A 28-year-old man with a 4-year history of paranoid schizophrenia presents to the community mental health team. Despite trials of risperidone, olanzapine, and quetiapine at adequate doses for sufficient duration, he continues to experience persistent auditory hallucinations and delusions significantly impairing his functioning. He has been concordant with all treatments. Physical examination and baseline blood tests including FBC, U&Es, LFTs, lipids, HbA1c, and ECG are normal. What is the most appropriate next step in management?
Q92
A 36-year-old man with paranoid schizophrenia has been on clozapine 400mg daily for 18 months with good symptom control. He attends for routine blood monitoring. His results show: WBC 3.2 × 10⁹/L, neutrophils 1.4 × 10⁹/L, haemoglobin 138 g/L, platelets 245 × 10⁹/L. He is asymptomatic with no signs of infection. His previous WBC 3 weeks ago was 4.1 × 10⁹/L with neutrophils 2.1 × 10⁹/L. What is the most appropriate immediate action?
Q93
A 24-year-old woman is brought to A&E by her family. Over the past 5 days, she has become increasingly agitated, claiming she is a prophet chosen by God to save humanity. She has not slept for 72 hours, has spent £8000 on credit cards buying gifts for strangers, and attempted to break into a church to preach. She has no previous psychiatric history. Physical examination shows pulse 110 bpm, blood pressure 145/90 mmHg, temperature 37.2°C, and pupils equal and reactive. Urine drug screen is negative. What is the most appropriate initial pharmacological management?
Q94
A 53-year-old man with bipolar affective disorder type I has been maintained on lithium carbonate 800mg daily for 8 years with excellent mood stability. Recent routine blood tests show: serum creatinine 145 µmol/L (baseline 85 µmol/L), eGFR 48 ml/min/1.73m² (previously 78 ml/min/1.73m²), lithium level 0.85 mmol/L (therapeutic range 0.6-1.0), TSH 5.2 mU/L. Urine dipstick shows no proteinuria. He has no other medical conditions and takes no other regular medications. What is the most appropriate next step in management?
Q95
A 47-year-old woman with a 15-year history of paranoid schizophrenia presents to the community mental health team. She has been stable on risperidone long-acting injection 50mg fortnightly for the past 3 years. She reports new onset amenorrhoea for 6 months and occasional milky discharge from her nipples. Blood tests show prolactin level of 2800 mU/L (normal range 102-496 mU/L). She is otherwise well and wishes to continue her current treatment as she feels it controls her symptoms effectively. What is the most appropriate management?
Q96
A 52-year-old woman with a 25-year history of bipolar affective disorder has been stable on lithium carbonate 1000mg daily for 15 years. She presents for routine monitoring. Blood tests show: lithium level 0.75 mmol/L, sodium 138 mmol/L, potassium 4.0 mmol/L, urea 8.2 mmol/L, creatinine 125 μmol/L, eGFR 52 ml/min/1.73m², calcium 2.65 mmol/L (normal 2.20-2.60), PTH 8.5 pmol/L (normal 1.6-6.9), TSH 2.8 mU/L, free T4 14 pmol/L. She is clinically euthymic with no symptoms. Previous eGFR 1 year ago was 68 ml/min/1.73m². What is the most appropriate next step in management?
Q97
A 26-year-old woman presents with her first episode of psychosis. She describes a 2-month history of hearing her thoughts spoken aloud, believing that her colleagues can hear her thoughts, and experiencing her actions being controlled by an external force. She has social withdrawal and neglect of self-care. Mental state examination confirms thought echo, thought broadcasting, and passivity phenomena. There is no substance use, and medical investigations are normal. Considering the prognostic factors in first-episode psychosis, which feature in her presentation is associated with the poorest long-term outcome?
Q98
A 35-year-old man with a 10-year history of bipolar affective disorder type I is reviewed in clinic. He has had five manic episodes and three depressive episodes. He has tried lithium (stopped due to tremor), sodium valproate (stopped due to weight gain), and quetiapine (stopped due to sedation). He is currently on lamotrigine 200mg daily but has had two depressive episodes in the past year requiring admission. His current mood is stable. He consents to trying a new medication. What is the mechanism of action of lamotrigine that makes it particularly effective for bipolar depression?
