What are the potential side effects of starting lithium (lithium carbonate) therapy?

Potential Side Effects of Starting Lithium Therapy

Lithium therapy is associated with numerous side effects ranging from mild discomfort to potentially life-threatening toxicity, with the risk increasing significantly as serum lithium levels exceed 1.5 mEq/L. 1

Common Initial Side Effects

• Fine hand tremor, polyuria (excessive urination), and mild thirst often occur during initial therapy and may persist throughout treatment 1
• Transient nausea and general discomfort may appear during the first few days of lithium administration 1
• Gastrointestinal symptoms including pain, discomfort, and diarrhea are common complaints during early treatment 2
• Weight gain of 4-10 kg occurs in approximately 30% of patients on long-term lithium therapy 2

Neurological Effects

• Tremor (4-20% of patients) is the most common neurological side effect, worsened by high caffeine consumption 2
• Cognitive effects including mild impairment of memory, vigilance, reaction time, and tracking have been documented 2
• More serious but rare neurological effects include:
  • Ataxia, choreo-athetotic movements, and hyperactive deep tendon reflexes 1
  • Slurred speech, dizziness, vertigo, and somnolence 1
  • Blackout spells and epileptiform seizures at higher serum levels 1
  • Pseudotumor cerebri (increased intracranial pressure) has been reported and can lead to visual field constriction if undetected 1

Renal Effects

• Reduced urinary concentrating capacity leading to obligate polyuria with secondary thirst 2
• May progress to nephrogenic diabetes insipidus with long-term therapy 2
• Glomerular filtration rate falls slightly in about 20% of patients 2
• Progressive renal insufficiency is a rare but serious complication of long-term lithium therapy 2
• Regular monitoring of renal function is essential, especially in patients with pre-existing renal conditions 3

Endocrine Effects

• Thyroid abnormalities:
  • Inhibition of thyroid hormone release and goiter development 2
  • Increased prevalence of both overt and subclinical hypothyroidism 2
  • Thyrotoxicosis may rarely develop 2
• Hyperparathyroidism and hypercalcemia may occur with long-term treatment 2
• Hypermagnesemia has been reported 2

Cardiovascular Effects

• Cardiac arrhythmia and hypotension may occur 1
• Peripheral circulatory collapse and sinus node dysfunction with severe bradycardia (potentially causing syncope) 1
• ECG changes including reversible flattening, isoelectricity, or inversion of T-waves 1

Dermatological Effects

• Drying and thinning of hair, skin anesthesia, chronic folliculitis 1
• Exacerbation of psoriasis 2
• Alopecia (hair loss) has been reported 1

Risk of Toxicity

• Lithium has a narrow therapeutic range, making therapeutic monitoring essential 4
• Signs of toxicity can occur at serum levels below 1.5 mEq/L in sensitive patients 1
• Early signs of toxicity include diarrhea, vomiting, drowsiness, muscular weakness, and lack of coordination 1
• At higher levels (>2 mEq/L), giddiness, ataxia, blurred vision, tinnitus, and large output of dilute urine may occur 1
• Serum levels above 3 mEq/L can produce complex clinical pictures involving multiple organ systems 1

Monitoring Requirements

• Baseline laboratory assessment before initiating lithium should include:
  • Complete blood cell counts, thyroid function tests, urinalysis 3
  • Blood urea nitrogen, creatinine, and serum calcium levels 3
  • Pregnancy test in female adolescents 3
• Once a stable lithium dose is achieved, lithium levels, renal and thyroid function should be monitored regularly (every 3-6 months) 3
• Serum lithium concentrations should be determined twice per week during the acute phase until stabilized 3
• Target serum concentration is typically 0.6-0.8 mmol/L, though some clinicians prefer 0.8-1.2 mmol/L 4

Special Populations

• Pregnancy: Lithium is rated as category D (positive evidence of risk) and should be avoided during the first trimester unless benefits outweigh risks 2
• Breastfeeding: Safety is controversial as lithium transfers into breast milk, and neonatal kidneys are particularly sensitive to lithium 2
• Elderly patients may require reduced dosing due to decreased lithium clearance with aging 4
• Patients with dysarthria require careful monitoring as lithium may worsen speech disorders 5

Practical Considerations

• Educate patients about early signs of lithium toxicity to facilitate prompt intervention 6
• Sustained-release formulations result in 30-50% reductions in peak plasma concentrations, potentially reducing side effects 4
• Lithium should be discontinued during ECT treatment if clinically possible 6
• Numerous drug interactions can decrease lithium clearance, increasing toxicity risk 4