Thursday, December 13, 2007

Application of chemistry in supplements labelling

Zinc sulphate 66mg
Dose: take one tablet 3 times daily or as directed.

Conversation
Customer: Can u explain what is written on the label? I read from somewhere we should take more than 50mg/day. Here is written 66mg. Three times a day somemore...wont it become toxic to our body?

Answer:
66mg x3=198mg? toxic dose?

USRDA stand for United States Recommended Daily Allowances.
When used orally, zinc is safe in the amounts that do not exceed the tolerable upper intake level of 40-50mg/day. This is because higher dose might decrease copper absorption and result in anemia.

Ask the pharmacist!
This is how we pharmacist calculate

Zinc sulphate= ZnSO4. 7H20
Molecular weight=65+32+16*4+7(2+16)=287

Assume 287mg zinc sulphate contains 65mg of zinc, therefore 1 tablet 66mg of zinc sulphate contains how much zinc?
66*65/287= 14.9mg lor....

14.9mg* 3 is only 44.7mg = NON TOXIC DOSE
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Another common misunderstanding is Calcium.
Is Calcium Lactate 300mg = Calcium Carbonate 300mg?

The calculations is more complicated than it is shown. Pls ask your pharmacist or me if u want to know more.

Calcium Molecular Weight=40
Calcium Carbonate= CaCO3 =100.1
Calcium Citrate= C12H10Ca3O14,4H2O =570.5
Calcium Lactate=C6H10CaO6,xH2O =218.2 (anhydrous); 308.3 (pentahydrate); 272.3(trihydrate)

Questions: (if u think u understand)
1)Are all calcium salts the same?
2)So do u know which calcium contain the most elemental calcium?
3)Is Calcium Lactate 300mg = Calcium Carbonate 300mg?
4) How many calcium carbonate 300mg u have to take/day if the recommended dose is 1200mg/day?
5) Which one is the best calcium?


Answer 1:
No. Usually government hospital supply calcium lactate, retail pharmacy sell more on calcium carbonate and calcium citrate.

Answer 2:
Calcium Carbonate 40/100=40%.
Calcium Citrate 40*3/570.5=21%
Calcium Lactate 40/308.3=13%

Answer 3:
Calcium Lactate 300mg= 13%*300mg = 39mg of elemental calcium
Calcium Carbonate 300mg= 40%*300mg = 120mg of elemental calcium

Answer 4: USRDA: 1000-1200mg/day
1200mg /39= 30 tablets. HAHAHA. Now u should know how many tablet of calcium u should eat if u r getting them from the hospital.

Answer 5: Here, we also need to apply the solubility of Calcium into calculations.

Simplified way:
Calcium carbonate is practically insoluble in water, but dissolve in hydrochloric acid. CaCo3+2HCL= Ca2+,2Cl-, H+, HCO3- (if i am not mistaken, my chemistry a bit karat liao)
This is also why we recommend to take calcium with food as food stimulate acid secretion in the stomach. And do not take antacid or your gastric medicine with your calcium supplements.

Calcium lactate= soluble in water (can take with food or without)
Calcium citrate= slightly soluble in water but freely soluble in diluted hydrochloric acid (can take with food or without)

BEST CALCIUM? I think it would be Calcium Lactate, provided u dont mind swallowing 30 tablets/day. Or else just stick with the 2 tablets of Calcium Carbonate 600mg with food.

For further informations, feel free to ask me. Absorption is a very complicated process.

4 comments:

Ted said...

So do you calculate in front of the customer and show him? lol

ws pang said...

really salute u my friend
we are proud of you.
could u comments on pregnancy calcium requirement HEHE

Anonymous said...

Some correction:
Q
4) How many calcium carbonate 300mg u have to take/day if the recommended dose is 1200mg/day?
A
Answer 4: USRDA: 1000-1200mg/day
1200mg /39= 30 tablets. HAHAHA. Now u should know how many tablet of calcium u should eat if u r getting them from the hospital.

Calcium carbonate=120mg not 39mg

pharmalogik said...

if u dont mind, can u explain how u come up with 120mg and not 39mg? I thought i already show it clearly in my calculations.

pls support your allegations with some prove?

and pls identify yourself also...

regards,
pharmacist who willing to learn from u...hehehe