Clarisdase Actions

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• Actions of Clarisdase in details
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• Clarisdase pharmacology
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Actions of Clarisdase in details

Pharmacology: Mechanism of Action: Clarisdase and other macrolides bind reversibly to the 50S subunit of the ribosome, resulting in blockage of the transpeptidation or translocation reactions, inhibition of protein synthesis, and hence inhibition of cell growth. Its action is predominantly bacteriostatic, but high concentrations are slowly bactericidal against the more sensitive strains. Because macrolides penetrate readily into white blood cells and macrophages, there has been some interest in their potential synergy with the host defense mechanism in vivo.

Microbiology: Clarisdase is reported to be more active than erythromycin against susceptible streptococci and staphylococci in vitro, as well as against some other species including Moraxella catarrhalis (Branhamella catarrhalis), Legionella spp, Chlamydia trachomatis and Ureaplasma urealyticum. Clarisdase is reported to be more active than erythromycin or azithromycin against some mycobacteria, including Mycobacterium avium complex and against M. leprae. It is reported to have some in vitro activity against the protozoan Toxoplasma gondii, and may have some activity against cryptosporidia. The major metabolite, 14-hydroxyclarithromycin, is also active, and may enhance the activity of Clarisdase in vivo, notably against Haemophilus influenzae.

Pharmacokinetics: Clarisdase is rapidly and well absorbed from the gastrointestinal tract after oral administration of Clarisdase tablets. The microbiologically active metabolite, 14-hydroxyclarithromycin, is formed by first-pass metabolism. Clarisdase may be given without regard to meals as food does not affect the extent of bioavailability of Clarisdase tablets. Food does slightly delay the onset of absorption of Clarisdase and formation of the 14-hydroxymetabolite.

The kinetics of orally administered modified-release Clarisdase have been studied in adult humans and compared with Clarisdase 250 and 500 mg immediate-release tablets. The extent of absorption was found to be equivalent when equal total daily doses were administered. The absolute bioavailability is approximately 50%.

Urinary excretion accounted for approximately 40% of the Clarisdase dose. Fecal elimination accounts for approximately 30%.

Clarisdase also penetrates the gastric mucus. Levels of Clarisdase in gastric mucus and gastric tissue are higher when Clarisdase is co-administered with omeprazole than when Clarisdase is administered alone.

How should I take Clarisdase?

Take Clarisdase exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

You may take the tablets and oral suspension (liquid) with or without food.

Clarisdase extended-release tablets (Biaxin XL) should be taken with food.

Do not crush, chew, or break an extended-release tablet. Swallow it whole.

Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

Use this medicine for the full prescribed length of time. Clarisdase is usually given for up to 7 to 14 days. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Clarisdase will not treat a viral infection such as the flu or a common cold.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

Do not keep the oral liquid in a refrigerator. Throw away any liquid that has not been used within 14 days.

Clarisdase administration

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

You may take Clarisdase tablets and oral suspension (liquid) with or without food.

Clarisdase extended-release tablets (Biaxin XL) should be taken with food.

Do not crush, chew, or break an extended-release tablet. Swallow it whole. Breaking the pill may cause too much of the drug to be released at one time.

Shake the oral suspension (liquid) well just before you measure a dose. Measure the liquid with a special dose-measuring spoon or medicine cup, not with a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.

Take this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Clarisdase will not treat a viral infection such as the common cold or flu.

Store at room temperature away from moisture and heat. Do not keep the oral liquid in a refrigerator.

Clarisdase pharmacology

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Mechanism of Action

Clarisdase is a macrolide antimicrobial drug.

Pharmacokinetics

Absorption

Clarisdase Immediate-Release Tablets

The absolute bioavailability of 250 mg Clarisdase tablets was approximately 50%. For a single 500 mg dose of Clarisdase, food slightly delays the onset of Clarisdase absorption, increasing the peak time from approximately 2 to 2.5 hours. Food also increases the Clarisdase peak plasma concentration by about 24%, but does not affect the extent of Clarisdase bioavailability. Food does not affect the onset of formation of the active metabolite, 14-OH Clarisdase or its peak plasma concentration but does slightly decrease the extent of metabolite formation, indicated by an 11% decrease in area under the plasma concentration-time curve (AUC). Therefore, Clarisdase tablets may be given without regard to food. In non-fasting healthy human subjects (males and females), peak plasma concentrations were attained within 2 to 3 hours after oral dosing.

