HIGH RISK MEDICATION: LITHIUM Flashcards
You are working in a GP surgery. A receptionist asks you to review the blood results of a patient with bipolar disorder.
He currently takes Priadel (lithium carbonate) 800mg od and has been on the same dose for the past 2 years.
Serum lithium concentration0.7 mmol/litre
- Na+139 mmol/l
- K+3.7 mmol/l
- Urea4.6 mmol/l
- Creatinine99 umol/l
You can find no other blood on the system for the past 6 months.
Select the TWO most appropriate actions for this patient
- A.Repeat urea and electrolytes in 2 weeks
- B.Arrange thyroid function tests
- C.Stop lithium and phone psychiatry for advice
- D.Keep patient on the same lithium dose
- E.Increase the lithium dose to 1000mg od
Correct answer: B D
The lithium dose is within range (0.4-1.0 mmol/litre) and does therefore not need to be changed.
No thyroid function tests are given in this scenario and it seems that they have not been performed for at least 6 months. It is therefore important to arrange these.
Lithium salts have a narrow therapeutic index, therefore, serum lithium levels need to be closely monitored. Changes in dietary intake of electrolytes can affect serum lithium levels.
Which of the following electrolytes is most likely to have an adverse effect on serum lithium levels?
Calcium
Magnesium
Phosphate
Potassium
Sodium
The correct answer was Sodium
The sodium-lithium channels can’t differentiate between sodium and lithium, therefore, changes in the diet that reduce or increase sodium intake affect serum lithium levels resulting in sub-therapeutic or toxic levels. Raised calcium levels also need to be monitored but have less impact that sodium. BNF states that patients should not do anything that affects their sodium levels.
A 46-year-old woman was commenced on lithium 400 mg once daily by her GP three months ago for treatment of bipolar disorder. Today she has come in to get a prescription for amoxicillin 500 mg three times a day to treat a dental abscess. She complains of feeling nauseous and has had severe diarrhoea over the last few hours. Upon further questioning, you find that she may have accidentally taken a double dose of her lithium tablets yesterday.
What is the most appropriate advice to give to this patient?
- Sell her loperamide capsules and advise her that she should start feeling better within 24 hours
- She is experiencing a side-effect of lithium, and whilst safe to continue taking it, she may wish to see her GP for an alternative
- She should see her GP as the dose of lithium may need to be reduced
- Stop taking lithium straight away and go to her nearest accident and emergency department as soon as possible
- The symptoms described are not known to be caused by lithium
The symptoms described are signs of lithium toxicity which is likely as the patient may have taken a double dose the day before. Due to the narrow therapeutic range and the severity of potential poisoning the patient requires urgent medical attention and should be referred to her nearest accident and emergency department.
Stop taking lithium straight away and go to her nearest accident and emergency department as soon as possible
You review a 55-year-old man who is known to have bipolar disorder. He has been treated successfully with lithium for the past four years. His lithium level is checked every three months.
Select the two other tests that should be ordered every six months to monitor for adverse effects of lithium therapy.
