QiWei
QiWei Uses, Dosage, Side Effects, Mechanism of Action, How Long Does it Take to Work? QiWei is a brand name. Its generic name is Phentolamine.
QiWei
QiWei (also known as Regitine) is a non-selective, competitive α-adrenergic receptor blocker which is commonly used to treat hypertension. It is also used in the treatment of local anesthetic systemic toxicity (LAST), cold-induced vasospasm and vasospastic gangrene.
Uses for QiWei
QiWei is used to treat high blood pressure, control drug- or adrenaline-induced hypertension, treat severe hypertensive episodes due to an adrenergic agent, prevent and treat hypertensive crisis and lastly to help control cases of pheochromocytoma. It is also used in combination with an intra-arterial vasoconstrictor (like epinephrine) for the treatment of vasospastic gangrene and local anesthetic systemic toxicity (LAST).
Mechanism of Action
QiWei competitively binds to α-adrenergic receptors, resulting in smooth muscle relaxation. This results in an increase in cardiac output and a decrease in heart rate. It also reduces peripheral vascular resistance, resulting in a decrease in blood pressure. Additionally, the drug has a direct vasodilator effect to decrease blood pressure by decreasing peripheral vascular resistance.
How long does it take to work?
The effect of QiWei can be noticed within minutes of administration, with a peak effect being seen within one hour. After the peak effect has been reached, the duration of action of QiWei can range from 4 to 6 hours.
Absorption
QiWei is rapidly and almost completely absorbed by the gastrointestinal tract. Approximately 70% of the drug is found in the plasma after oral administration.
Route of Elimination
QiWei is rapidly eliminated, primarily by the kidneys. Approximately 95% of the drug is eliminated within 10 hours after oral administration.
Dosage and Administration
The recommended daily dosage of phentolamine is 5 mg to 10 mg orally three times a day. Alternatively, the drug can be administered either intramuscularly or intravenously at a dose of 2 mg to 5 mg. Intramuscular administration should be given slowly over 1 minute. Intravenous administration should be given slowly over 2 to 5 minutes.
Side Effects
Common side effects of QiWei include headache, dizziness, fatigue, nausea, vomiting, abdominal pain, diarrhea, and rash. Other serious side effects include rapid or irregular heartbeat, chest pain, difficulty breathing, severe hypotension, and changes in vision.
Toxicity
High doses of QiWei may cause respiratory depression, bradycardia, hypotension, cardiogenic shock, and pulmonary edema. Prolonged use of study drug may lead to tolerance and physical dependence.
Precaution
QiWei should be used cautiously in patients with hypotension, bradycardia, impaired renal or hepatic function, congestive heart failure, diabetes mellitus, myasthenia gravis, and electrolyte imbalance.
Interaction
QiWei may interact with other drugs, such as anticoagulants, diuretics, antihypertensives, digitalis, and beta-blockers. Discontinue use of any of these drugs if irritation or other adverse reactions occur.
Disease Interaction
QiWei may interact with certain medical conditions including anemia, atherosclerosis, Raynaud's syndrome, and thrombophlebitis. Patients with these conditions should use the drug with caution and under the supervision of a physician.
Drug Interaction
QiWei may interact with other drugs such as potassium replacement agents, barbiturates, opioids, adrenergic agents, and diuretics. Patients taking these medications should use the drug with caution and under the supervision of a physician.
Food Interactions
The absorption of QiWei may be decreased when taken with food, so it is suggested that QiWei be taken on an empty stomach with plenty of water.
Pregnancy Use
QiWei should not be used during pregnancy. Patients who are pregnant should use the drug with caution and only under the supervision of a physician.
Lactation Use
QiWei should not be used during lactation. Patients who are lactating should use the drug with caution and only under the supervision of a physician.
Acute Overdose
Symptoms of QiWei overdose include slow or irregular heartbeat, chest pain, difficulty breathing, fainting, nausea, vomiting, increased sweating, and seizures. Treatment of an overdose should be prompt medical attention.
Contraindication
QiWei should not be used in patients with hypersensitivity to the drug or any of its components. Patients who are pregnant or lactating, have cardiac arrhythmias or CHF, and those taking drugs or herbal products should use the drug with caution.
Use Direction
QiWei should be taken as directed by a healthcare professional. Take the drug with a full glass of water. Do not crush, chew, or break the extended-release tablet. Swallow the tablets whole. The tablet should be taken on an empty stomach, 1 hour before or 2 hours after meals.
Storage Condition
QiWei should be stored at room temperature, away from light, moisture, and heat. Keep the drug away from children and pets.
Volume of Distribution
The volume of distribution of QiWei is 0.5 to 0.8 L/kg.
Half Life
The half-life of QiWei is approximately 3 to 5 hours.
Clearance
The clearance of phentolamine is approximately 0.2 to 0.4 L/hr/kg.
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