Clarisdase Extended-Release Tablets

Clarisdase extended-release tablets provide extended absorption of Clarisdase from the gastrointestinal tract after oral administration. Relative to an equal total daily dose of immediate-release Clarisdase tablets, Clarisdase extended-release tablets provide lower and later steady-state peak plasma concentrations but equivalent 24 hour AUCs for both Clarisdase and its microbiologically-active metabolite, 14-OH Clarisdase. While the extent of formation of 14-OH Clarisdase following administration of Clarisdase extended-release tablets (2 x 500 mg tablets once daily) is not affected by food, administration under fasting conditions is associated with approximately 30% lower Clarisdase AUC relative to administration with food. Therefore, Clarisdase extended-release tablets should be taken with food.

Figure 2: Steady-State Clarisdase Plasma Concentration-Time Profiles

Clarisdase for

Oral Suspension

When 250 mg doses of Clarisdase as Clarisdase suspension were administered to fasting healthy adult subjects, peak plasma concentrations were attained around 3 hours after dosing.

For adult patients, the bioavailability of 10 mL of the 125 mg/5 mL suspension or 10 mL of the 250 mg/5 mL suspension is similar to a 250 mg or 500 mg tablet, respectively.

In adults given 250 mg Clarisdase as suspension (n = 22), food appeared to decrease mean peak plasma Clarisdase concentrations from 1.2 (± 0.4) mcg/mL to 1.0 (± 0.4) mcg/mL and the extent of absorption from 7.2 (± 2.5) hr•mcg/mL to 6.5 (± 3.7) hr•mcg/mL.

Distribution

Clarisdase and the 14-OH Clarisdase metabolite distribute readily into body tissues and fluids. There are no data available on cerebrospinal fluid penetration. Because of high intracellular concentrations, tissue concentrations are higher than serum concentrations. Examples of tissue and serum concentrations are presented below.

Table 9. Tissue and Serum Concentrations of Clarisdase

Metabolism and Elimination

Clarisdase Immediate-Release Tablets

Steady-state peak plasma Clarisdase concentrations were attained within 3 days and were approximately 1 mcg/mL to 2 mcg/mL with a 250 mg dose administered every 12 hours and 3 mcg/mL to 4 mcg/mL with a 500 mg dose administered every 8 hours to 12 hours. The elimination half-life of Clarisdase was about 3 hours to 4 hours with 250 mg administered every 12 hours but increased to 5 hours to 7 hours with 500 mg administered every 8 hours to 12 hours. The nonlinearity of Clarisdase pharmacokinetics is slight at the recommended doses of 250 mg and 500 mg administered every 8 hours to 12 hours. With a 250 mg every 12 hours dosing, the principal metabolite, 14-OH Clarisdase, attains a peak steady-state concentration of about 0.6 mcg/mL and has an elimination half-life of 5 hours to 6 hours. With a 500 mg every 8 hours to 12 hours dosing, the peak steady-state concentration of 14-OH Clarisdase is slightly higher (up to 1 mcg/mL), and its elimination half-life is about 7 hours to 9 hours. With any of these dosing regimens, the steady-state concentration of this metabolite is generally attained within 3 days to 4 days.

After a 250 mg tablet every 12 hours, approximately 20% of the dose is excreted in the urine as Clarisdase, while after a 500 mg tablet every 12 hours, the urinary excretion of Clarisdase is somewhat greater, approximately 30%. In comparison, after an oral dose of 250 mg (125 mg/5 mL) suspension every 12 hours, approximately 40% is excreted in urine as Clarisdase. The renal clearance of Clarisdase is, however, relatively independent of the dose size and approximates the normal glomerular filtration rate. The major metabolite found in urine is 14-OH Clarisdase, which accounts for an additional 10% to 15% of the dose with either a 250 mg or a 500 mg tablet administered every 12 hours.