Q99
A 49-year-old man with treatment-resistant paranoid schizophrenia has been on clozapine 700mg daily for 4 years. He presents with a 2-week history of worsening auditory hallucinations and persecutory delusions despite good previous response. He has been compliant with medication. He is a heavy smoker (30 cigarettes/day) but stopped smoking 3 weeks ago using nicotine patches after developing pneumonia. Clozapine level taken yesterday is 620 ng/mL (therapeutic range 350-600 ng/mL). Which pharmacokinetic interaction best explains his elevated clozapine level?
Q100
A 27-year-old woman with a 4-year history of bipolar affective disorder type I presents to the emergency department with confusion, coarse tremor, vomiting, and diarrhoea for 2 days. She has been taking lithium carbonate 1200mg daily. One week ago, her GP prescribed ibuprofen 400mg three times daily for ankle pain following a sports injury. Observations: temperature 37.8°C, pulse 95/min, BP 110/70 mmHg. Blood tests show: sodium 144 mmol/L, potassium 4.8 mmol/L, urea 12.5 mmol/L, creatinine 145 μmol/L, lithium level 1.9 mmol/L. What is the underlying mechanism causing her presentation?
Severe Mental Illness UK Medical PG Practice Questions and MCQs
Question 91: A 28-year-old man with a 4-year history of paranoid schizophrenia presents to the community mental health team. Despite trials of risperidone, olanzapine, and quetiapine at adequate doses for sufficient duration, he continues to experience persistent auditory hallucinations and delusions significantly impairing his functioning. He has been concordant with all treatments. Physical examination and baseline blood tests including FBC, U&Es, LFTs, lipids, HbA1c, and ECG are normal. What is the most appropriate next step in management?
A. Start clozapine 12.5mg daily and titrate according to protocol (Correct Answer)
B. Add aripiprazole to current antipsychotic
C. Trial of amisulpride 400mg twice daily
D. Start depot paliperidone 150mg monthly
E. Refer for cognitive behavioural therapy for psychosis
Explanation: ***Start clozapine 12.5mg daily and titrate according to protocol***- The patient meets the criteria for **treatment-resistant schizophrenia**, defined as a lack of response to at least two different antipsychotics (one being a second-generation) at adequate doses and duration.- **Clozapine** is the gold-standard treatment for resistance and must be started at a low dose with strict **Full Blood Count (FBC)** monitoring due to the risk of **agranulocytosis**.*Add aripiprazole to current antipsychotic*- Antipsychotic **polypharmacy** is generally not recommended until clozapine has been trialed alone and found to be insufficient.- Prioritizing **clozapine monotherapy** is the evidence-based next step over adding a second-generation partial agonist like aripiprazole.*Trial of amisulpride 400mg twice daily*- After failing three different antipsychotics (risperidone, olanzapine, and quetiapine), trying a fourth non-clozapine agent like **amisulpride** is unlikely to achieve clinical remission.- Guidelines emphasize that delaying clozapine in favor of multiple standard antipsychotic trials leads to poorer long-term **functional outcomes**.*Start depot paliperidone 150mg monthly*- **Long-acting injectables (LAIs)** or depots are primarily used to address issues with **treatment concordance** (adherence).- Since this patient has been **concordant** with his oral medications, the failure is pharmacological rather than behavioral, making a depot formulation inappropriate.*Refer for cognitive behavioural therapy for psychosis*- **CBTp** is a valuable adjunctive treatment but should not delay the pharmacological management of treatment-resistant symptoms with **clozapine**.- While recommended for all patients with schizophrenia, it is secondary to resolving **persistent hallucinations and delusions** that have failed multiple biological interventions.
