Cyclophosphamide

CYTOXAN

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Pronunciation: sye-kloe-FOS-fa-mide

Cyclophosphamide ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Cyclophosphamide ballicule

Cyclophosphamide CYTOXAN mascot mnemonic cartoon — Visual mnemonic: Cyclophosphamide mascot
**“Cycling fossil might (be a) Cytotoxin”**
DNA alkylator → phosphoramide mustard
acrolein → hemorrhagic cystitis (prevent with mesna)

What it isAlkylating prodrug used for malignancy, vasculitis, and organ-threatening autoimmune disease.

Why this oneIts unusual reach spans curative chemotherapy and rapid control of severe autoimmune disease.

What limits it⚑ Acrolein causes hemorrhagic cystitis; urotoxic regimens require mesna and hydration. Cumulative exposure risks infertility and bladder cancer.

Cyclophosphamide molecular structure (skeletal formula) — Molecular structure: Cyclophosphamide

FDA-approved for

cancer (1959)

FDA label

Read the full label on DailyMed ↗

FDA dosing	Population	Start	Target	Max
Malignant diseases (initial & maintenance)	Adults & pediatrics	1–5 mg/kg QD
Minimal change nephrotic syndrome	Pediatrics	2 mg/kg QD × 8–12 wk		cumulative 168 mg/kg

Renal Monitor for toxicity in moderate–severe renal impairment (CrCl 10–24 mL/min); increased plasma levels/toxicity expected

Hepatic Severe hepatic impairment: reduced conversion to active metabolite, potentially reduced efficacy

Treatment beyond 90 days increases probability of sterility in males

Instructions

Take in the morning with adequate fluids to force diuresis (reduce urinary tract toxicity)
Swallow whole; do not chew or crush
Cytotoxic drug — avoid exposure to broken tablets

Available strengths

tab 25, 50 mg
inj 500, 1000, 2000 mg
cap 25, 50 mg

Contraindications

Urinary outflow obstruction

Cautions

Myelosuppression, immunosuppression, bone marrow failure and serious/fatal infections
Hemorrhagic cystitis and urinary/renal toxicity
Cardiotoxicity (myocarditis, arrhythmias, CHF)
Pulmonary toxicity (pneumonitis, fibrosis)
Secondary malignancies
Veno-occlusive liver disease
Embryo-fetal toxicity
Impaired fertility
Hyponatremia / SIADH-like syndrome

Adverse reactions

Neutropenia, febrile neutropenia
Fever
Alopecia
Nausea, vomiting, diarrhea

Pregnancy Can cause fetal harm (malformations, miscarriage, growth retardation); use effective contraception

Lactation Do not breastfeed during treatment and for 1 week after last dose

Cost

Cyclophosphamide (CYTOXAN)

Strength		#/mo	CostPlus
25 mg	tab	30 qd	not offered
50 mg	tab	30 qd	not offered
500 mg	inj	per unit	not offered
1000 mg	inj	per unit	not offered
2000 mg	inj	per unit	not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Cyclophosphamide is administered under clinical supervision and dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Generic entry1982

NO BOXED WARNINGS

Principal riskHemorrhagic cystitis; mesna and hydration are mandatory

Classes and tags

Clinical profile

Therapeutic safety burden4 / 4

Overdose danger3 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk4 / 4

Legacy pregnancy categoryD

Defining liabilityMyelosuppression, hemorrhagic cystitis, infertility, malignancy and organ toxicity.

Active metabolites

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Memory aids: interaction avatars

CYP2B6 substrate

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