What is Clarex, and how does it work (mechanism of action)?
Clarex is a semi-synthetic macrolide antibiotic chemically related to erythromycin and azithromycin (Zithromax). It is effective against a wide variety of bacteria, such as Haemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Staphylococcus aureus, and mycobacterium avium, and many others. Like all macrolide antibiotics, Clarex prevents bacteria from growing by interfering with their ability to make proteins. Due to the differences in the way proteins are made in bacteria and humans, the macrolide antibiotics do not interfere with production of proteins in humans. The FDA approved Clarex in October 1991.
Rated Clarex for Upper Respiratory Tract Infection Report
It’s good as an alternative to penicillin if you’re allergic & it works great! But, be prepared to have diarrhea at some point on it. I seem to have diarrhea every time I am on this antibiotic.
Clarex and the 14-OH Clarex 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 Clarex
What should I tell my health care provider before taking Clarex?
Before taking Clarex, tell your health care provider:
- If you are allergic to Clarex or any other medicines.
- About any medical conditions you have or have had.
- About anything that could affect your ability to take medicines, such as difficulty swallowing or remembering to take pills. A liquid form of Clarex is available for people who have difficulty swallowing pills.
- If you are pregnant or plan to become pregnant. Clarex should not be used during pregnancy except when there are no other treatment options. Talk to your health care provider about the risks of taking Clarex during pregnancy.
- If you are breastfeeding or plan to breastfeed. Do not breastfeed if you have HIV.
- About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Clarex may affect the way other medicines or products work, and other medicines or products may affect how Clarex works. Ask your health care provider if there are interactions between Clarex and the other medicines you take.
Ask your health care provider about possible side effects from Clarex. Your health care provider will tell you what to do if you have side effects.
Before taking this medicine
You should not use this medicine if you are allergic to Clarex or similar medicines such as azithromycin (Zithromax, Z-Pak, Zmax), erythromycin, or telithromycin, or if:
you have had jaundice or liver problems caused by taking Clarex; or
you have liver or kidney disease and you also take a medicine called colchicine.
Some medicines can cause unwanted or dangerous effects when used with Clarex. Your doctor may need to change your treatment plan if you use any of the following drugs:
To make sure this medicine is safe for you, tell your doctor if you have ever had:
long QT syndrome (in you or a family member);
an electrolyte imbalance (such as low levels of potassium or magnesium in your blood).
Clarex may harm an unborn baby. Use effective birth control to prevent pregnancy while you are using this medicine. Tell your doctor if you become pregnant.
In animal studies, Clarex caused birth defects. However, it is not known whether these effects would occur in humans. Ask your doctor about your risk.
Clarex can pass into breast milk and may cause side effects in the nursing baby. Tell your doctor if you are breast-feeding.
This medicine is not approved for use by anyone younger than 6 months old.
Clarex oral tablet doesn’t cause drowsiness. However, it can cause other side effects.
Co-administration of BIAXIN is known to inhibit CYP3A, and a drug primarily metabolized by CYP3A may be associated with elevations in drug concentrations that could increase or prolong both therapeutic and adverse effects of the concomitant drug.
BIAXIN should be used with caution in patients receiving treatment with other drugs known to be CYP3A enzyme substrates, especially if the CYP3A substrate has a narrow safety margin (e.g., carbamazepine) and/or the substrate is extensively metabolized by this enzyme. Adjust dosage when appropriate and monitor serum concentrations of drugs primarily metabolized by CYP3A closely in patients concurrently receiving Clarex.
Table 8: Clinically Significant Drug Interactions with BIAXIN
BIAXIN Filmtab Immediate-Release Tablets
The absolute bioavailability of 250 mg Clarex tablets was approximately 50%. For a single 500 mg dose of Clarex, food slightly delays the onset of Clarex absorption, increasing the peak time from approximately 2 to 2.5 hours. Food also increases the Clarex peak plasma concentration by about 24%, but does not affect the extent of Clarex bioavailability. Food does not affect the onset of formation of the active metabolite, 14-OH Clarex 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, BIAXIN Filmtab 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.
BIAXIN XL Filmtab Extended-Release Tablets
Clarex extended-release tablets provide extended absorption of Clarex from the gastrointestinal tract after oral administration. Relative to an equal total daily dose of immediate-release Clarex tablets, Clarex extended-release tablets provide lower and later steady-state peak plasma concentrations but equivalent 24-hour AUCs for both Clarex and its microbiologically-active metabolite, 14-OH Clarex. While the extent of formation of 14-OH Clarex following administration of BIAXIN XL Filmtab (2 x 500 mg tablets once daily) is not affected by food, administration under fasting conditions is associated with approximately 30% lower Clarex AUC relative to administration with food. Therefore, BIAXIN XL Filmtab should be taken with food.
Figure 2: Steady-State Clarex Plasma Concentration-Time Profiles
BIAXIN Granules For Oral Suspension
When 250 mg doses of Clarex as BIAXIN as an oral 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 Clarex as suspension (n = 22), food appeared to decrease mean peak plasma Clarex 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.
BIAXIN Granules For Oral Suspension In Pediatric Patients
Clarex penetrates into the middle ear fluid of pediatric patients with secretory otitis media.
Table 10: Middle Ear Fluid and Serum Concentrations of Clarex and 14-OH-Clarex in Pediatric Patients
When pediatric patients (n = 10) were administered a single oral dose of 7.5 mg/kg BIAXIN as an oral suspension, food increased mean peak plasma Clarex 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 BIAXIN as an oral suspension generally resulted in steady-state peak plasma concentrations of 3 mcg/mL to 7 mcg/mL for Clarex and 1 mcg/mL to 2 mcg/mL for 14-OH Clarex.
In HIV-infected pediatric patients taking 15 mg/kg of BIAXIN as an oral suspension every 12 hours, steady-state Clarex peak concentrations generally ranged from 6 mcg/mL to 15 mcg/mL.
Steady-state concentrations of Clarex and 14-OH Clarex observed following administration of 500 mg doses of Clarex 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 1000-mg doses of Clarex every 12 hours, steady-state Clarex Cmax values ranged from 2 mcg/mL to 4 mcg/mL and 5 mcg/mL to 10 mcg/mL, respectively.
The steady-state concentrations of Clarex in subjects with impaired hepatic function did not differ from those in normal subjects; however, the 14-OH Clarex concentrations were lower in the hepatically impaired subjects. The decreased formation of 14-OH Clarex was at least partially offset by an increase in renal clearance of Clarex in the subjects with impaired hepatic function when compared to healthy subjects.
The pharmacokinetics of Clarex was also altered in subjects with impaired renal function .