Question 92: A 36-year-old man with paranoid schizophrenia has been on clozapine 400mg daily for 18 months with good symptom control. He attends for routine blood monitoring. His results show: WBC 3.2 × 10⁹/L, neutrophils 1.4 × 10⁹/L, haemoglobin 138 g/L, platelets 245 × 10⁹/L. He is asymptomatic with no signs of infection. His previous WBC 3 weeks ago was 4.1 × 10⁹/L with neutrophils 2.1 × 10⁹/L. What is the most appropriate immediate action?
A. Continue clozapine and repeat blood tests in 1 week
B. Stop clozapine immediately and arrange urgent haematology review
C. Continue clozapine and repeat blood tests in 3 days (Correct Answer)
D. Reduce clozapine dose to 300mg daily and repeat bloods in 1 week
E. Stop clozapine immediately and start olanzapine 20mg daily
Explanation: ***Continue clozapine and repeat blood tests in 3 days***
- The patient's **neutrophil count of 1.4 × 10⁹/L** falls into the **Amber light** monitoring category, which, in some protocols, is defined for an ANC between 1.0 and 1.5 × 10⁹/L.
- In this **Amber light** situation, clozapine treatment is continued, but monitoring frequency must be increased to at least **twice weekly** (every 3-4 days) until counts stabilize or improve.
*Continue clozapine and repeat blood tests in 1 week*
- **Weekly monitoring** is the routine frequency for stable patients in the Green light category, not for those with an Amber light result indicating a potential risk.
- Waiting a full week before rechecking bloods for an **Amber light** result could delay critical intervention if the neutrophil count continues to decline rapidly.
*Stop clozapine immediately and arrange urgent haematology review*
- **Immediate cessation** of clozapine is indicated for **Red light** results, typically when the neutrophil count drops below 1.0 × 10⁹/L or the WBC is <3.0 × 10⁹/L.
- The patient's current results do not meet these **Red light** criteria, and premature discontinuation risks a severe **psychotic relapse** in treatment-resistant schizophrenia.
*Reduce clozapine dose to 300mg daily and repeat bloods in 1 week*
- **Dose reduction** is not a recommended or evidence-based strategy for managing clozapine-induced **neutropenia**; the focus is on monitoring and cessation if thresholds are met.
- Repeating blood tests in **1 week** is insufficient for an Amber light scenario, which requires more frequent monitoring to detect any further deterioration promptly.
*Stop clozapine immediately and start olanzapine 20mg daily*
- This action is premature, as the patient's hematological parameters have not yet reached the **Red light** threshold that necessitates immediate clozapine discontinuation.
- Replacing clozapine with **olanzapine** may not be effective for a patient whose condition has been controlled by clozapine, a drug reserved for **treatment-resistant schizophrenia**.
Question 93: A 24-year-old woman is brought to A&E by her family. Over the past 5 days, she has become increasingly agitated, claiming she is a prophet chosen by God to save humanity. She has not slept for 72 hours, has spent £8000 on credit cards buying gifts for strangers, and attempted to break into a church to preach. She has no previous psychiatric history. Physical examination shows pulse 110 bpm, blood pressure 145/90 mmHg, temperature 37.2°C, and pupils equal and reactive. Urine drug screen is negative. What is the most appropriate initial pharmacological management?
A. Oral olanzapine 15mg daily (Correct Answer)
B. Oral haloperidol 5mg three times daily
C. Oral lithium carbonate 400mg twice daily
D. Intramuscular lorazepam 2mg stat
E. Oral sodium valproate 500mg twice daily
Explanation: ***Oral olanzapine 15mg daily***
- The patient presents with **acute mania with psychotic features** (grandiose delusions, reduced sleep, impulsivity); **NICE guidelines** recommend an **antipsychotic** (quetiapine, risperidone, or **olanzapine**) as first-line monotherapy.
- **Atypical antipsychotics** are preferred due to their rapid onset of action and lower risk of **extrapyramidal side effects** compared to first-generation options.
*Oral haloperidol 5mg three times daily*
- While effective for acute mania, **haloperidol** carries a significantly higher risk of **acute dystonia** and other **extrapyramidal symptoms**.
