chemical structure
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Xylocaine

Lidocaine (INN) or lignocaine (former BAN) is a popular local anesthetic and a derivative of cocaine (without its stimulant properties) that is often used in dentistry or topically. The most commonly encountered lidocaine preparations are marketed by AstraZeneca under the brand names Xylocaine and Xylocard, though lidocaine is also found in many other proprietary preparations. more...

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History

Lidocaine, the first amide-type local anesthetic, was developed by Nils Löfgren and Bengt Lundqvist in 1943 and first marketed in 1948.

Also used in pet medications.

Pharmacology

Lidocaine is metabolized in the liver to pharmacologically active breakdown products which are excreted by the kidneys. It is faster acting and longer lasting than procaine (Novocain).

When given intravenously, lidocaine is a class Ib antiarrhythmic agent and will block the sodium channel of the cardiac action potential, which decreases automaticity by reducing the slope of phase 4 depolarization with little effect on the PR interval, QRS complex or QT interval.

This drug is used in the treatment of ventricular cardiac arrhythmias and cardiac arrest with ventricular fibrillation, especially with acute ischemia, though it is not useful in the treatment of atrial arrhythmias.

The elimination half life of intravenous lidocaine is about 109 minutes, but because it is metabolized in the liver (which depends on liver blood flow), dosage should be reduced in patients with low cardiac output or who are in shock. In patients with cardiogenic shock, the half life may exceed ten hours.

Toxicity

Toxicity is most often seen when there has been an inadvertent intravascular injection of lidocaine when being used as a local anesthetic. Central nervous system toxicity manifests as tinnitus, dizziness, paresthesia (pins and needles), confusion and – in more severe cases – seizures or coma. Severe toxicity may also result in cardiovascular system collapse or ventricular fibrillation.

Related Information

  • Benzocaine
  • Bupivacaine
  • Procaine
  • Cocaine


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Betamethasone ineffective for rotator cuff tendinosis
From American Family Physician, 10/1/05 by Karl E. Miller

Shoulder pain is the second most common reason for time taken off work in the United States. In middle-aged adults, the primary cause of shoulder pain is degeneration of the rotator cuff tendons. This degeneration occurs as a normal part of aging, beginning with cuff tendinosis and progressing to partial- or full-thickness tears. In severe cases, it leads to massive cuff tears and osteoarthritis of the glenohumeral joint. Multiple factors play a role in developing cuff degeneration, including tension overload, primary or secondary impingement, impaired repair mechanisms, and overhead activities. Treatment of rotator cuff tendinosis includes rest, activity modification, and physical therapy. One (controversial) treatment option is corticosteroid injection. Studies demonstrate positive and negative outcomes with corticosteroid injection; however, few have used sham injections as a control. Alvarez and associates performed a randomized controlled trial of patients with chronic rotator cuff tendinosis to evaluate the efficacy of subacromial injections of betamethasone (Celestone) with lidocaine (Xylocaine) compared with lidocaine alone.

Inclusion criteria for the trial included pain in and around the shoulder or lateral deltoid area and pain performing overhead activity, with the following physical examination findings: pain on palpation of the cuff and its insertion into the proximal humorous; positive Neer impingement sign (pain when the arm is placed in full pronation and flexed against pressure); and decreased or painful range of motion. Participants were randomly assigned to subacromial posterolateral injection of 1 mL (6 mg) of betamethasone with 4 mL of 2 percent lidocaine or 5 mL of 2 percent lidocaine alone (control). The injections were given by the two principal investigators using pre-filled syringes to blind the trial. Outcome measures included a disease-specific quality-of-life index completed by each participant, standardized shoulder assessments, a Neer impingement sign evaluation, and active range of motion. Participants were evaluated at two weeks, six weeks, three months, and six months after the injection.

Sixty-two patients qualified for the study, and 58 completed it. Patients in the two groups were similar at baseline with regard to gender, age, hand dominance, duration of symptoms, Workplace Safety and Insurance Board status, and subjective and objective measurements. Both groups showed improvement in their quality-of-life scores during the study. There was no statistically significant difference between the groups in the scores for any of the outcomes at any time during the study, with the exception of active forward elevation at two weeks (148.8 [+ or -] 17.5 degrees in the betamethasone group compared with 133.3 [+ or -] 25.4 in the control group). This difference was not present at subsequent evaluations. At six months, 13 percent of the betamethasone group and 18 percent of the control group reported a "good to excellent" result.

The authors conclude that subacromial injection of betamethasone with lidocaine for six months was no more effective than lidocaine alone in the treatment of patients with chronic rotator cuff tendinosis unresponsive to nonsteroidal anti-inflammatory drugs and physical therapy. They add that despite the popularity of this intervention, they were unable to document any benefit to subacromial corticosteroid injection in these patients.

KARL E. MILLER, M.D.

Alvarez CM, et al. A prospective, double-blind, randomized clinical trial comparing subacromial injection of betamethasone and xylocaine to xylocaine alone in chronic rotator cuff tendinosis. Am J Sports Med February 2005;33:255-62.

COPYRIGHT 2005 American Academy of Family Physicians
COPYRIGHT 2005 Gale Group

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