PP+401+-+9

=Patient developing lithium toxicity after addition of enalapril=

//Kara Jones (53 years old) has been coming to your pharmacy since earlier this year. You// //have had several chats with her and she has always been very pleasant. You know that she// //lives with and takes care of her elderly mother. Kara’s dispensing history so far at your// //pharmacy is as follows:

//

Problem
Trimethoprim causing increased hyperkalaemia (effects in renal impairment - could still interact with enalapril?) Patient may have taken Ural during UTI, which contains sodium bicarbonate, rendering lithium as less effective Introduction of enalapril on renal function (if renal impairment, ACEi can further impair renal function) - causing decreased elimination of lithium, hence lithium toxicity

This scenario will depend on the presentation of the patient: - lithium toxicity: mild - apathy, lethargy, muscle weakness accompanied by nausea and irritability moderate - coarse tremor, slurred speech, unsteady gait, drowsiness, confusion, muscle twitches, blurred vision severe - seizures, stupor, coma, cardiovascular collapse - sub-therapeutic doses of lithium: insufficient control of bipolar disorder

= =

Questions to Ask
What symptoms are you having? How long have they been going on? When did you last have a lithium level taken? Have there been any changes to medications (or lifestyle) in the past few months?

What to do
- Cease enalapril (skip the next dose) and suggest they see the doctor to check lithium levels - Give paracetamol for their headache and recommend that they keep their fluids up to counteract fluid loss from the diarrhoea The general treatment guidelines for lithium toxicity are as follows: - withdrawal of lithium - saline infusion for serum lithium concentrations less than 3mmol/L; sufficient volume to produce an adequate diuresis is required - this is usually at least 3 litres per day - renal dialysis if patients are either comatose, in shock, severely dehydrated or have serum concentrations of 3mmol/L or more

Be alert for signs and symptoms of lithium toxicity (eg extreme thirst and frequent urination, nausea and vomiting), especially during illness, excessive sweating or low fluid intake; if these occur, stop taking the tablets and seek medical attention immediately. Take blood for lithium concentration at least 8–12 hours after last dose. Measure concentration 5–7 days after starting treatment and after each dose change until stabilised, then every 3 months. Steady state may not be reached for 4–7 days (longer in the elderly or those with renal impairment). Monitor lithium concentration more frequently during illness (eg gastroenteritis), manic or depressive phases, changes in diet or temperature, pregnancy and concomitant medication (eg diuretics).

//Acute mania//, 0.5–1.2 mmol/L. //Prophylaxis//, 0.4–1 mmol/L.

Questions asked by the patient
- **Can I have Nurofen Plus for my headache?** This would not be suitable, as this can interact with both the lithium and enalapril (along with diarrhoea - triple whammy) to cause lithium levels to increase in the body. Paracetamol would be a suitable alternative. - **Can I have an anti-diarrhoeal?** Would be ok as this would reduce further fluid loss, but this along with the paracetamol should not stop the patient from seeing the doctor immediately to check lithium levels (they may not consider going anymore if their symptoms have subsided, even though the cause has not been taken care of). Oral rehydration solutions could be provided to help rehydrate the body and reduce lithium levels.

Resources
scenario- patient asked for nurofen plus questions -is the nurofen plus for you? -what pain are you treating with the nurofen plus -describe onset, frequency and s/s of pain -other s/s, medications, allergies and illnesses? -when did you start enalapril

she tells you -nurofen is for herself -she is using it for headache -she also has diarrhoea -started enalapril 3 weeks ago -will go to doctors in 7 days time

couselling points - explain her headache and diarrhoea MAY be due to higher levels of lithium because of an interaction between lithium and enalapril -she must see the doctor ASAP to revise her drugs-eg tomorrow, as toxic lithium levels may lead to serious effects (you may want to make appointment for her, or at the very least inform the doctor of your suspicion) -warn about severe s/s of lithium toxicity (hyperplexia, seizure, coma, blurred cision, jerks, psychosis, disorientation) - meanwhile cease enalapril (not lithium as she has been stablized on lithium for some time, possible serious effects with sudden withdrawal, enalapril is only 5 mg and recently started therefore unlikely to have major effect, and stopping it will allow us to see if it was indeed the cause) -offer follow up -meanwhile for pain - do not take nurofen (further impair renal and increase lithium toxicity), try panadol -may consider offering something for her diarrhoea