- Modern clinical practice prefers **atypical antipsychotics** over typical ones for the initial management of a first episode unless specifically contraindicated.
*Oral lithium carbonate 400mg twice daily*
- **Lithium** is highly effective for long-term maintenance but has a **slow onset of action**, typically taking 5 to 7 days to reach therapeutic effects.
- For an acute psychiatric emergency with severe symptoms, it is not used as first-line monotherapy but can be **added later** if antipsychotics are insufficient.
*Intramuscular lorazepam 2mg stat*
- **Benzodiazepines** like **lorazepam** are useful as adjunctive therapy for immediate **sedation** and behavioral control but do not treat the underlying **manic process** or psychosis.
- **Intramuscular** administration is reserved for patients refusing oral medication or requiring **rapid tranquilization** for safety; this patient is currently accepting oral options.
*Oral sodium valproate 500mg twice daily*
- **Sodium valproate** is a mood stabilizer that generally takes longer to work than antipsychotics in the **acute phase** of mania.
- It is strictly **contraindicated** in women of **childbearing potential** (unless a pregnancy prevention program is in place) due to its high **teratogenic risk**, making it an inappropriate initial choice for this 24-year-old woman.
Question 94: A 53-year-old man with bipolar affective disorder type I has been maintained on lithium carbonate 800mg daily for 8 years with excellent mood stability. Recent routine blood tests show: serum creatinine 145 µmol/L (baseline 85 µmol/L), eGFR 48 ml/min/1.73m² (previously 78 ml/min/1.73m²), lithium level 0.85 mmol/L (therapeutic range 0.6-1.0), TSH 5.2 mU/L. Urine dipstick shows no proteinuria. He has no other medical conditions and takes no other regular medications. What is the most appropriate next step in management?
A. Continue lithium and repeat renal function in 3 months
B. Reduce lithium dose to 600mg daily
C. Switch to sodium valproate 1000mg daily
D. Refer to nephrology and continue lithium pending review (Correct Answer)
E. Stop lithium immediately and switch to lamotrigine
Explanation: ***Refer to nephrology and continue lithium pending review***- NICE guidelines recommend a **nephrology referral** if the eGFR falls below **60 ml/min/1.73m²** or if there is a significant decline in renal function while on lithium.- Given the patient's **mood stability** for 8 years, lithium should not be stopped abruptly without specialist consultation to weigh the risks of **lithium nephrotoxicity** against the risk of **bipolar relapse**.*Continue lithium and repeat renal function in 3 months*- This approach is inappropriate because the **eGFR decline** (from 78 to 48) is substantial and places the patient in **Stage 3B Chronic Kidney Disease**.- Waiting three months ignores the need for a specialist evaluation to determine the cause of the **rising serum creatinine** and potential long-term damage.*Reduce lithium dose to 600mg daily*- While reducing the dose may lower serum levels, it does not address the underlying **renal impairment** that requires specialist diagnostic workup.- Adjusting the dose without expert advice may also drop levels below the **therapeutic range**, risking a **manic or depressive relapse**.*Switch to sodium valproate 1000mg daily*- Changing maintenance therapy in a stable patient is a high-risk decision that should be guided by a multidisciplinary approach involving a **nephrologist** and psychiatrist.- **Sodium valproate** is an alternative, but the immediate priority is investigating the **acute-on-chronic decline** in renal function rather than switching medication.*Stop lithium immediately and switch to lamotrigine*- Abrupt discontinuation of lithium carries a high risk of **rebound mania** and should be avoided in patients with long-term stability.- **Lamotrigine** is primarily used for **bipolar depression prophylaxis** and is not the first-choice replacement for preventing mania in Type I bipolar disorder.
Question 95: A 47-year-old woman with a 15-year history of paranoid schizophrenia presents to the community mental health team. She has been stable on risperidone long-acting injection 50mg fortnightly for the past 3 years. She reports new onset amenorrhoea for 6 months and occasional milky discharge from her nipples. Blood tests show prolactin level of 2800 mU/L (normal range 102-496 mU/L). She is otherwise well and wishes to continue her current treatment as she feels it controls her symptoms effectively. What is the most appropriate management?
