THERAPEUTICS

Brands

• Formula Q, Legatrin, Qualaquin

Generic?

• Yes

Class

• Neuromuscular drug

Commonly Prescribed for

(FDA approved in bold)

• Malaria

• Symptomatic myotonia (myotonia congenita, myotonic dystrophy)

• Leg cramps

• Congenital myasthenic syndrome

How the Drug Works

• Quinine has several actions on skeletal muscle. Increases the refractory period by acting on the muscle membrane and sodium channel, decreases motor end-plate excitability, and affects the distribution of calcium within the muscle fiber

How Long Until It Works

• 1–2 hours

If It Works

• Continue to use

If It Doesn't Work

• Change to an alternative agent

Best Augmenting Combos for Partial Response or Treatment-Resistance

• Myotonia: AEDs, such as phenytoin and carbamazepine, are effective. The antiarrhythmic drug mexiletine (also a sodium channel blocker) is an alternative

Tests

• Obtain baseline ECG due to risk of cardiac arrhythmia (common in myotonic dystrophy)

ADVERSE EFFECTS (AEs)

How the Drug Causes AEs

• Drug effect of blocking sodium channels

Notable AEs

• “Cinchonism” is a common set of AEs seen in most patients; includes headache, flushing, vertigo, hearing difficulties, tinnitus, blurry vision, and nausea. More severe symptoms include vomiting, abdominal pain, deafness, and blindness

• Hypersensitivity reactions include flushing, pruritus, rash, fever, tinnitus, and dyspnea

• Chest pain, orthostatic hypotension, hypoglycemia, anorexia, jaundice, and abnormal liver function tests

Life-Threatening or Dangerous AEs

• Cardiac arrhythmias, including AV block, atrial fibrillation, QTc prolongation, ventricular fibrillation, ventricular tachycardia, torsade de pointes, and cardiac arrest

• Hemolysis associated with glucose-6- phosphate dehydrogenase deficiency

• Severe hypersensitivity (angioedema)

• Rarely asthma or pulmonary edema

Weight Gain

• Unusua

Sedation

• Unusual

What to Do About AEs

• Lower dose for most AEs, but discontinue for serious AEs

Best Augmenting Agents to Reduce AEs

• Most AEs cannot be reduced by an augmenting agent