Alkali metals: Medicinal Inorganic Chemistry 3

Question 1

Describe alkali metals in general?

Answer 1

1. First column in the periodic table
2. S block metals
3. 1 electron in its outer shell- S orbital type
4. Low ionisation energy- M+ (happily form ions)

Question 2

As you go down the periodic table for alkali metals, what happens to the atomic and ionic radius

Answer 2

1. Atomic and ionic radius increase as the outer electrons become further away from the nucleus

2.

Question 3

As you go down the periodic table for alkali metals, what happens to ionisation energy?

Answer 3

1. Ionisation energy will decrease as you go down the group

2. Li+ electrons are closest to the nucleus which means more energy is necessary to separate the two

Question 4

As you go down the periodic table for alkali metals, what happens to electronegativity?

Answer 4

1. Electronegativity (power of an atom to attract electrons towards itself) decreases
2. Electrons are further away from the nucleus
3. More shielding as you go down group 1

Question 5

How do you extract sodium, potassium and lithium from it’s natural source?

Answer 5

1. Electrolysis with two cathodes called “Downs Process”
2. Starting from: NaCl, KCl and LiCl
3. Redox reaction occurs and anode produces chloride gas

Question 6

In the downs process, Na is formed when the cathode produces: Na+ + e- => Na and 2Cl- => Cl2 + 2e- (anode), what is the redox equation and which is oxidation and reduction?

Answer 6

1. Oxidation (loss of electrons at product): 2Cl- => Cl2 + 2e-
2. Reduction (gain of electrons at product): Na+ + e- => Na
3. Redox (combination of both half equations):
   2Cl- + 2Na+ => Cl2 + 2Na

Question 7

How do you store the alkali metals?

Answer 7

Store under oil or oxygen free atmosphere as they’re very reactive

Question 8

How do you form alkali oxides?

Answer 8

Heating the alkali metals in oxygen

Question 9

How do you form alkali chlorides?

Answer 9

1. Reacting metal with Cl2

2. Good aqueous solubility

Question 10

How do you form alkali carbonates?

Answer 10

1. Li2CO3 is sparingly soluble

2. Other good aqueous solubility

Question 11

What are the clinical uses of lithium?

Answer 11

1. Manic depression

2. BIPOLAR DISORDER

Question 12

In terms of lithium, what elements similar relationships and properties to it?

Answer 12

1. Elements close to it in the period (Be and B)
2. Diagonal relationship between lithium and Mg due to similarity in ion size (ionic radius)
3. Li+/Mg2+ salts are similar in solubility

Question 13

Explain how you will use lithium clinically and step by step how to?

Answer 13

1. Taken as oral administration as Li2CO3
2. Dose of 30mmol/day
3. Li2CO3 is least irritating to GI tract
4. Treatment is monitored 12 hours after administration into the blood concentration
5. Very narrow therapeutic index

Question 14

Explain the mechanism of action lithium has?

Answer 14

1. Magnesium in the blood and urine is altered as the lithium displaces it
2. Lithium isn’t soluble in lipids so cannot cross plasma membrane
3. Exchange into cells via:
   - Lithium and sodium counter-transport
   - Anion exchange
   -

Question 15

When lithium is administered into the body, where is it mainly distributed?

Answer 15

1. Bone (a lot)

2. Evenly distributed in Body tissue

Question 16

How does lithium act as a inner mood stabiliser?

Answer 16

1. Inhibition of Inositol monophosphatase: key enzyme in BD (where carbamazepine acts)
2. Lithium can replace magnesium in the enzyme

Question 17

What are the adverse effects that can come from lithium?

Answer 17

1. Narrow therapeutic window makes monitoring blood levels essential during treatment
2. Memory problems
3. Weight gain
4. Polyuria
5. Can CAUSE Diabetes insipidus (large amount of urine and feel thirsty)

Question 18

What are the major drug to drug interactions of lithium and what effects can this produce?