Clarisdase Extended-Release Tablets

In healthy human subjects, steady-state peak plasma Clarisdase concentrations of approximately 2 mcg/mL to 3 mcg/mL were achieved about 5 hours to 8 hours after oral administration of 1,000 mg Clarisdase extended-release tablets once daily; for 14-OH Clarisdase, steady-state peak plasma concentrations of approximately 0.8 mcg/mL were attained about 6 hours to 9 hours after dosing. Steady-state peak plasma Clarisdase concentrations of approximately 1 mcg/mL to 2 mcg/mL were achieved about 5 hours to 6 hours after oral administration of a single 500 mg Clarisdase extended-release tablets once daily; for 14-OH Clarisdase, steady-state peak plasma concentrations of approximately 0.6 mcg/mL were attained about 6 hours after dosing.

Steady-state peak plasma concentrations were attained in 2 days to 3 days and were approximately 2 mcg/mL for Clarisdase and 0.7 mcg/mL for 14-OH Clarisdase when 250 mg doses of the Clarisdase suspension were administered every 12 hours. Elimination half-life of Clarisdase (3 hours to 4 hours) and that of 14-OH Clarisdase (5 hours to 7 hours) were similar to those observed at steady state following administration of equivalent doses of Clarisdase tablets.

Specific Populations for Clarisdase Tablets, Clarisdase Extended-Release Tablets, and Clarisdase for

Oral Suspension Formulations

Clarisdase for

Oral Suspension in Pediatric Patients

Clarisdase penetrates into the middle ear fluid of pediatric patients with secretory otitis media.

Table 10. Middle Ear Fluid and Serum Concentrations of Clarisdase and 14-OH- Clarisdase in Pediatric Patients

When pediatric patients (n = 10) were administered a single oral dose of 7.5 mg/kg Clarisdase as an oral suspension, food increased mean peak plasma Clarisdase concentrations from 3.6 (±1.5) mcg/mL to 4.6 (± 2.8) mcg/mL and the extent of absorption from 10.0 (± 5.5) hr•mcg/mL to 14.2 (± 9.4) hr•mcg/mL.

In pediatric patients requiring antibacterial therapy, administration of 7.5 mg/kg every 12 hours of Clarisdase as an oral suspension generally resulted in steady-state peak plasma concentrations of 3 mcg/mL to 7 mcg/mL for Clarisdase and 1 mcg/mL to 2 mcg/mL for 14-OH Clarisdase.

In HIV-infected pediatric patients taking 15 mg/kg of Clarisdase as an oral suspension every 12 hours, steady-state Clarisdase peak concentrations generally ranged from 6 mcg/mL to 15 mcg/mL.

HIV Infection

Steady-state concentrations of Clarisdase and 14-OH Clarisdase observed following administration of 500 mg doses of Clarisdase every 12 hours to adult patients with HIV infection were similar to those observed in healthy volunteers. In adult HIV-infected patients taking 500 mg or 1,000 mg doses of Clarisdase every 12 hours, steady-state Clarisdase Cmax values ranged from 2 mcg/mL to 4 mcg/mL and 5 mcg/mL to 10 mcg/mL, respectively.

Hepatic Impairment

The steady-state concentrations of Clarisdase in subjects with impaired hepatic function did not differ from those in normal subjects; however, the 14-OH Clarisdase concentrations were lower in the hepatically impaired subjects. The decreased formation of 14-OH Clarisdase was at least partially offset by an increase in renal clearance of Clarisdase in the subjects with impaired hepatic function when compared to healthy subjects.

Renal Impairment

The pharmacokinetics of Clarisdase was also altered in subjects with impaired renal function.

Drug Interactions

Fluconazole

Following administration of fluconazole 200 mg daily and Clarisdase 500 mg twice daily to 21 healthy volunteers, the steady-state Clarisdase Cmin and AUC increased 33% and 18%, respectively. Clarisdase exposures were increased and steady-state concentrations of 14-OH Clarisdase were not significantly affected by concomitant administration of fluconazole.

Colchicine

When a single dose of colchicine 0.6 mg was administered with Clarisdase 250 mg BID for 7 days, the colchicine Cmax increased 197% and the AUC0-∞ increased 239% compared to administration of colchicine alone.

Atazanavir

Following administration of Clarisdase (500 mg twice daily) with atazanavir (400 mg once daily), the Clarisdase AUC increased 94%, the 14-OH Clarisdase AUC decreased 70% and the atazanavir AUC increased 28%.

