Penicillin - Chem AI

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Questions and Answers

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?

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?

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?

They should be stored in neutral glass containers. Signup and view all the answers

Which bacteria produce penicillinases that deactivate penicillins?

Neisseria gonorrhoeae and Staphylococcus aureus Signup and view all the answers

What is one method used to obtain the compound mentioned?

Starving P.chrysogenum on a medium lacking phenylacetic acid Signup and view all the answers

Which structural modification prevents penicillinase from working effectively?

A side chain that does not fit into the active site Signup and view all the answers

What role does the amidase enzyme play in the described methods?

It cleaves off the side chain of pen.G Signup and view all the answers

Which group of semisynthetic penicillins is specifically designed to resist penicillinase enzymes?

Penicillinase-Resistant Penicillins (PRP) Signup and view all the answers

What is the function of the acid chloride in the final reaction with 6-aminopenicillanic acid?

It reacts with 6-aminopenicillanic acid to form semisynthetic penicillin Signup and view all the answers

What is the significance of phenylacetic acid in the methods described?

It is incorporated into the side chain of penicillin Signup and view all the answers

Which of the following statements about semisynthetic penicillins is true?

They can be categorized into distinct groups based on their spectrum. Signup and view all the answers

Which of the following penicillins is characterized by having polar side chains?

Ampicillin Signup and view all the answers

What is the stability of Nafcillin in acidic conditions compared to Methicillin?

More acid-stable than Methicillin Signup and view all the answers

Which statement about Flucloxacillin is true?

It is similar to Dicloxacillin. Signup and view all the answers

In what form is Nafcillin typically used?

Intravenous and Intramuscular Signup and view all the answers

What form does Ampicillin take in solution at approximately pH 7?

Zwitterionic form Signup and view all the answers

What is required for the ring to effectively interact with the C=O of the side chain?

The two ortho-positions of the ring must be substituted. Signup and view all the answers

Why does methicillin not fit in the active site?

It possesses a bulky side chain due to substitution at the ortho-positions. Signup and view all the answers

How do substituents at o- and p- or m- positions affect the compound's activity?

They increase the likelihood of hydrolysis. Signup and view all the answers

What is the major drawback of methicillin despite its penicillinase-resistance activity?

The methoxy groups make it acid-unstable. Signup and view all the answers

What type of ring structure offers basicity to isoxazoles, allowing oral activity of oxacillin?

An isoxazole ring. Signup and view all the answers

Which of the following statements is true about methicillin?

It is specifically designed to resist penicillinase. Signup and view all the answers

Which chemical feature contributes to the acid instability of methicillin?

Methoxy groups (OCH3). Signup and view all the answers

What route do isoxazole PRPs primarily take for elimination?

Renal and hepatic routes. Signup and view all the answers

What architectural feature is critical for the penicillin's conformational fixity?

A directly attached ring to the C=O group. Signup and view all the answers

Which factor could lead to the loss of activity in a compound similar to methicillin?

Bulky substituents at the ortho-positions. Signup and view all the answers

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.