- A.Full blood count
- B.Urea & electrolytes
- C.Liver function tests
- D.Thyroid function test
- E.Fasting glucose
Correct answer: B D
The tables below show the monitoring requirements of common drugs. It should be noted these are basic guidelines and do not relate to monitoring effectiveness of treatment (e.g. Checking lipids for patients taking a statin)
Cardiovascular drugs:
Statins
- Main monitoring parameters: LFT
- LFTs at baseline, 3 months and 12 months
ACE inhibitors
- Main monitoring parameters: U&E
- U&E prior to treatment
- U&E after increasing dose
- U&E at least annually
Amiodarone
- Main monitoring parameters: TFT, LFT, U&E, CXR prior to treatment
- TFT, LFT every 6 months
Rheumatology drugs
Methotrexate
- Main monitoring parameters: FBC, LFT, U&E
- The Committee on Safety of Medicines recommend ‘FBC and renal and LFTs before starting treatment and repeated weekly until therapy stabilised, thereafter patients should be monitored every 2-3 months’
Azathioprine
- Main monitoring parameters: FBC, LFT
- FBC, LFT before treatment
- FBC weekly for the first 4 weeks
- FBC, LFT every 3 months
Neuropsychiatric drugs
Lithium
- Main monitoring parameters: Lithium level, TFT, U&E
- TFT, U&E prior to treatment
- Lithium levels weekly until stabilised then every 3 months
- TFT, U&E every 6 months
Sodium valproate
- Main monitoring parameters: LFT
- LFT, FBC before treatment
- LFT ‘periodically’ during first 6 months
Endocrine drugs
Glitazones
- Main monitoring parameters: LFT
- LFT before treatment
- LFT ‘regularly’ during treatment
A 45-year-old female with a history of bipolar disorder presents with an acute confusional state. Which one of the following drugs is most likely to precipitate lithium toxicity?
- Sodium valproate
- Atenolol
- Aminophylline
- Sodium bicarbonate
- Bendroflumethiazide
Lithium toxicity can be precipitated by thiazides
Both sodium bicarbonate and aminophylline may reduce plasma concentrations of lithium
You are called to review a 55-year-old lady with a history of bipolar disorder who is being treated with lithium therapy. She appears agitated and confused. The nurse informs you that she has taken a large dose of lithium. Her blood results demonstrate a rapid decline in renal function. You prescribe fluids as part of your initial management.
What is the most appropriate further management?
- Continue IV fluids
- Activated oral charcoal
- Furosemide
- Haemodialysis
- Lactulose
Severe lithium toxicity is an indication for haemodialysis
Important for meLess important
This patient is presenting with what appears to be acute lithium toxicity, which has progressed to renal impairment. There is also evidence of neurological involvement indicating severe toxicity. Initial management would include supportive measures such as fluid resuscitation. Dialysis is indicated in severe lithium toxicity as a method of clearance. Lactulose and activated oral charcoal have no role in the treatment of lithium toxicity.
Management
- mild-moderate toxicity may respond to volume resuscitation with normal saline
- haemodialysis may be needed in severe toxicity
- sodium bicarbonate is sometimes used but there is limited evidence to support this. By increasing the alkalinity of the urine it promotes lithium excretion
A 52-year-old male with bipolar disorder has been stable on lithium therapy for over 10 years. He presents to the emergency department with new onset of diarrhoea, vomiting, muscle twitching and ataxia.
The following blood result has been obtained:
Lithium level 1.6 mmol/l
Which of these medications is most likely to have precipitated this presentation?
- Sertraline
- Omeprazole
- Salbutamol inhaler
- Bendroflumethiazide
- Amoxicillin
Lithium toxicity can be precipitated by thiazides
Important for meLess important
This question describes lithium toxicity, through the clinical features and blood result. Bendroflumethiazide increases the serum concentration of lithium through its effects on renal sodium reabsorption.
Salbutamol may interact to cause torsades de pointes and should be avoided, but would not cause lithium toxicity. Sertraline may interact to cause serotonin syndrome, the presentation of which may be similar to lithium toxicity. However, this is not the correct answer due to the blood result. Omeprazole and amoxicillin do not interact with lithium.
Jackie is a 33-year-old female who is on the psychiatric ward being treated for bipolar disorder. She is currently taking lithium after being started on it 3 weeks ago. The doctor needs to take bloods to check if her levels have stabilised. Her last dose was 9am this morning, it is currently 12pm.
When should the doctor take the bloods?
- Immediately
- In 3 hours
- In 6 hours
- In 9 hours
- In 12 hours
In 9 hours
When checking lithium levels, the sample should be taken 12 hours post-dose
Important for meLess important
The correct answer is 9pm that evening as levels should be checked 12 hours after the last dose which was at 9am this morning.
Ideally, the dose should be taken in the evening so bloods can be taken the following morning.
