HRDs- Lithium, Valproate, Carbamazepine, Phenytoin Flashcards
Carbamazepine
RANGE - 4-12mg/L
Indications
Seizure prophylaxis, Trigeminal neuralgia, diabetic neuropathy
MOA: Inhibits neuronal Na+ channels
AEs (HANDBAGS)
H - Hyponatraemia/Hepatic issues
A - Ataxia (co-ordination/speech /balance issues)
N - Nystagmus (rhythm involuntary eye movements)
D - Drowsiness
B - Blurred vision/Blood disorders
A - Arrhythmias
G - GI issues
S - Suicidal thoughts/Skin issues
REDUCED VIA MR Preps
Warnings
Can cause neural tube defects, cardiac/urinary issues & cleft palate. HLA-B*1502 allele increases SJS risk
AVOID in acute porphyria, AV conduction issues, Hx of bone marrow depression
Interactions
Enzyme inducer (CRAP GP’S SHOUT BS)
Carbamazepine is also metabolised by CYP450 Enzymes and auto induces its own metabolism over first 2/3 weeks. Its CONC. and AEs increased by enzyme inhibitor (SICKFACES.COMgf).
AED efficacy reduced by drugs that reduce the seizure threshold (e.g., SSRIs, TCAs, antipsychotics, tramadol).
OTHER
Drug dose increased gradually.
- Signs of severe hypersensitivity: skin rashes, bruising, bleeding, high temp, mouth ulcers (sign of blood toxicity), reduced appetite or abdominal pain (liver toxicity).
- CAN’T drive unless seizure free for 12 months. 6 months after stopping or changing treatment.
- Avoid formulations/brands switching for epilepsy. DON’T stop suddenly. Withdraw gradually (bipolar min 4 weeks).
- In pregnancy use lower side of therapeutic range ensure seizures controlled
- Take VIT D if immobilized for long or not sunny areas.
- Test for HLB allele in east Asians
Phenytoin
RANGE – 10-20mg/L
– Toxicity signs: nystagmus, slurred speech, ataxia, hyperglycaemia, confusion
Indications
Control status epilepticus where benzos fail, reduce seizure freq.
MOA: Reduces neurone excitability = reduced seizures
AEs
P - P45 inducer
H - Hirsutism
E - Enlarged gums
NY - Nystagmus
T - Teratogenicity
O - Osteopenia
I - Interferes with folic acid
N - Neuropathy
Warning
Phenytoin toxicity can cause death (CV collapse, Respiratory depression)
Reduce dose in hepatic impairment
- BLOOD/SKIN disorder - medical advice ASAP (signs as carbamaz)
Interactions
Its a enzyme inducer ((CRAP GP’S SHOUT BS). CONC. increase by enzyme inhibitors.
Other
DON’T STOP Abruptly – gradual withdrawal to stop seizure recurrence.
Seizure driving advice same.
AVOID brand switch
MHRA - Suicidal thoughts risk, risk of death/severe harm from mistake with injectable form.
Contraception needed
Lithium
RANGE – 0.4 - 1 = Maintenance Treatment 0.8 - 1
Indications
Treatment/Prophylaxis - Bipolar (antipsychotics FAIL), mania, recurrent depression, self harming behaviour
AEs Phone pic LITHIUM
Weight gain, QT prolongation, electrolyte imbalance (hypernatremia), hyperglycaemia
- More AEs show in toxicity
Warnings
AVOID in Dehydration, Low Na+ diet, Untreated hypothyroidism, Cardiac disease, Addison’s disease
AVOID abrupt withdrawal.
Interactions
Increase conc. (MAD TN) Metronidazole, ACEi, Diuretics, Tetracyclines, NSAID [Common 1s].
Decrease conc. Na Antacids/ Analgesics, Urinary alkalizing agents (cystitis), Theophylline, Osmotic & Carbonic anhydrase inhibitor diuretics
Increase neurotoxicity risk: Carbamazepine, Antipsychotics, SSRis, Triptans, CCBs [Drugs work on brain mostly].
Increase serotonin syndrome risk: SSRIs, MAOi, Tramadol, St john’s wort, Sumatriptan
Pregnancy/BF – AVOID. IF needed avoid in 1st trimester. Adjust dose in 2nd/3rd – INCREASE. Monitor conc. Closely. If not pregnant use effective contraception.
Other
- Review dose in diarrhoea, elderly, Vomiting, Surgery & intercurrent infection
- Asses need to continue. Maintain PTs after 3/5 yrs on lithium if benefits continue
KEEP SAME BRAND
Hypothyroidism – weight gain, renal issue (polyuria, polydipsia), Benign intracranial HTN (headaches/vision issues), AVOID dietary changes affect sodium levels. GIVE PT LITHIUM treatment pack
Hyponatremia can show lithium toxicity (AVOID dehydration/anything that affects sodium – EXAM Q).
Valproate
Indications
Seizure prophylaxis, Established convulsive status epilepticus where BENZOS FAILED, Bipolar for acute manic Eps, Migraine prevention
MOA: Inhibit sodium channels - reduces neuron excite - reduces seizures
AEs
VALPROATE (acronym)
V- Valproate,
A- Appetite increase (weight gain),
L- Liver failure,
P- Pancreatitis/P450 inhibitor,
R- Reversible hair loss,
O- Oedema,
A- Ataxia (Speech/Balance disorder),
T- Teratogenicity/Tremor,
E- Encephalopathy (brain damage)
Hyponatraemia
Warning
AVOID: women of childbearing potential (esp. around time of conception), 1st trimester, hepatic impairment and REDUCE DOSE in severe renal impairment.
Interactions
Enzymes inhibitor (SICKFACES.COMgf)
Inducer decrease it conc.
Drugs that lower seizure threshold affect efficacy
Other
- SEEK urgent medical attention if feel lethargy, loss of appetite, vomiting or abdo pain (suggest liver toxicity) or bruising, sore mouth or a high temp (both indicate blood abnormalities)
- Seizure driving advice same as
- MHRA: Suicidal thoughts/Behaviour issues. TRY TO AVOID BRAND CHANGE
- NEED PPP for women of childbearing age. Copper IUD (best contraceptive method- EXAM Q). Lamotrigine/Levetiracetam safer in pregnancy
- VIT D supplements if more likely to get VIT D deficient (hijab, Dark skin, indoor ppl. Etc)
- ALWAYS dispense in original packs. Round up or down.
Monitor LFT (and prothrombin time) before and during the first 6 months of treatment.
