Pharmacokinetics profile of Tablet Lithium
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lithium carbonate prescribing information pharmacokinetics absorption distribution metabolism excretion half life
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Pharmacokinetic profile of oral lithium carbonate tablets
| Parameter | Profile |
|---|---|
| Absorption | Absorbed almost completely from the upper gastrointestinal tract. |
| Time to peak serum concentration (Tmax) | Immediate-release tablet: about 0.25-3 hours. Sustained/controlled-release tablet: about 2-6 hours. |
| Bioavailability | Essentially complete with usual therapeutic oral doses. |
| Distribution | Distributes mainly in total body water. It enters cells slowly and may be sequestered in bone. |
| Volume of distribution (Vd) | Initially about 0.5 L/kg, increasing after equilibration to approximately 0.7-1.0 L/kg. |
| Plasma-protein binding | Negligible or none. |
| Placental and milk transfer | Crosses the placenta and is excreted into breast milk. |
| Metabolism | None. Lithium is an inorganic monovalent cation and is not hepatically metabolized. |
| Elimination | Almost entirely by the kidneys, largely as unchanged lithium in urine. Fecal excretion is insignificant. |
| Renal handling | Freely filtered at the glomerulus; approximately 80% is reabsorbed, predominantly in the proximal tubule, in parallel with sodium handling. |
| Elimination half-life | Commonly 18-36 hours in adults. A longer terminal phase, about 48-72 hours, reflects slow release from intracellular stores. |
| Steady state | Usually reached after about 5 days, though this can be longer with renal impairment or in older adults. |
| Therapeutic drug monitoring | Measure serum lithium as a standardized 12-hour post-dose trough. Timing matters because a non-trough sample is difficult to interpret. |
Lithium concentration rises when renal clearance decreases. Major risk factors are dehydration, sodium depletion, renal impairment, and medicines that reduce renal lithium excretion, particularly thiazide diuretics, NSAIDs, ACE inhibitors, and ARBs.
For a current regulatory source, the DailyMed lithium label reports negligible protein binding, Vd 0.7-1 L/kg after equilibration, renal excretion with about 80% proximal tubular reabsorption, and a half-life of about 18-36 hours. Textbook values: Katzung's Basic and Clinical Pharmacology, 16th Edition, p. 822; Tietz Textbook of Laboratory Medicine, 7th Edition, p. 2019-2022.
Clinical note: because lithium has a narrow therapeutic index, do not adjust doses solely from one level without confirming the sample timing, renal function, hydration status, sodium balance, concurrent medicines, and clinical symptoms.
what are the drugs which it gets interacted
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site:dailymed.nlm.nih.gov lithium carbonate drug interactions diuretics NSAIDs ACE inhibitors ARBs metronidazole
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https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?set…
Lithium has important interactions because it is cleared almost entirely by the kidneys.
Drugs that can increase lithium levels and toxicity risk
These often require avoiding the combination when possible, or checking lithium and renal function soon after starting or changing the drug.
| Drug/class | Examples | Main concern |
|---|---|---|
| Thiazide diuretics | Hydrochlorothiazide, chlorthalidone, indapamide | High-risk increase in lithium level due to sodium loss and increased renal lithium reabsorption |
| Other diuretics | Furosemide, torsemide, spironolactone | Can increase levels, especially with dehydration, older age, or renal disease |
| NSAID painkillers | Ibuprofen, naproxen, diclofenac, indomethacin, celecoxib | Reduce renal blood flow and lithium excretion. Aspirin is generally less problematic, but should still be discussed with the prescriber |
| ACE inhibitors | Enalapril, lisinopril, ramipril | May substantially increase lithium, sometimes after several days to weeks |
| ARBs | Losartan, valsartan, telmisartan, candesartan | Same concern as ACE inhibitors |
| Metronidazole | Metronidazole | Can reduce lithium clearance and raise its serum concentration |
The official lithium prescribing information specifically lists diuretics, NSAIDs, renin-angiotensin system antagonists such as ACE inhibitors/ARBs, and metronidazole as drugs that may raise lithium concentrations.
Drugs that can increase neurologic or other adverse effects
These may not always raise the lithium concentration, but the combination can increase toxicity symptoms.
- Antipsychotics: haloperidol, chlorpromazine, risperidone, olanzapine, quetiapine, clozapine. Rarely, severe neurotoxicity, extrapyramidal symptoms, encephalopathy, or neuroleptic malignant syndrome can occur.
- Serotonergic antidepressants: SSRIs such as sertraline, fluoxetine, escitalopram; SNRIs such as venlafaxine and duloxetine; and drugs such as tramadol, linezolid, triptans, and St John's wort. These can increase the risk of serotonin syndrome.
- Carbamazepine: may increase dizziness, ataxia, tremor, confusion, and other neurotoxic effects. Its potential to cause hyponatremia can also promote lithium retention.
- Calcium-channel blockers: verapamil and diltiazem have occasionally been associated with neurotoxicity when combined with lithium.
- Neuromuscular-blocking drugs used during anesthesia: lithium can prolong their muscle-relaxant effect. Inform the anesthetist and surgeon that you take lithium.
Drugs/substances that may lower lithium levels
- Caffeine and theophylline can increase lithium excretion. Suddenly reducing a high caffeine intake can therefore cause lithium levels to rise.
- Acetazolamide may increase lithium elimination.
- Sodium bicarbonate, high sodium intake, and some osmotic agents may lower levels.
Important non-drug interactions
Lithium concentration can rise with:
- Dehydration from vomiting, diarrhea, fever, heavy sweating, or poor fluid intake
- Low salt intake, crash dieting, or sudden sodium restriction
- Acute kidney injury or worsening chronic kidney disease
Seek urgent medical advice for worsening tremor, unsteady walking, slurred speech, confusion, marked drowsiness, persistent vomiting/diarrhea, or new muscle jerks. These can indicate lithium toxicity.
Do not start, stop, or self-treat with an NSAID or diuretic while taking lithium without contacting the clinician who monitors your lithium. Serum lithium is usually rechecked after an interacting medicine is started, stopped, or dose-adjusted.
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