Transcript Medicines and drugs

Medicines and drugs
•D2: Antacids
•D8: Drug Action
D2: Antacids
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D.2.1: State and explain how excess acidity in the stomach can be reduced by the
use of different bases
Gastric acid is an acid that is found in the stomach and consists highly of HCl and a
pH value of 2.
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An Antacid is any substance, generally a base or basic salt, which counteracts
stomach’s acidity. Antacids are stomach acid neutralizers. They are weak bases
such as metal oxides, hydroxides, carbonates, and hydrocarbonates.
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Antacids perform a neutralization reaction. They buffer gastric acid, raising the pH
to reduce acidity in the stomach
D2: Antacids
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Dyspepsia is a condition where it is hard or difficult for the person to
digest food. This is due to excess acid, and can be fought by taking
antacids.
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Examples of antacids and typical neutralization reactions:
NaCHO3(s) + HCl(aq) -----► H2O(l) + NaCl(aq) + CO2(g)
MgO(s) + 2HCl(aq) -----► MgCl2(aq) + H2O(l)
Mg(OH)2 + 2HCl(aq) -----► MgCl2(aq) + 2H2O(l)
Al(OH)3(s) + 3HCl(aq) -----► AlCl3(aq) + 3H2O(l)
Antacids
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bad effects from antacids include:
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Carbonates: A chemical reaction between the carbonate and hydrochloric acid
may produce carbon dioxide gas. This causes gastric distension which may not be
well tolerated. Carbon dioxide formation can also lead to headaches and
decreased muscle flexibility.
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Aluminum hydroxides: aluminium hydroxide may lead to the formation of insoluble
aluminium phosphate complexes, with a risk for decrease the level of phosphate
in the blood. It can also soften the person's bones.
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Sodium hydro carbonates: intake of sodium hydro carbonates may cause heart
failure.
Drug action
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D.8.1: describe the Importance of geometrical isomerism in drug action
When a drug molecule contains a carbon to carbon double bond, or a ring where
there is restricted rotation, then it may have geometric isomerism. The two
different geometric isomers may have very biological different effects. For
example, diamminedichloroplatinium (II). This compound has a formula of
Pt(NH3)2Cl2 has a cis- and a trans- isomer.
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The cis- isomer is highly effective in the treatment of testicular and ovarian
cancers, as well as other forms of cancer. Trans- platin is not an effective anticancer drug.
D.8.2: Discuss the importance of
chirality in drug action
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Drug molecules that process a chiral carbon atom will exist in two different
enantiomeric forms. For example thalidomide.
sickness in
deformities in the
thalidomide alleviates the symptoms of morning
pregnant woman; the other causes severe
limbs of the baby.
D.8.3: Explain the importance of the
beta-lactam ring action of penicillin
• All penicillins contain a 4-membered beta-lactam ring. The ring contains 2
carbon atoms that are sp3 hybridized, a nitrogen atom that is sp3
hybridized, and a carbon atom that is sp2 hybridized. This is similar to the
combination of two amino acids cysteine and valine.
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Penicillin
Cysteine
Valine
• Because of the restrictions of the ring, the normal bond angles of 109.5
and 120 are not able to be obtained, and so the ring becomes strained.
This makes the amide highly reactive. The ring opens so that the penicillin
can become covalently bonded to the enzyme that synthesizes the cell
walls of the bacterium, thus blocking its action.
D.8.4: explain the increased potency of
diamorphine (heroin) compared to morphine
• Heroin is stronger than morphine. This can be explained due to the
difference in polarity of the two substances.
• Morphine molecules contain two polar hydroxyl groups; in heroin, these
molecules are replaced by ethanoate groups.
• These two ester groups make it much less polar than morphine and more
soluble in lipids, which are non-polar.
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Polar
groups
Morphine
Heroin
Much
less
Polar
groups