If taken too soon, the drug will not have had time to be metabolised and excreted so you will likely get a result that is too high which could lead to you decreasing the dose incorrectly.
If taken too late, the drug will have been excreted too much and the patient may have their dose increased incorrectly.
Discuss (4)Improve
You are asked to see a patient on an inpatient psychiatric ward who has been feeling unwell for the last few days. He reports a severe tremor as well as muscle weakness and diarrhoea. His medication chart includes lithium, and you decide to order a lithium level as part of the workup. It comes back at 1.9mEq/l (high). You note that the nursing chart indicates he hasn’t been out of bed much except to smoke and has refused food and drink.
What factor has most likely contributed to this lithium toxicity?
- Dehydration
- Infection
- Cigarette use
- Antibiotic therapy
- Initiation of an antipsychotic
Dehydration is a risk factor for lithium overdose
Important for meLess important
This presentation describes lithium toxicity, caused by too much lithium in the blood. Blood levels are taken frequently for lithium as it has a very narrow therapeutic index (0.6-1.2). Dehydration is a common cause of lithium toxicity especially in patients that are in inpatient care and are not eating or drinking.
1: Correct
2: Infection is unlikely in this presentation but important to rule out
3: Cigarette use is not linked to lithium toxicity
4: Antibiotic use is not linked to lithium toxicity
5: Concurrent anti-psychotic use is unlikely to affect lithium levels
A 56-year-old man presents to the emergency department with seizures.
He has a history of bipolar disorder and migraines.
His medications include lithium, amitriptyline and paracetamol. His partner reports he has recently been using ibuprofen regularly over the counter.
On examination, he is post-ictal and appears dehydrated.
Blood results reveal:
Na+154 mmol/L(135 - 145)
K+5.3 mmol/L(3.5 - 5.0)
Urea12.8 mmol/L(2.0 - 7.0)
Creatinine174 µmol/L(55 - 120)
Lithium+2.6 mmol/L(0.4 - 1.0)
Resuscitation is initiated with intravenous 0.9% normal saline.
What is the definitive management of this presentation?
- Activated charcoal
- Atropine
- Haemodialysis
- N-acetylcysteine
- Sodium bicarbonate
Severe lithium toxicity is an indication for haemodialysis
Important for meLess important
Haemodialysis is indicated in severe lithium toxicity (concentrations in excess of 2 mmol/L) if neurological symptoms or renal failure are present. Given the presentation with seizures and the markedly raised lithium level, haemodialysis would be required. Resuscitation with 0.9% intravenous normal saline alone may be sufficient in mild to moderate lithium poisoning, where the patient is showing non-specific signs of toxicity, such as apathy and restlessness.
Sodium bicarbonate is sometimes used as an adjunct in lithium toxicity for urinary alkalinization but alone it would not be used in this case without the ultimate management step: haemodialysis.
Atropine is an antidote in anticholinesterase poisoning and can treat symptomatic bradycardia, but would not be used in this scenario.
N-acetylcysteine is used to treat paracetamol overdose but has no definitive role in the management of lithium toxicity.
Activated charcoal should not be used in lithium toxicity. Repeated doses given by mouth can however enhance the elimination of some drugs in overdose, for example, carbamazepine and theophylline.
A 40-year-old male calls the GP at 12PM to organise his blood tests after a recent consultation with his psychiatrist. The psychiatrist increased his dose of lithium and requested that the GP organise lithium levels at the correct time post-dose. He took the first increased dose of lithium at 8AM (four hours ago).
In how many hours time does the GP need to organise for his blood to be taken?
- 4 hours
- 6 hours
- 8 hours
- 10 hours
- 12 hours
When checking lithium levels, the sample should be taken 12 hours post-dose
Important for meLess important
The correct answer is 8 hours. Lithium levels should be checked 12 hours post-dose. If the patient took his first increase dose of lithium 4 hours ago, his levels should be checked in 8 hours time to be at 12 hours post-dose.
