Podcast
Questions and Answers
What is the effect of an electron-withdrawing group in the side chain of penicillins?
What is the effect of an electron-withdrawing group in the side chain of penicillins?
- It decreases the effectiveness of the drug against bacteria.
- It increases the toxicity of the drug.
- It makes the penicillin more susceptible to penicillinases.
- It enhances acid stability, allowing for oral administration. (correct)
Why is the action of bases considered less significant than that of acids in penicillin reactions?
Why is the action of bases considered less significant than that of acids in penicillin reactions?
- The reaction involving bases has minimal impact under physiological conditions. (correct)
- Bases have a stronger effect on penicillin structure compared to acids.
- Bases are always more reactive than acids in pharmaceutical contexts.
- Bases are ineffective catalysts for penicillin reactions.
What is the role of penicillinases in bacterial resistance?
What is the role of penicillinases in bacterial resistance?
- They stabilize penicillin in acidic environments.
- They act as catalysts for penicillin synthesis.
- They hydrolyze penicillins to inactive compounds. (correct)
- They enhance the acidity of penicillin.
What precaution should be taken when storing pharmaceutical products that contain penicillins?
What precaution should be taken when storing pharmaceutical products that contain penicillins?
Which bacteria produce penicillinases that deactivate penicillins?
Which bacteria produce penicillinases that deactivate penicillins?
What is one method used to obtain the compound mentioned?
What is one method used to obtain the compound mentioned?
Which structural modification prevents penicillinase from working effectively?
Which structural modification prevents penicillinase from working effectively?
What role does the amidase enzyme play in the described methods?
What role does the amidase enzyme play in the described methods?
Which group of semisynthetic penicillins is specifically designed to resist penicillinase enzymes?
Which group of semisynthetic penicillins is specifically designed to resist penicillinase enzymes?
What is the function of the acid chloride in the final reaction with 6-aminopenicillanic acid?
What is the function of the acid chloride in the final reaction with 6-aminopenicillanic acid?
What is the significance of phenylacetic acid in the methods described?
What is the significance of phenylacetic acid in the methods described?
Which of the following statements about semisynthetic penicillins is true?
Which of the following statements about semisynthetic penicillins is true?
Which of the following penicillins is characterized by having polar side chains?
Which of the following penicillins is characterized by having polar side chains?
What is the stability of Nafcillin in acidic conditions compared to Methicillin?
What is the stability of Nafcillin in acidic conditions compared to Methicillin?
Which statement about Flucloxacillin is true?
Which statement about Flucloxacillin is true?
In what form is Nafcillin typically used?
In what form is Nafcillin typically used?
What form does Ampicillin take in solution at approximately pH 7?
What form does Ampicillin take in solution at approximately pH 7?
What is required for the ring to effectively interact with the C=O of the side chain?
What is required for the ring to effectively interact with the C=O of the side chain?
Why does methicillin not fit in the active site?
Why does methicillin not fit in the active site?
How do substituents at o- and p- or m- positions affect the compound's activity?
How do substituents at o- and p- or m- positions affect the compound's activity?
What is the major drawback of methicillin despite its penicillinase-resistance activity?
What is the major drawback of methicillin despite its penicillinase-resistance activity?
What type of ring structure offers basicity to isoxazoles, allowing oral activity of oxacillin?
What type of ring structure offers basicity to isoxazoles, allowing oral activity of oxacillin?
Which of the following statements is true about methicillin?
Which of the following statements is true about methicillin?
Which chemical feature contributes to the acid instability of methicillin?
Which chemical feature contributes to the acid instability of methicillin?
What route do isoxazole PRPs primarily take for elimination?
What route do isoxazole PRPs primarily take for elimination?
What architectural feature is critical for the penicillin's conformational fixity?
What architectural feature is critical for the penicillin's conformational fixity?
Which factor could lead to the loss of activity in a compound similar to methicillin?
Which factor could lead to the loss of activity in a compound similar to methicillin?
Study Notes
Penicillin Structure and Stability
- Electron-withdrawing groups in penicillin side chains produce acid-stable forms that allow for oral administration.
- Bases can catalyze the hydrolysis of penicillin, forming benzylpenicilloic acid, an inactive compound.
- This reaction is less significant than the acid-catalyzed reaction but highlights the importance of storing penicillins in neutral glass containers.
Penicillinase Resistance
- Penicillinases, also known as β-Lactamase, are enzymes that hydrolyze penicillins, generating the inactive penicilloic acid.
- Methicillin and other penicillinase-resistant penicillins achieve resistance by having bulky side chains that do not fit into the active site of penicillinases.
- For a penicillin to be resistant to penicillinases, it must possess an alicyclic or aromatic ring directly connected to the C=O of the side chain, with both ortho-positions on the ring substituted.
Different Types of Penicillin
-
Penicillinase-Resistant Penicillins (PRP): These penicillins are designed to resist degradation by penicillinases.
- Methicillin: Contains methoxy groups that provide maximal penicillinase resistance but is acid-unstable and must be administered intravenously.
- Oxacillin: Oral activity is achieved by the presence of an isoxazole ring, which imparts some basicity to the molecule.
- Dicloxacillin: Similar to oxacillin and not used in the United States.
- Flucloxacillin: Not used in the United States, similar to dicloxacillin.
- Nafcillin: Administered intravenously and intramuscularly as a sodium salt with similar properties to methicillin, but with less acid instability.
-
Broad Spectrum Penicillins: These penicillins possess polar side chains to broaden their spectrum of activity.
- Ampicillin: Amino penicillin G, found as a zwitterion in solutions at pH 7.
- Ticarcillin: Often administered with clavulanate, a penicillinase inhibitor, as Timentin®.
-
Megaspectrum Penicillins: They contain a urea moiety in their side chains and exhibit greater affinity for transpeptidases, resulting in broadened spectrum and higher potency.
- Piperacillin: A common megaspectrum penicillin.
- Mezlocillin and Azlocillin: No longer in use.
Drug Interactions
- Ampicillin and gentamicin can interact with each other, potentially causing inactivation of gentamicin.
- This interaction mainly occurs in vitro and is less likely to occur in patients with normal renal function.
- Patients suffering from renal failure are more susceptible to this interaction due to prolonged drug retention in their bodies
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Description
Test your knowledge on the structure, stability, and resistance of penicillin. This quiz will cover important concepts such as the role of electron-withdrawing groups, penicillinases, and the various types of penicillin. Dive into the chemistry that makes penicillin both effective and challenging to use.