A. Switch to aripiprazole long-acting injection (Correct Answer)
B. Add cabergoline to current regimen
C. Reduce risperidone dose to 37.5mg fortnightly
D. Switch to olanzapine oral therapy
E. Continue current treatment and monitor prolactin levels
Explanation: ***Switch to aripiprazole long-acting injection***- **Aripiprazole** is a **dopamine partial agonist** that effectively reduces **prolactin** levels while maintaining adequate therapeutic efficacy for schizophrenia.- Switching to the **long-acting injection** (LAI) formulation ensures continued **adherence** and stability in her psychiatric treatment, while resolving the symptomatic **hyperprolactinaemia** (amenorrhoea and galactorrhoea).*Add cabergoline to current regimen*- **Cabergoline** is a potent **dopamine agonist** that would counteract the antipsychotic effect of risperidone, significantly risking **psychotic relapse**.- Adding another medication increases **polypharmacy**, the risk of drug-drug interactions, and potential for adverse effects, which should be avoided if a monotherapy alternative exists.*Reduce risperidone dose to 37.5mg fortnightly*- While **risperidone-induced hyperprolactinaemia** is dose-dependent, a small reduction may not sufficiently lower the severely elevated prolactin level (2800 mU/L) to resolve symptoms.- Lowering the dose of an effective, stable maintenance treatment carries a high risk of **psychotic relapse** in a patient who has been well-controlled for three years.*Switch to olanzapine oral therapy*- Moving from a long-acting injection to **oral therapy** in a patient with chronic paranoid schizophrenia significantly increases the risk of **non-adherence**, which is a primary reason for relapse.- Although **olanzapine** has a lower propensity for hyperprolactinaemia compared to risperidone, it is not as effective at reducing existing elevated prolactin as aripiprazole, and the adherence risk is paramount.*Continue current treatment and monitor prolactin levels*- Simply monitoring is an inappropriate management strategy given the patient is **symptomatic** (amenorrhoea and galactorrhoea), indicating a significant clinical problem.- Long-term untreated hyperprolactinaemia leads to **hypoestrogenism**, increasing the risk of serious complications like **osteoporosis**, bone fractures, and potential cardiovascular issues, necessitating intervention.
Question 96: A 52-year-old woman with a 25-year history of bipolar affective disorder has been stable on lithium carbonate 1000mg daily for 15 years. She presents for routine monitoring. Blood tests show: lithium level 0.75 mmol/L, sodium 138 mmol/L, potassium 4.0 mmol/L, urea 8.2 mmol/L, creatinine 125 μmol/L, eGFR 52 ml/min/1.73m², calcium 2.65 mmol/L (normal 2.20-2.60), PTH 8.5 pmol/L (normal 1.6-6.9), TSH 2.8 mU/L, free T4 14 pmol/L. She is clinically euthymic with no symptoms. Previous eGFR 1 year ago was 68 ml/min/1.73m². What is the most appropriate next step in management?
A. Continue lithium and refer for parathyroid imaging
B. Stop lithium immediately due to declining renal function
C. Switch lithium to sodium valproate due to hypercalcaemia
D. Reduce lithium dose to 800mg daily and recheck renal function in 1 month
E. Continue lithium, monitor renal function monthly, and refer to endocrinology for hyperparathyroidism (Correct Answer)
Explanation: ***Continue lithium, monitor renal function monthly, and refer to endocrinology for hyperparathyroidism***
- The elevated **calcium (2.65 mmol/L)** and inappropriately high **PTH (8.5 pmol/L)** are characteristic of **lithium-induced primary hyperparathyroidism**, necessitating an endocrinology referral.
- Despite the decline in **eGFR (52 ml/min/1.73m²)**, abrupt cessation of lithium in a stable patient risks relapse; therefore, continuation with **monthly renal function monitoring** is the most appropriate balance.
