Review of Pharmacology - 9E (2015)

128. Ans. (b) Trovafloxacin (Goodman & Gilman 11/e p1121)
Fluoroquinolones safe in renal failure are:
• P – Pefloxacin
• M – Moxifloxacin
• T – Trovafloxacin
Chemotherapy A: General Consideration and Non-specific Antimicrobial Agents
129. Ans. (a) Ventricular arrhythmia (Ref: KDT 6/e p692)
• Both sparfloxacin and astemizole blocks cardiac K + channels in high concentration. This property may result in
torsades de pointes (polymorphic ventricular tachycardia).
• Other drugs causing torsades de pointes are:
––
Terfenadine
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Cisapride
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Ziprasidone
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Grepafloxacin
130. Ans. (a) Sulfonamides inhibit bacterial dihydrofolate reductase (Ref: KDT 6/e p685)
• Sulfonamides are antimetabolites that act by inhibiting the enzyme folate synthase. Dihydrofolate reductase is
inhibited by methotrexate, trimethoprim and pyrimethamine.
• These can cause kernicterus in new born if used in late pregnancy.
• At acidic pH, these can get precipitated and result in crystalluria.
131. Ans. (c) A fluoroquinolone is the drug of choice for treatment of an uncomplicated urinary tract infection in a 7 year old
child (Ref: KDT 6/e p689)
• Fluoroquinolones are contra-indicated in children (due to risk of cartilage damage) and pregnant female.
• Most common mode of resistance to fluoroquinolones is mutation in DNA gyrase.
• Dose of fluoroquinolones should be adjusted in renal failure (except moxifloxacin and trovafloxacin).
• These drugs act by inhibiting DNA gyrase.
132. Ans. (d) Skin reactions (Ref: KDT 6/e p684)
Rash is the most common adverse effect seen with the use of sulfonamides.
133. Ans. (b) Ofloxacin (Ref: KDT 6/e p756)
Single lesion single dose treatment of leprosy utilizes ROM therapy.
R: Rifampicin
O: Ofloxacin
M: Minocycline Nowdays, even single lesion leprosy is treated as paucibacillary leprosy
134. Ans. (b) Sparfloxacin (Ref: Principles of Pharmacology by KK Sharma and HL Sharma/734; KDT 6/e p692)
• Maximum phototoxic fluoroquinolone is sparfloxacin.
• Pefloxacin and Lomefloxacin are also phototoxic but less than sparfloxacin.
135. Ans. (c) Converted to formaldehyde at low pH (Ref: KDT 6/e p735)
Methanamine mandelate is used as an urinary antiseptic. It acts by conversion to formaldehyde at acidic urinary pH.
Mandelic acid formed from this salt also serves the function of urinary acidifying agent. These are not effective against
proteus because proteus results in the formation of ammonia which alkalinizes the urine.
136. Ans. (a) Epilepsy (Ref: KDT 6/e p689)
• Ciprofloxacin is contraindicated with NSAIDs because this combination results in increased risk of seizures.
• It is also contra-indicated with theophylline because it increases the risk of theophylline toxicity by inhibiting its
metabolism.
• It is contra-indicated in pregnancy because it increases the risk of cartilage damage in newborn.
137. Ans. (c) Pneumocystis jiroveci (Ref: KDT 6/e p686, 687)
Cotrimoxazole is effective against Pneumocystis and toxoplasmosis.
138. Ans. (a) Ciprofloxacin inhibits theophylline metabolism (Ref: KDT 6/e p221)
Theophylline has a narrow margin of safety (low therapeutic index) Ciprofloxacin inhibits theophylline metabolism and
increases its plasma level leading to toxicity. Thus, ciprofloxacin should not be given to an asthmatic using theophylline.
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Chemotherapy A: General Considerations Pharmacology and Non-specific...
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