In 4, 6, 10 or 12 hours would not be the right timings to check lithium levels. Lithium levels should be checked 12-hours post-dose. As he took his first dose 4 hours ago, it should be checked in 8 hours time. 12 - 4 = 8.
A 28-year-old woman is admitted to a psychiatry ward from the emergency department. She was brought by a concerned friend who was worried by her recent behaviour. She had been engaging in large amounts of gambling, spending nearly every night at the local casino and hardly sleeping. When asked if she understands the risks of gambling, she is convinced that nothing can go wrong. She struggles to focus on the topic and begins rambling about investing money in various different businesses that are sure to make her a fortune. A diagnosis of a manic episode is made and she is stabilised on treatment with quetiapine. Subsequently it is decided to initiate lithium to maintain her mood.
When should her serum lithium levels next be monitored?
- 1 week - 12 hours after last dose
- 1 week - 6 hours after last dose
- 3 months - 12 hours after last dose
- 3 months - 6 hours after last dose
- 6 months - 12 hours after last dose
When checking lithium levels, the sample should be taken 12 hours post-dose
Important for meLess important
This patient had an acute manic episode. To prevent her having another manic episode, lithium can be started as a prophylactic mood stabiliser.
Lithium should be monitored weekly when treatment is initiated or dose is changed. The lithium level should be checked 12 hours post-dose. Therefore the lithium levels should next be checked after 1 week, 12 hours after the last dose.
After lithium treatment is established, monitoring frequency can be reduced to 3 monthly. Samples should be taken 12 hours after the last dose.
U&E and TFTs should be monitored every 6 months after initiating treatment.
Angela is a 32-year-old doctor who you referred to the mental health team with suspected bipolar disorder. The psychiatrist has written to you to confirm a diagnosis of bipolar disorder and the commencement of lithium. Her levels have been monitored and she is now stable on treatment, therefore they have requested that you take over the monitoring.
You call Angela and advise that she will need her lithium levels. Angela remembers that it is important that she has these tests at a certain time related to her medication, but cannot remember when.
How would you advise her medication levels to be checked?
- Blood test immediately pre dose every month
- Blood test 6 hours post dose every 3 months
- Blood test 6 hours post dose every month
- Blood test 12 hours post dose every 3 months
- Blood test 12 hours post dose every month
Blood test 12 hours post dose every 3 months
When checking lithium levels, the sample should be taken 12 hours post-dose
A blood test 12 hours post-dose every 3 months is the correct answer.
NICE advises the following with regard to lithium monitoring:
‘Lithium levels are normally measured one week after starting treatment, one week after every dose change, and weekly until the levels are stable. Once levels are stable, levels are usually measured every 3 months. Lithium levels should be measured 12 hours post-dose.’
All the other time intervals are incorrect. A blood test immediately pre-dose is a trough level taken for medications such as twice-daily clozapine.
A 48-year-old woman is reviewed in the clinic. She was recently seen by the psychiatrist and it was recommended that her lithium dose was increased for better symptom control. Her renal function is stable and so you prescribe the increased dose of lithium that is recommended.
When would it be most appropriate to re-check her levels?
- In 1 month
- In 1 week
- In 3 days
- In 3 months
- In 6 months
After a change in dose, lithium levels should be taken a week later and weekly until the levels are stable
Important for meLess important
Lithium monitoring should be performed weekly after initiation and after each dose change until concentrations are stable. In this case, with an increased lithium dose, the levels should be checked again in 1 week. It is usually checked 12 hours after the dose is taken.
One month would be too long to wait after a dose adjustment.
Three days would be too soon to assess lithium levels.
Once lithium levels are stable they can be checked in 3 months’ time, and then every three months for the first year, but they need to be stable before this occurs.
The BNF suggests that if lithium levels remain stable after a year then lithium testing can go to every 6 months in low-risk patients. NICE guidance suggests that 3 monthly testing continues indefinitely. In addition thyroid function tests should be monitored 6 monthly on patients on lithium.