*Continue lithium and refer for parathyroid imaging*
- While parathyroid involvement is central, referral to **endocrinology** for a comprehensive assessment is the initial step before determining the need for and type of parathyroid imaging.
- This option overlooks the critical need for increased **renal function monitoring** given the documented decline in eGFR.
*Stop lithium immediately due to declining renal function*
- **Immediate discontinuation** of lithium after 15 years of stability carries a very high risk of **bipolar relapse**, which could be clinically devastating for the patient.
- The current **eGFR (52 ml/min/1.73m²)**, though reduced, is not typically an absolute indication for immediate cessation, but rather for closer monitoring and specialist review.
*Switch lithium to sodium valproate due to hypercalcaemia*
- **Hypercalcaemia** is a manifestation of the underlying hyperparathyroidism, which requires direct management by an **endocrinologist**, not an immediate switch to a different mood stabilizer.
- Switching from a long-established and effective treatment like lithium risks **destabilizing the patient's mood** and does not directly treat the hyperparathyroidism.
*Reduce lithium dose to 800mg daily and recheck renal function in 1 month*
- The patient's **lithium level (0.75 mmol/L)** is currently within the therapeutic range, and dose reduction could lead to a loss of **mood stability**.
- A simple dose reduction does not address the underlying **hyperparathyroidism** or provide a comprehensive plan for managing the progressive renal decline.
Question 97: A 26-year-old woman presents with her first episode of psychosis. She describes a 2-month history of hearing her thoughts spoken aloud, believing that her colleagues can hear her thoughts, and experiencing her actions being controlled by an external force. She has social withdrawal and neglect of self-care. Mental state examination confirms thought echo, thought broadcasting, and passivity phenomena. There is no substance use, and medical investigations are normal. Considering the prognostic factors in first-episode psychosis, which feature in her presentation is associated with the poorest long-term outcome?
A. Young age of onset at 26 years
B. Presence of Schneiderian first-rank symptoms
C. Insidious onset over 2 months (Correct Answer)
D. Female gender
E. Absence of prominent affective symptoms
Explanation: ***Insidious onset over 2 months***- An **insidious onset** (gradual development) of psychotic symptoms is a well-established predictor of a **poorer long-term prognosis** and higher risk of chronic disability compared to an acute onset.- This pattern often reflects a more severe underlying neurobiological process and is linked to **greater functional decline** and a lower likelihood of returning to baseline functioning.*Presence of Schneiderian first-rank symptoms*- While **thought echo**, **broadcasting**, and **passivity phenomena** are classically used to diagnose schizophrenia, they do not correlate with the severity of the long-term **prognostic outcome**.- Studies show that these specific positive symptoms respond similarly to antipsychotics and do not necessarily predict future **relapse rates** or social functioning.*Female gender*- **Female gender** is actually considered a **good prognostic factor** in psychotic disorders.- Women typically have a **later age of onset**, better premorbid adjustment, and a more favorable response to treatment compared to men.*Young age of onset at 26 years*- While a very young onset (e.g., childhood or early adolescence) is a poor prognostic sign, an onset at **26 years** is relatively standard for females and is not as significant a negative predictor as an **insidious onset**.- Generally, the **older the age of onset**, the better the prognosis, as the individual has had more time for social and occupational development.*Absence of prominent affective symptoms*- The lack of mood symptoms (like depression or mania) makes a diagnosis of **schizoaffective disorder** less likely and shifts the profile toward schizophrenia, which generally has a worse prognosis than mood-related psychosis.- However, on its own, it is considered less of a negative prognostic indicator than the **gradual, insidious development** of the primary psychotic symptoms.
Question 98: A 35-year-old man with a 10-year history of bipolar affective disorder type I is reviewed in clinic. He has had five manic episodes and three depressive episodes. He has tried lithium (stopped due to tremor), sodium valproate (stopped due to weight gain), and quetiapine (stopped due to sedation). He is currently on lamotrigine 200mg daily but has had two depressive episodes in the past year requiring admission. His current mood is stable. He consents to trying a new medication. What is the mechanism of action of lamotrigine that makes it particularly effective for bipolar depression?
