Non-Essential Ions in Medicine

Study Notes

Non-Essential Ions

Fluoride:
- Used for anticariogenic action (inhibition of dental cavity development)
- Also required for bones and acts as an inhibitor of certain enzymes
- About 95% of orally taken fluoride is absorbed
- Reports indicate that fluoride reduces the prevalence of osteoporosis
- Fluoride facilitates calcium deposition in hard tissues rather than soft tissues, leading to higher visible aortic calcification in low fluoride areas
Bromide:
- Introduced into medicine in 1853 for its antiepileptic effect
- Small doses (0.5-2 gm) cause CNS depression (e.g., KBr)
- Large doses (4-8 gm) depress all reflexes and cause narcotic-like effects
- Bromide's usefulness in epilepsy depends on its ability to depress motor areas of the brain, achievable with large doses
- Currently, bromide (as sodium or potassium salt) is used only for grand mal seizures in children when other drugs are unsuitable
- Rapidly absorbed and excreted in urine
- Repeated doses can accumulate, replacing chloride ions
- Bromism (bromide poisoning) can occur
  - Early signs include insomnia, dizziness, weakness, and headache
- Bromism is treated with sodium chloride (6 gm daily in divided doses) or ammonium chloride, especially when sodium intake is limited.
- Lithium:
  - Readily absorbed from the intestine and accumulates in the body
  - Accumulation depends on sodium intake: low sodium intake accelerates lithium accumulation and potentiates toxicity
  - Lithium intoxication is treated by withholding lithium and providing sodium intake
  - Depresses the CNS and has a diuretic action
  - Lithium carbonate is administered orally for manic depressive disorder
  - Lithium carbonate can affect thyroid function, causing myxedema (deficient thyroid function) and decreasing protein-bound iodine levels
  - Lithium can cause diabetes insipidus (increased urination without glucosuria)
Gold:
- Used in rheumatoid arthritis
- Therapeutic gold compounds are administered intramuscularly (IM)
- Oral administration is poorly absorbed and irritant
- Rapidly enters the plasma where it remains bound to albumin for several days
- Usually administered weekly
- Gold toxicity affects the skin, mucous membranes, joints, blood, kidney, liver, and nervous system
- Toxicity treatment involves stopping administration, supportive treatment, and dimercaprol can be used
Lead:
- Salts were used topically as astringents
- Oral lead is generally absorbed slowly and excreted reasonably well
- Inorganic lead cannot pass through intact skin but is absorbed through abraded skin
- Lead solutions used as astringents can be absorbed systemically
- Organic lead, such as tetraethyl lead, can penetrate skin rapidly
- After absorption, lead is initially found in erythrocytes and soft tissues
- Later, the kidneys contain the most lead, followed by the liver
- Over time, lead redistributes to bone, teeth, and hair
- Lead poisoning manifests by inhibiting heme synthesis
- The most serious lead poisoning symptom is encephalopathy, more common in children
- Renal damage can occur.
- Lead poisoning treatment
  - Chelating agents remove accumulated lead from erythrocytes and soft tissues.
  - Dimercaprol and calcium disodium edetate are used initially, followed by penicillamine for follow-up treatment
  - Acute poisoning from oral ingestion is treated by administering sodium or magnesium sulfate to precipitate lead, followed by gastric lavage
- Once deposited in bone, lead is considered nontoxic until mobilized again
- Even if environmental sources of lead are removed, the possibility of lead poisoning persists due to lead stored in the body
Mercury:
- Metallic mercury is relatively nontoxic
- Mercurous (Hg+) and mercuric (Hg+2) cations are toxic
- Mercury vapor is toxic
- Poisoning by soluble inorganic mercury salts can be avoided
- Organic mercurial compounds are very toxic and are the cause of most reported mercury poisoning
- Toxic effects of mercury are similar to those of lead, due to its combination with protein sulfhydryl groups
- Once absorbed, mercuric cation concentrates mostly in the kidneys, with less concentration in the liver, blood, bone marrow, and other tissues