Dr Sharon Rees @reesprescribe
Day 1: #quetiapine is a derivative of the 2nd generation atypical antipsychotic clozapine, with a superior side-effect profile. Developed in the 80s/90s, #quetiapine was approved for schizophrenia in 1997, then bipolar disorder in 2008. Licensed for adults; it also has antidepressant activity.
Dr Sharon Rees @reesprescribe
Day 2: Immediate and m.r tablet options for schizophrenia titrated to desired response; 300-450 mg twice/day or up to 800 mg m.r once/day. Bipolar mania 400-800 mg x2/day or 400-800 mg m.r once/day. Bipolar depression 300 mg o.d. Bipolar mania and depression 300-800 mg daily (divided doses or once/day).
Dr Sharon Rees @reesprescribe
Day 2 (cont); Unlicensed use as low dose #quetiapine for psychosis in Parkinson's disease (first-line option). All dosing is lower in the elderly because clearance is 30-50% lower than for adults 18-65 yrs. Oral suspension is available.
Dr Sharon Rees @reesprescribe
Day 3: Kinetics #quetiapine - Oral formulations only. High absorption/bioavailability and moderate volume of distribution. Hepatic metabolism with an active metabolite ‘norquetiapine’ formed via CYP3A4 breakdown. ¾ renal excretion; mostly inactive. T½ 7hrs, but longer for the metabolite ~12 hrs. Reduce dose if hepatic impairment.
Dr Sharon Rees @reesprescribe
Day 4: #quetiapine modulates multiple central neurotransmitter systems including serotonin, dopamine, noradrenaline and histamine. Quetiapine has a high affinity for serotonin (5HT2) and dopamine (D2) receptors, with greater 5HT2 receptor blockade relative to D2 blockade; this is believed relevant to fewer extrapyramidal effects eg dystonia, BUT akathisia is ‘common’, especially in early stages of treatment-may prevent dose increase.
Dr Sharon Rees @reesprescribe
Day 5: Common ADEs #quetiapine: fatigue, insomnia, erectile dysfunction, dysarthria, neutropenia, suicidal ideation, increased prolactin levels. Serious/rare; hypersensitivity/SCARs, pancreatitis, VTE (NOT exhaustive). Moderate risk among the atypical anti-psychotics for weight gain, driven (at least in part) by metabolic changes and anti-histamine activity.
Dr Sharon Rees @reesprescribe
Day 5 (cont): #quetiapine must be tapered gradually to reduce the risk of relapse or withdrawal syndrome. Interaction with muscarinic receptors is higher for metabolite; this can cause constipation, dry mouth etc.
Dr Sharon Rees @reesprescribe
Day 6: Drug-drug interactions for #quetiapine are mostly ‘moderate’. ‘Severe’ arise from enzyme inhibition from drugs such as protease inhibitors, clarithromycin, azole antifungals, grapefruit juice all leading to increased exposure. Lithium increases neurotoxicity. NOT exhaustive.
Dr Sharon Rees @reesprescribe
Day 7: There is a caution for #quetiapine where history/problems with drug/alcohol abuse, as #quetiapine can lower anxiety, with some sedative effects. Further, this is reported as an abuse issue in prisons. This caution is stated in SPC and patient.info, but not in the BNF.
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In addition to the tweets, read the BNF section treatment summary on psychoses and related disorders and the monograph on quetiapine and then answer the 10 questions. Please submit the answers to reesprescribe@gmail.com as a numbered list with TRUE/FALSE or the correct A, B, C, D option. If you achieve 8 or more out of ten on the questions, a CPD certificate will be emailed to you.
Further reading on #quetiapine
- Psychoses and related disorders : https://bnf.nice.org.uk/treatment-summary/psychoses-and-related-disorders.html
- Quetiapine 300 mg film-coated tablets : https://www.medicines.org.uk/emc/product/8252/smpc#gref
Quetiapine is related to first-generation antipsychotics like haloperidol
TRUE or FALSE?
Quetiapine has a better side-effect profile compared to clozapine
TRUE or FALSE?
Which is NOT an advantage of quetiapine compared to clozapine?
- Less extra pyramidal symptoms
- Low hyperprolactinaemia risk
- Less dystonia
- No drug-drug interactions
Quetiapine dosing is likely to be reduced if there is hepatic impairment, or for use in the elderly
TRUE or FALSE?
Which of the following is TRUE?
- Quetiapine has an active metabolite which also causes side-effects
- Quetiapine has a low oral bioavailability
- Quetiapine has 100% renal excretion of active drug
- Quetiapine undergoes mainly phase 2 metabolism
The primary mechanism of action for quetiapine is via blockade of several dopamine receptors
TRUE or FALSE?
One reason why quetiapine has less extra pyramidal symptoms is because there is a higher ratio of serotonin to dopamine blockade TRUE or FALSE?
Which of the following is a common adverse drug event for quetiapine?
- Severe cutaneous adverse reactions (SCARs)
- Pancreatitis
- Erectile dysfunction
- VTE
Several drug groups eg azole antifungals can inhibit the breakdown of quetiapine leading to a risk of toxicity
TRUE or FALSE?
Quetiapine may be used in a drug abuse capacity
TRUE or FALSE?