A. Inhibition of voltage-gated sodium channels reducing glutamate release (Correct Answer)
B. Enhancement of GABA-mediated inhibitory neurotransmission
C. Blockade of dopamine D2 receptors in the mesolimbic pathway
D. Inhibition of serotonin reuptake at the synaptic cleft
E. Antagonism of NMDA glutamate receptors
Explanation: ***Inhibition of voltage-gated sodium channels reducing glutamate release***
- Lamotrigine's clinical efficacy in **bipolar depression** is driven by its ability to stabilize neuronal membranes and prevent the presynaptic release of **excitatory glutamate**.
- This modulation of the **glutamatergic system** is a unique property among mood stabilizers, which typically target mania more effectively than depression.
*Enhancement of GABA-mediated inhibitory neurotransmission*
- This is the primary mechanism for medications like **benzodiazepines** and certain other anticonvulsants such as **valproate**.
- While lamotrigine is an anticonvulsant, it does not significantly increase **GABA levels** or activity.
*Blockade of dopamine D2 receptors in the mesolimbic pathway*
- This mechanism describes the action of **antipsychotic medications** like quetiapine, which the patient previously stopped due to sedation.
- **D2 receptor antagonism** is useful for treating acute mania and psychosis but is not how lamotrigine exerts its antidepressant effects.
*Inhibition of serotonin reuptake at the synaptic cleft*
- This is the mechanism of action for **SSRIs**, which carry a risk of inducing **manic switches** if used as monotherapy in bipolar I disorder.
- Lamotrigine does not have clinically significant effects on the **serotonin transporter (SERT)**.
*Antagonism of NMDA glutamate receptors*
- This mechanism is associated with drugs like **ketamine** or **memantine**, which act post-synaptically on glutamate receptors.
- Lamotrigine acts **pre-synaptically** to reduce glutamate release rather than blocking the **NMDA receptor** itself.
Question 99: A 49-year-old man with treatment-resistant paranoid schizophrenia has been on clozapine 700mg daily for 4 years. He presents with a 2-week history of worsening auditory hallucinations and persecutory delusions despite good previous response. He has been compliant with medication. He is a heavy smoker (30 cigarettes/day) but stopped smoking 3 weeks ago using nicotine patches after developing pneumonia. Clozapine level taken yesterday is 620 ng/mL (therapeutic range 350-600 ng/mL). Which pharmacokinetic interaction best explains his elevated clozapine level?
A. Nicotine patches inhibit cytochrome P450 1A2 enzyme activity
C. Pneumonia causes reduced hepatic metabolism of clozapine
D. Nicotine replacement therapy increases clozapine absorption
E. Inflammation from pneumonia inhibits cytochrome P450 enzymes
Explanation: ***Smoking cessation reduces cytochrome P450 1A2 enzyme induction***- Polycyclic aromatic hydrocarbons in **tobacco smoke** are potent inducers of the **CYP1A2** enzyme, which significantly increases the metabolism and clearance of clozapine.- When a heavy smoker stops smoking, this **enzymatic induction** is lost, leading to decreased clozapine metabolism and a subsequent **increase in plasma levels** (as observed at 620 ng/mL).
*Nicotine patches inhibit cytochrome P450 1A2 enzyme activity*- The **nicotine** itself does not significantly induce or inhibit the **CYP1A2** enzyme; the induction effects are primarily caused by other compounds like **polycyclic aromatic hydrocarbons** in tobacco smoke.- **Nicotine patches** deliver nicotine without these enzyme-inducing chemicals, thus they do not inhibit CYP1A2 activity.
*Pneumonia causes reduced hepatic metabolism of clozapine*- While severe acute illness can sometimes impact drug metabolism, **pneumonia** is not a direct or common mechanism for causing a sustained reduction in hepatic metabolism sufficient to explain this clozapine elevation.- The **cessation of smoking** is a far more potent and well-established factor in altering **CYP1A2** activity and clozapine levels, making it the most likely explanation.
