Clozapine

Aka: Clozapine, Clozaril

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II. Mechanism

  1. Atypical Antipsychotic (Second Generation agent)
  2. Neuroleptic
  3. Dibenzodiazepine Antipsychotic
  4. Blocks Dopamine receptors
  5. Blocks Cholinergic and adrenergic neurotransmission
  6. Blocks Serotonin and Histamine neurotransmission

III. Precautions

  1. Not a first line Antipsychotic: See Disadvantages below
  2. Only providers in Clozapine REMS Program can prescribe
    1. Each patient on Clozapine must be registered with the program
    2. Requires regular submission of Absolute Neutrophil Counts
  3. FDA black box warnings
    1. Agranulocytosis
    2. Seizure risk, Myocarditis
    3. Orthostatic Hypotension
    4. Increased mortality in elderly

IV. Indications

  1. Schizophrenia refractory to other agents
  2. Suicidal behavior in Schizophrenia
  3. Psychosis in the elderly (not FDA approved)
  4. Bipolar Disorder (not FDA approved)

V. Dosing

  1. If doses are missed >48 hours, retitrate up to prior dose (risk of Orthostatic Hypotension)
  2. Adults
    1. Initial: 12.5 mg orally daily to twice daily
    2. Titrate slowly upwards in increments of 25-50 mg/day over 2 weeks
    3. Target dosing: 300 to 450 mg/day
    4. Maximum dose: 900 mg/day
  3. Elderly
    1. Initial: 6.5 orally daily
    2. Titrate slowly upwards in increments of 25 mg/day
    3. Maximum dose: 450 mg/day

VI. Cost

  1. Even generic costs >$200 per month

VII. Disadvantages

  1. Agranulocytosis has high mortality
  2. Higher risk of Diabetes Mellitus and weight gain
  3. Hypertriglyceridemia

VIII. Advantages

  1. Few Extrapyramidal Side Effects and no associated Tardive Dyskinesia

IX. Adverse Effects

  1. Anticholinergic Symptoms (potent antimuscarinic effects)
  2. Agranulocytosis (1 to 2% of patients)
    1. Do not start Clozapine if Absolute Neutrophil Count <1500/mm3
    2. Hold Clozapine if Absolute Neutrophil Count falls <1000/mm3
  3. Withdrawal (risk of Psychosis if abruptly stopped)
  4. Othostatic Hypotension or Syncope (alpha-Adrenergic Receptor blockade)
  5. Bradycardia or Tachycardia
  6. Hyperthermia
  7. Hyperglycemia including development of Diabetes Mellitus (common)
  8. Seizures (1 to 4% of patients, dose-related)
  9. Sialorrhea
  10. Weight gain (common)
  11. Sedation
  12. Suicidality
  13. QTc Prolongation (uncommon)
  14. Gastrointestinal hypomotility
    1. Risk of life-threatening Toxic Megacolon
    2. Use prophylactic Laxative
  15. Myocarditis (0.5 to 3%)
    1. Onset within first few weeks to month of therapy
    2. Mortality may approach 50%

X. Drug Interactions

  1. Primarily metabolized by CYP1A2 and CYP3A4 (as well as CP2D6)
  2. Anticholinergic Agent and Antihypertensive agent effects are potentiated by Clozapine
  3. Displaces Protein-bound drugs from their plasma Protein bindings
  4. Increase Antipsychotic levels (toxicity risk): Monitor for toxicity
    1. Grapefruit juice
    2. Caffeine
    3. Cimetidine
    4. Ciprofloxacin
    5. Citalopram
    6. Erythromycin
    7. Fluoxetine
    8. Fluvoxamine
    9. Paroxetine
    10. Sertraline
  5. Decrease Antipsychotic levels (lower efficacy)
    1. Barbiturates
    2. Carbamazepine
    3. Phenytoin
    4. Nicotine
    5. Rifampin

XI. Safety

  1. Pregnancy Category B
  2. Avoid in Lactation

XII. Monitoring

  1. See Antipsychotic
  2. Clozapine serum therapeutic concentration: 200 to 450 ng/ml
  3. Absolute Neutrophil Counts (ANC)
    1. Obtain weekly for the first 6 months
    2. Obtain every 2 weeks for months 6 to 12
    3. Obtain monthly thereafter
    4. Increase monitoring frequency if ANC starts to fall

