Cyclophosphamide exerts its cytotoxic effects primarily through alkylation of DNA. This process disrupts DNA replication and cell division, leading to cell death, particularly in rapidly proliferating cells like cancer cells. The drug itself is a prodrug; it requires metabolic activation to its active metabolites, primarily phosphoramide mustard and acrolein.
Metabolic Activation
Cytochrome P450 enzymes in the liver metabolize cyclophosphamide to 4-hydroxycyclophosphamide. This crucial step is followed by spontaneous ring opening, yielding aldophosphamide, which then breaks down into the active alkylating agent, phosphoramide mustard. Simultaneously, acrolein, a toxic metabolite responsible for some of cyclophosphamide’s side effects (like hemorrhagic cystitis), is formed. Individual variations in the activity of these enzymes can influence drug efficacy and toxicity.
Drug Elimination
The body eliminates cyclophosphamide and its metabolites primarily through the kidneys. This excretion largely occurs through glomerular filtration and tubular secretion. Impaired renal function can significantly impact the elimination process, increasing the risk of drug accumulation and toxicity. Careful monitoring of renal function is thus critical during cyclophosphamide therapy. Appropriate hydration is recommended to minimize the risk of hemorrhagic cystitis due to acrolein.