Answer 18

1. NSAIDS: can increase lithium concentration in blood by 60%
2. This can cause reduced lithium clearance through kidneys (lithium poisoning is possible)
3. Diuretics: Sodium depletion makes lithium toxic worse, therefore watch out for repeated use

Question 19

What are the two forms of lithium that are currently available on the market?

Answer 19

1. Lithium Carbonate (CaCO3) (tablets)

2. Lithium Citrate (oral)

Question 20

What is the biological role of sodium?

Answer 20

1. Osmoregulance: regulating water levels in the body: kidney nephrons
   - Na+ electrolyte
2. Helps with the function of the neurones and transmission of nerve impulses (build up of electrostatic potential)
3. Passive transport mechanism: Na+ play role in contraction of smooth muscle
4. Mode of action for several enzymes

Question 21

Define osmosis in relation to sodium?

Answer 21

The physical process of diffusion from an area of low concentration to an area of high concentration across a semi-permeable membrane

Question 22

Define what hypertonic means?

Answer 22

1. The solution has a high concentration of solutes than the surrounding area
2. Area will lose water via osmosis

Question 23

Define what hypotonic means?

Answer 23

1. The solution has a low concentration of solutes than the surrounding area
2. Area will gain water via osmosis

Question 24

Define what isotonic means?

Answer 24

1. The solution has the same concentration of solutes as the surrounding area
2. No water transfer will occur

Question 25

Briefly explain how sodium is transported in active transport?

Answer 25

1. Action potential at cell membrane
2. Na+/K+ pump as active unit
3. 3Na+ for 2K+

Question 26

Describe how sodium is used as a drug?

Answer 26

1. NaCl solution is used intravenously to rehydrate dehydrated people
2. Oral rehydration salts contain NaCl or KCl and citrates
3. Sodium bicarbonate: used to regulate the pH of the urine

Question 27

Describe sodium in terms of diet?

Answer 27

1. Major source of diet as NaCl
2. Hypernatraemia (excess sodium) can result in hypertension
3. Hyponatraemia (less sodium) can result in
   - kidney dysfunction
   - damage to human body via osmotic imbalances
   - Low blood pressure, dehydration, muscle cramps (sodium deficiency)

Question 28

What are the adverse effects of sodium and its toxicity?

Answer 28

1. Toxicity shown when 500 to 1000mg/kg body weight sodium is consumed
2. Symptoms:
   - Vomiting
   - Ulceration of GI tract
   - Renal damage
3. Increased risk of forming kidney stones

Question 29

Describe how potassium works in active transport?

Answer 29

1. Occurs in excitable cells such as neurons, muscle and endocrine cells
2. Na+/K+ active transport is found in the brain and is short lived
3. Na+/K+ ATPase regulates the pump
4. Resting potential is established by this through 3Na+ and 2K+ exchange

Question 30

Describe how the potassium action potential works?

Answer 30

1. Threshold of excitation
2. Na+ channels open (Na+ enters cell)
3. K+ channels open and leave cell
4. No more Na+ enters the cell (peak of curve)
5. Curve drops as K+ continues to leave cell
6. Membrane returns back to return resting potential
   (hyperpolarisation)

Question 31

What is the small therapeutic window for the amount of potassium that should be in the body?

Answer 31

3.5 to 5.0 mmol

Question 32

What are the treatment options for acute hyperkalaemia?

Answer 32

1. Calcium gluconate injections
2. Intravenous injection of soluble insulin
3. Diuretics
4. Dialysis
5. Ion exchange resins
6. Patients with kidney disease have to be carefully monitored

Question 33

What are the treatment options for acute hypokalaemia?

Answer 33

MAIN: Oral supplementation of K+

1. Anti-arrhythmic drugs
2. Renal artery stenosis
3. Severe heart failure drugs
4. Severe K+ losses due to chronic diarrhoea

Question 34

What are the potassium drugs that are available to be used?

Answer 34

1. Form of tablets or liquids in oral application
2. Formulated to allow potassium to be slowly secreted as high concentrations of K+ can be toxic to cells
3. OTC is usually less than 100mg of potassium
4. POTTASIUM CITRATE:
   - OTC for the relief of a mild urinary tract infection (discomfort)