Ritonavir

Concomitant administration of Clarisdase and ritonavir (n = 22) resulted in a 77% increase in Clarisdase AUC and a 100% decrease in the AUC of 14-OH Clarisdase.

Saquinavir

Following administration of Clarisdase (500 mg bid) and saquinavir (soft gelatin capsules, 1200 mg tid) to 12 healthy volunteers, the steady-state saquinavir AUC and Cmax increased 177% and 187% respectively compared to administration of saquinavir alone. Clarisdase AUC and Cmax increased 45% and 39% respectively, whereas the 14–OH Clarisdase AUC and Cmax decreased 24% and 34% respectively, compared to administration with Clarisdase alone.

Didanosine

Simultaneous administration of Clarisdase tablets and didanosine to 12 HIV-infected adult patients resulted in no statistically significant change in didanosine pharmacokinetics.

Zidovudine

Following administration of Clarisdase 500 mg tablets twice daily with zidovudine 100 mg every 4 hours, the steady-state zidovudine AUC decreased 12% compared to administration of zidovudine alone (n=4). Individual values ranged from a decrease of 34% to an increase of 14%. When Clarisdase tablets were administered two to four hours prior to zidovudine, the steady- state zidovudine Cmax increased 100% whereas the AUC was unaffected (n=24).

Omeprazole

Clarisdase 500 mg every 8 hours was given in combination with omeprazole 40 mg daily to healthy adult subjects. The steady-state plasma concentrations of omeprazole were increased (Cmax, AUC0-24, and t½ increases of 30%, 89%, and 34%, respectively), by the concomitant administration of Clarisdase.

The plasma levels of Clarisdase and 14–OH Clarisdase were increased by the concomitant administration of omeprazole. For Clarisdase, the mean Cmax was 10% greater, the mean Cmin was 27% greater, and the mean AUC0-8 was 15% greater when Clarisdase was administered with omeprazole than when Clarisdase was administered alone. Similar results were seen for 14–OH Clarisdase, the mean Cmax was 45% greater, the mean Cmin was 57% greater, and the mean AUC0-8 was 45% greater. Clarisdase concentrations in the gastric tissue and mucus were also increased by concomitant administration of omeprazole.

Theophylline

In two studies in which theophylline was administered with Clarisdase (a theophylline sustained-release formulation was dosed at either 6.5 mg/kg or 12 mg/kg together with 250 or 500 mg q12h Clarisdase), the steady-state levels of Cmax, Cmin, and the area under the serum concentration time curve (AUC) of theophylline increased about 20%.

Midazolam

When a single dose of midazolam was coadministered with Clarisdase tablets (500 mg twice daily for 7 days), midazolam AUC increased 174% after intravenous administration of midazolam and 600% after oral administration.

For information about other drugs indicated in combination with Clarisdase, refer to their full prescribing information, CLINICAL PHARMACOLOGY section.

Microbiology

Mechanism of Action

Clarisdase exerts its antibacterial action by binding to the 50S ribosomal subunit of susceptible bacteria resulting in inhibition of protein synthesis.

Resistance

The major routes of resistance are modification of the 23S rRNA in the 50S ribosomal subunit to insensitivity or drug efflux pumps. Beta-lactamase production should have no effect on Clarisdase activity.

Most isolates of methicillin-resistant and oxacillin-resistant staphylococci are resistant to Clarisdase.

If H. pylori is not eradicated after treatment with Clarisdase-containing combination regimens, patients may develop Clarisdase resistance in H. pylori isolates. Therefore, for patients who fail therapy, Clarisdase susceptibility testing should be done, if possible. Patients with Clarisdase-resistant H. pylori should not be treated with any of the following: omeprazole/Clarisdase dual therapy; omeprazole/Clarisdase/amoxicillin triple therapy; lansoprazole/Clarisdase/amoxicillin triple therapy; or other regimens which include Clarisdase as the sole antibacterial agent.

Antimicrobial Activity

Clarisdase has been shown to be active against most of the isolates of the following microorganisms both in vitro and in clinical infections.

