Simply Psych EDU's
Drug-Drug Interactions
Important Drug-Drug Interactions
Valproic acid (VPA) + Lamotrigine:
Valproic acid (VPA) increases lamotrigine levels
Increases risk of Steven-Johnson’s Syndrome (SJS/TEN)
When using both, decrease the dose of lamotrigine by 50%
Carbamazepine (CBZ) is an inducer of CYP3A4:
CBZ induces its own metabolism
CBZ induces the metabolism of numerous other medications including oral contraceptives, clozapine, alprazolam, buspirone, and clonazepam
Lithium + NSAIDs (not aspirin), ACE Inhibitors, Thiazide diuretics, low sodium diet:
Increases lithium levels
Lithium + caffeine, theophylline, high sodium diet:
Decreases lithium levels
Grapefruit Juice
Grapefruit juice is a potent inhibitor of CYP3A4 and P-glycoprotein
Grapefruit juice increases blood levels of many medications metabolized by CYP3A4
Smoking Tobacco cigarettes:
Induces activity of CYP1A2
The induction does not appear to be from the nicotine, but from the hydrocarbons in smoke
Decreases blood levels of medications metabolized by CYP1A2 (Olanzapine, Clozapine, Caffeine)
Tyramine:
Increased risk of hypertensive crisis when eating tyramine containing foods while taking MAOIs, SSRIs, TCAs, Pseudoephedrine, and Stimulants
Tyramine-rich foods include banana peel, beer, fava beans, aged cheese, sauerkraut, sausage, soy sauce, concentrated yeast extract.
Fluoxetine, Paroxetine, and Bupropion are potent inhibitors of CYP2D6:
They can raise blood levels of medications metabolized by CYP2D6.
Tamoxifen and Codeine are prodrugs requiring metabolism by CYP2D6. Efficacy of these drugs may be decreased when used with inhibitors of CYP2D6.
Antimicrobial-Psychotropic Drug Interactions:
Antimalarials: Increase phenothiazine (e.g. chlorpromazine) levels
Azoles: Increase alprazolam, midazolam, and buspirone levels
Clarithromycin, Erythromycin: Increase alprazolam, midazolam, carbamazepine, clozapine, and buspirone levels
Quinolones: Increase clozapine and benzodiazepine levels but decreases benzodiazepine effects
Isoniazid: Increases haloperidol and carbamazepine levels. Isoniazid + disulfiram can cause ataxia
Linezolid: Serotonin syndrome if used with serotonergic drugs
Other Interactions/Adverse Reactions:
Erythromycin, Clarithromycin, and Ketoconazole: QT prolongation and ventricular arrythmias with TCAs and antipsychotics
Linezolid is an irreversible MAO-A inhibitor: Serotonin syndrome and Hypertensive crisis
Isoniazid is a weaker MAO inhibitor: Reports of Serotonin syndrome and hypertensive crisis
DRUG INTERACTION TABLES
Nucleoside Reverse Transcriptase Inhibitors (NRTIs) | Neuropsychiatric Side Effects |
Abacavir | Depression, Mania, Suicidal ideation, Anxiety |
Psychosis, Insomnia, Nightmares, Fatigue | |
Didanosine | Nervousness, Agitation, Mania, Lethargy |
Emtricitabine | Depression, Odd dreams, Insomnia, Confusion, Irritability |
Interferon-a-2a | Depression, Suicidal ideation, anxiety, mania, psychosis, insomnia, delirium, altered cognition |
Lamivudine | Depression, Insomnia, Dizziness, dystonia |
Zidovudine | Anxiety, Agitation, Restlessness, Insomnia, Mania, Psychosis |
Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) | |
Delavirdine | Anxiety, Agitation, Amnesia, |
Lightheadedness/dizziness | |
Efavirenz | Anxiety, Insomnia, Irritability, Depression |
Suicidal ideation, psychosis, Nightmares, Vivid dreams | |
Lightheadedness/dizziness | |
Nevirapine | Vivid dreams, Nightmares, Visual hallucinations |
Delusions, Mood Instability | |
Lightheadedness/dizziness | |
Etravirine | Insomnia, lightheadedness/dizziness |
Rilpivirine | Odd Dreams, Insomnia, lightheadedness/dizziness |
Protease Inhibitors | |
Atazanavir | Depression, Insomnia |
Fosamprenavir | Depression |
Indinavir | Anxiety, Agitation, Insomnia |
Lopinavir and Ritonavir | Insomnia |
Nelfinavir | Depression, Anxiety, Insomnia |
Ritonavir | Anxiety, Agitation, Euphoria |
Hallucinations, Taste changes | |
Decreased libido | |
Saquinavir | Anxiety, Agitation, Euphoria |
Depression, Hallucinations | |
Excessive dreaming | |
Tipranavir | Depression |
Integrase Inhibitors | |
Raltegravir | Depression, suicidal ideation, psychosis |
Vivid dreams, nightmares, vertigo, | |
Lightheadedness/dizziness | |
Elvitegravir | Depression, Insomnia, Suicidal ideation |
Dolutegravir | Insomnia, Fatigue |
Fusion Inhibitors | |
Enfuvirtide | Depression, Insomnia |
Lithium Toxicity
Lithium Toxicity | Causes | Presentation | Treatment |
---|---|---|---|
Overdose | Nausea | Hold/Discontinue Lithium | |
Dehydration | Vomiting | Monitor lithium levels every 2-4 hours | |
Hyponatremia (low sodium) | Diarrhea | Intravenous (IV) Fluids | |
Low GFR (Glomerular Filtration Rate) | Ataxia | Hemodialysis recommended if Lithium level >2.5 mEq/L with signs of neurotoxicity | |
Renal Impairment/Failure/Disease | Confusion | Hemodialysis recommended if no improvement with IV fluids | |
Drug Interactions | Tremor | Hemodialysis recommended if Lithium level >4.0 mEq/L | |
Diuretics (except loop diuretics) | Slurred Speech | ||
NSAIDs (except aspirin) | Seizures | ||
ACE Inhibitors | Abnormal Movements |
Lithium Level Monitoring
Lithium Monitoring | Target Lithium Level | Recommended Labs |
---|---|---|
Acute Mania | 0.8-1.2mEq/L | Baseline: CBC, CMP, Cr, BUN, TSH, Weight, EKG (in pts>50yo or with cardiac disease) |
Maintenance | 0.6-1.0 mEq/L | After 1 week, 1 month, 6 months, and 12 months of starting lithium: Lithium Level, TSH, BUN/Cr, Electrolytes, monitor weight |
Every 6-12 months: Lithium Level, TSH, BUN/Cr, Electrolytes, monitor weight | ||
NOTE: Check Lithium levels after 4-5 half lives (blood should be collected prior to next dose); Also check lithium levels after dosage changes, addition of other drugs, or if suspecting toxicity |