*Nicotine replacement therapy increases clozapine absorption*- **Nicotine replacement therapy (NRT)**, including patches, is used to manage withdrawal symptoms and does not significantly alter the **gastrointestinal absorption** or bioavailability of clozapine.- The interaction between smoking and clozapine is predominantly a **metabolic (pharmacokinetic)** one involving enzyme induction, not altered absorption.
*Inflammation from pneumonia inhibits cytochrome P450 enzymes*- High levels of **inflammatory cytokines** can indeed inhibit some CYP enzymes, but this effect is generally less potent and more transient compared to the well-documented impact of **smoking cessation** on **CYP1A2 induction**.- Given the 3-week timeline coinciding with **smoking cessation** and the known interaction with clozapine, the loss of enzyme induction is a more direct and clinically relevant explanation for the elevated levels than a non-specific inflammatory effect.
Question 100: A 27-year-old woman with a 4-year history of bipolar affective disorder type I presents to the emergency department with confusion, coarse tremor, vomiting, and diarrhoea for 2 days. She has been taking lithium carbonate 1200mg daily. One week ago, her GP prescribed ibuprofen 400mg three times daily for ankle pain following a sports injury. Observations: temperature 37.8°C, pulse 95/min, BP 110/70 mmHg. Blood tests show: sodium 144 mmol/L, potassium 4.8 mmol/L, urea 12.5 mmol/L, creatinine 145 μmol/L, lithium level 1.9 mmol/L. What is the underlying mechanism causing her presentation?
A. NSAIDs enhance lithium transport across the blood-brain barrier
B. NSAIDs reduce renal lithium clearance by inhibiting prostaglandin synthesis (Correct Answer)
C. NSAIDs cause gastric irritation leading to reduced lithium absorption
D. NSAIDs increase lithium absorption in the gastrointestinal tract
E. NSAIDs cause volume depletion through gastrointestinal side effects
Explanation: ***NSAIDs reduce renal lithium clearance by inhibiting prostaglandin synthesis***- **NSAIDs** like ibuprofen inhibit **prostaglandin synthesis** in the kidneys, which normally maintain renal blood flow and function.- This inhibition leads to decreased **Glomerular Filtration Rate (GFR)** and increased **proximal tubule reabsorption** of sodium and lithium, causing the observed toxic lithium level (1.9 mmol/L) and renal impairment (elevated urea and creatinine).*NSAIDs enhance lithium transport across the blood-brain barrier*- While lithium toxicity causes neurological symptoms like **confusion** and **coarse tremor**, this is a result of high systemic lithium levels, not enhanced transport across the **blood-brain barrier** by NSAIDs.- The primary drug interaction mechanism between **ibuprofen** and **lithium** involves renal excretion, not direct central nervous system transport.*NSAIDs cause gastric irritation leading to reduced lithium absorption*- **Gastric irritation** by NSAIDs would typically lead to **reduced drug absorption** and lower therapeutic levels, which is contrary to the presentation of **lithium toxicity**.- The gastrointestinal symptoms (vomiting and diarrhoea) in this patient are manifestations of **lithium toxicity** itself, rather than a cause of altered absorption.*NSAIDs increase lithium absorption in the gastrointestinal tract*- There is no established pharmacological mechanism by which **NSAIDs** increase the rate or extent of **lithium absorption** from the gastrointestinal tract.- **Lithium** is already almost completely absorbed orally; the problem in toxicity is usually related to its **elimination**.*NSAIDs cause volume depletion through gastrointestinal side effects*- While **volume depletion** (which can be exacerbated by gastrointestinal symptoms) can worsen lithium toxicity by increasing reabsorption, the **primary and direct mechanism** of NSAID-induced toxicity is their effect on **renal prostaglandin synthesis**.- The patient's elevated **urea** and **creatinine** directly indicate impaired renal function, which is a consequence of the NSAID's direct effect on kidney physiology, leading to reduced **lithium clearance**.