XIII. Resources

  1. Clozapine REMS Program
    1. https://www.newclozapinerems.com/
  2. Clozapine (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d5c8a456-6f3c-4963-b321-4ed746f690e4

XIV. References

  1. (2015) Presc Lett 22(11): 65
  2. (2016) Med Lett Drugs Ther 58(1510): 160-5
  3. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 42-3
  4. Hamilton (2020) Tarascon Pocket Pharmacopoeia

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Cost: Medications

clozapine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
CLOZAPINE 100 MG TABLET Generic $0.57 each
CLOZAPINE 200 MG TABLET Generic $1.16 each
CLOZAPINE 25 MG TABLET Generic $0.27 each
CLOZAPINE 50 MG TABLET Generic $0.60 each
CLOZAPINE ODT 100 MG TABLET Generic $4.42 each
CLOZAPINE ODT 25 MG TABLET Generic $2.12 each
clozaril (on 6/22/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
CLOZARIL 100 MG TABLET Generic $0.57 each
FPNotebook does not benefit financially from showing this medication data or their pharmacy links. This information is provided only to help medical providers and their patients see relative costs. Insurance plans negotiate lower medication prices with suppliers. Prices shown here are out of pocket, non-negotiated rates. See Needy Meds for financial assistance information. GoodRx is another tool for finding lower drug prices.

Ontology: Clozapine (C0009079)

Definition (CHV) a drug used to treat schizophrenia
Definition (NCI) A synthetic dibenzo-diazepine derivative, atypical antipsychotic Clozapine blocks several neurotransmitter receptors in the brain (dopamine type 4, serotonin type 2, norepinephrine, acetylcholine, and histamine receptors). Unlike traditional antipsychotic agents, it weakly blocks dopamine type 2 receptors. It relieves schizophrenic symptoms (hallucinations, delusions, dementia). (NCI04)
Definition (MSH) A tricylic dibenzodiazepine, classified as an atypical antipsychotic agent. It binds several types of central nervous system receptors, and displays a unique pharmacological profile. Clozapine is a serotonin antagonist, with strong binding to 5-HT 2A/2C receptor subtype. It also displays strong affinity to several dopaminergic receptors, but shows only weak antagonism at the dopamine D2 receptor, a receptor commonly thought to modulate neuroleptic activity. Agranulocytosis is a major adverse effect associated with administration of this agent.
Definition (CSP) tricyclic dibenzodiazepine, classified as an atypical antipsychotic agent; binds several types of central nervous system receptors, and displays a unique pharmacological profile; it is a serotonin antagonist, with strong binding to 5-HT 2A/2C receptor subtype, and also displays strong affinity to several dopaminergic receptors, but shows only weak antagonism at the dopamine D2 receptor, a receptor commonly thought to modulate neuroleptic activity; agranulocytosis is a major adverse effect associated with administration of this agent.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D003024
SnomedCT 387568001, 96221003
LNC LP17236-8, MTHU004254
English 5H-Dibenzo(b,e)(1,4)diazepine, 8-chloro-11-(4-methyl-1-piperazinyl)-, clozapine, clozapine (medication), CLOZAPINE, Clozapine [Chemical/Ingredient], cloZAPine, CloZAPine, 8-Chloro-11-(4-methyl-1-piperazinyl)-5H-dibenzo(b,e)(1,4)diazepine, Clozapine, Clozapine (product), Clozapine (substance)
Swedish Klozapin
Czech klozapin
Finnish Klotsapiini
Russian LEPONEKS, KLOZAPIN, AZALEPTIN, АЗАЛЕПТИН, КЛОЗАПИН, ЛЕПОНЕКС
Japanese クロザピン
Croatian KLOZAPIN
Polish Klozapina
Spanish clozapina (producto), clozapina (sustancia), clozapina, Clozapina
French Clozapine
German Clozapin
Italian Clozapina
Portuguese Clozapina
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Clozaril (C0719386)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D003024
English clozaril, Clozaril
Derived from the NIH UMLS (Unified Medical Language System)

Related Topics in Pharmacology

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