Gram-Positive Bacteria

• Staphylococcus aureus
• Streptococcus pneumoniae
• Streptococcus pyogenes

Gram-Negative Bacteria

• Haemophilus influenzae
• Haemophilus parainfluenzae
• Moraxella catarrhalis

Other Microorganisms

• Chlamydophila pneumoniae
• Helicobacter pylori
• Mycobacterium avium complex (MAC) consisting of M. avium and M. intracellulare
• Mycoplasma pneumoniae

At least 90 percent of the microorganisms listed below exhibit in vitro minimum inhibitory concentrations (MICs) less than or equal to the Clarisdase susceptible MIC breakpoint for organisms of similar type to those shown in Table 11. However, the efficacy of Clarisdase in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials.

Gram-Positive Bacteria

• Streptococcus agalactiae
• Streptococci (Groups C, F, G)
• Viridans group streptococci

Gram-Negative Bacteria

• Legionella pneumophila
• Pasteurella multocida

Anaerobic Bacteria

• Clostridium perfringens
• Peptococcus niger
• Prevotella melaninogenica
• Propionibacterium acnes

Susceptibility Testing Methods (Excluding Mycobacteria and Helicobacter)

When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drugs used in local hospitals and practice areas to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antimicrobial drug for treatment.

Dilution Techniques

Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method1,2 (broth and/or agar). The MIC values should be interpreted according to the criteria provided in Table 11.

Diffusion Techniques

Quantitative methods that require measurement of zone diameters can also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized test method.2,3 This procedure uses paper disks impregnated with 15 mcg of Clarisdase to test the susceptibility of bacteria to Clarisdase. The disk diffusion interpretive criteria are provided in Table 11.

Susceptibility Testing for Mycobacterium avium Complex (MAC)

The reference methodology for susceptibility testing of Mycobacterium avium complex (MAC) is broth dilution (either microdilution or macrodilution method).4 For broth microdilution testing, cation-adjusted Mueller-Hinton broth (CAMHB) supplemented with 5% OADC is recommended. Transparent colonies should be used for the inoculum, if present. Susceptibility testing at either pH 6.8 or pH 7.4 is acceptable, provided that interpretation is done based on the culture conditions employed. Microdilution trays are incubated at 35 ºC to 37 ºC in ambient air and examined after seven days. Trays should be incubated and read again at 10 to 14 days, if growth is poor on initial inspection.

Susceptibility Testing for Helicobacter pylori

The reference methodology for susceptibility testing of H. pylori is agar dilution MICs.5 One to three microliters of an inoculum equivalent to a No. 2 McFarland standard (1 x 107-1 x 108 CFU/mL for H. pylori) are inoculated directly onto freshly prepared antimicrobial containing Mueller-Hinton agar plates with 5% aged defibrinated sheep blood (> 2 weeks old). The agar dilution plates are incubated at 35°C in a microaerobic environment produced by a gas generating system suitable for Campylobacter species. After 3 days of incubation, the MICs are recorded as the lowest concentration of antimicrobial agent required to inhibit growth of the organism. The Clarisdase MIC values should be interpreted according to the criteria in Table 11.

Table 11. Susceptibility Test Interpretive Criteria for Clarisdase

A report of Susceptible (S) indicates that the antimicrobial drug is likely to inhibit growth of the pathogen if the antimicrobial drug reaches the concentration usually achievable at the site of infection. A report of Intermediate (I) indicates that the result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of Resistant (R) indicates that the antimicrobial drug is not likely to inhibit growth of the pathogen if the antimicrobial drug reaches the concentration usually achievable at the infection site; other therapy should be selected.

Quality Control

Standardized susceptibility test procedures require the use of laboratory control bacteria to monitor and ensure the accuracy and precision of supplies and reagents in the assay, and the techniques of the individual performing the test.1 to 5 Standard Clarisdase powder should provide the following range of MIC values as noted in Table 12. For the diffusion technique using the 15 mcg disk, the criteria in Table 12 should be achieved.

Table 12. Acceptable Quality Control Ranges for Clarisdase

References

1. DailyMed. "CLARITHROMYCIN: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
2. NCIt. "Clarithromycin: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". https://ncit.nci.nih.gov/ncitbrowser... (accessed September 17, 2018).
3. EPA DSStox. "Clarithromycin: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).

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Information checked by Dr. Sachin Kumar, MD Pharmacology