Dextran 70, a high–molecular-weight polysaccharide with an average molecular weight of 70,000, is used as a plasma volume expander in clinical settings such as hypovolemia, shock, or during surgery. Its history is marked by its effectiveness in increasing intravascular volume and improving tissue perfusion, but also by potential allergic or coagulopathic reactions, which led to careful monitoring protocols during administration. Dextran 70 was developed to provide a safer and more predictable colloid solution, and it is commonly included in fluid management strategies in hospitals. Its development included rigorous clinical studies to optimize molecular weight distribution, reduce adverse reactions, and allow controlled early use under medical supervision.
BRAND NAMES
Macrodex – widely used internationally for plasma volume expansion.
Rheomacrodex – available in some European countries.
Gentran 70 – less common, regional use.
MECHANISM OF ACTION
Dextran 70 acts as a colloid plasma volume expander by increasing the oncotic pressure within the intravascular compartment. When administered intravenously, its large polysaccharide molecules remain largely in the bloodstream, drawing water from the interstitial and intracellular spaces into the circulation.
PHARMACOKINETICS
Absorption
Dextran 70 is administered exclusively by intravenous infusion, so it has complete bioavailability immediately upon administration. Because it is a large, water-soluble polysaccharide, it does not undergo absorption via the gastrointestinal tract.
Distribution
Dextran 70 has a small volume of distribution, primarily confined to the intravascular compartment due to its large molecular size (approximately 70,000 Da). Only a minor fraction distributes into the interstitial space.
Metabolism
Dextran 70 is partially metabolized by plasma and tissue dextranases, enzymes that hydrolyze the large polysaccharide molecules into smaller fragments. These smaller fragments are more readily filtered by the kidneys and eliminated in the urine.
Elimination
Dextran 70 is primarily eliminated through the renal route as intact molecules or partially metabolized fragments. The rate of excretion depends on molecular size and kidney function, with smaller fragments being cleared more rapidly.
PHARMACODYNAMICS
Dextran 70 exerts its pharmacodynamic effects primarily through intravascular volume expansion. Its large polysaccharide molecules remain largely within the bloodstream, increasing colloid osmotic pressure and drawing fluid from the interstitial and intracellular spaces into the circulation.
ADMINISTRATION
Dextran 70 is administered exclusively by intravenous infusion under controlled clinical settings. It is typically given slowly, with careful monitoring of blood pressure, heart rate, and fluid status to avoid complications such as fluid overload or hypotension.
DOSAGE AND STRENGTH
Dextran 70 is available as an intravenous solution, typically at a concentration of 6% (60 g/L) in 0.9% sodium chloride or 5% glucose solution. The usual adult dose for plasma volume expansion ranges from 500 mL to 1,000 mL per day, depending on the patient’s clinical condition, blood volume, and hemodynamic status.
DRUG INTERACTIONS
Dextran 70 can interact with several medications and physiological processes due to its effects on blood volume, coagulation, and renal clearance. Concomitant use with anticoagulants or antiplatelet agents may increase the risk of bleeding because dextran can inhibit platelet function and reduce clot formation.
FOOD INTERACTIONS
Dextran 70 is administered exclusively by intravenous infusion, so food intake has no effect on its absorption, distribution, or efficacy. Its pharmacokinetics and plasma-expanding effects remain consistent regardless of meals, allowing administration in critically ill or fasting patients without concern for timing relative to food.
CONTRAINDICATIONS
Dextran 70 is contraindicated in patients with a known hypersensitivity to dextran or any component of its formulation. It should not be used in individuals with severe renal impairment, as reduced clearance may lead to accumulation and fluid overload. Additional contraindications include congestive heart failure, pulmonary edema, or hypervolemia, where plasma volume expansion could worsen cardiovascular or pulmonary status.
SIDE EFFECTS
Hypersensitivity reactions (rash, itching, or anaphylaxis in rare cases)
Fluid overload leading to edema or pulmonary congestion
Hypotension if infused too rapidly
Nausea and vomiting
Fever or chills
Coagulopathy (impaired platelet function, increased bleeding risk)
Renal impairment in patients with pre-existing kidney disease.
OVER DOSAGE
Overdosage of dextran 70 can lead to fluid overload, pulmonary edema, hypotension, and cardiovascular strain, especially in patients with compromised heart or kidney function. Excessive plasma expansion may also exacerbate coagulopathy due to impaired platelet function.
TOXICITY
Dextran 70 exhibits dose-dependent toxicity, primarily related to its volume-expanding and anticoagulant properties. Excessive or rapid administration can lead to fluid overload, pulmonary edema, hypotension, and cardiovascular stress, particularly in patients with heart or kidney impairment. Its effect on platelet function and coagulation can increase the risk of bleeding, especially when combined with anticoagulants.
