Ambroxol 30 mg, Desloratadine 2.5 mg, Guaifenesin 50 mg, Menthol 1 mg / 5 ml Syrup

Desloratadine is a long-acting tricyclic histamine antagonist with selective H1-receptor histamine antagonist activity. Receptor binding data indicates that at a concentration of 2-3 ng/mL (7 nanomolar), desloratadine shows significant interaction with the human histamine H1-receptor.

Desloratadine inhibited histamine release from human mast cells in vitro. Results of a radiolabeled tissue distribution study in rats and a radioligand H1- receptor binding study in guinea pigs showed that desloratadine did not readily cross the blood brain barrier. The clinical significance of this finding is unknown.

Absorption: Following oral administration of a desloratadine 5 mg tablet once daily for 10 days to normal healthy volunteers, the mean time to maximum plasma concentrations (Tmax) occurred at approximately 3 hours post dose and mean steady state peak plasma concentrations (Cmax) and AUC of 4 ng/mL and 56.9 ng∙hr/mL were observed, respectively. Neither food nor grapefruit juice had an effect on the bioavailability (Cmax and AUC) of desloratadine.

The pharmacokinetic profile of desloratadine oral solution was evaluated in a three-way crossover study in 30 adult volunteers. A single dose of 10 mL of desloratadine oral solution containing 5 mg of desloratadine was bioequivalent to a single dose of 5 mg desloratadine tablet. Food had no effect on the bioavailability (AUC and Cmax) of desloratadine oral solution.

Distribution: Desloratadine and 3-hydroxydesloratadine are approximately 82% to 87% and 85% to 89% bound to plasma proteins, respectively. Protein binding of desloratadine and 3-hydroxydesloratadine was unaltered in subjects with impaired renal function.

Metabolism: Desloratadine (a major metabolite of loratadine) is extensively metabolized to 3-hydroxydesloratadine, an active metabolite, which is subsequently glucuronidated. The enzyme(s) responsible for the formation of 3-hydroxydesloratadine have not been identified. Data from clinical trials indicate that a subset of the general population has a decreased ability to form 3-hydroxydesloratadine, and are poor metabolizers of desloratadine. In pharmacokinetic studies (n=3,748), approximately 6% of subjects were poor metabolizers of desloratadine (defined as a subject with an AUC ratio of 3-hydroxydesloratadine to desloratadine less than 0.1, or a subject with a desloratadine half-life exceeding 50 hours). These pharmacokinetic studies included subjects between the ages of 2 and 70 years, including 977 subjects aged 2 to 5 years, 1,575 subjects aged 6 to 11 years, and 1196 subjects aged 12 to 70 years. There was no difference in the prevalence of poor metabolizers across age groups. The frequency of poor metabolizers was higher in Blacks (17%, n=988) as compared to Caucasians (2%, n=1,462) and Hispanics (2%, n=1,063). The median exposure (AUC) to desloratadine in the poor metabolizers was approximately 6-fold greater than in the subjects who are not poor metabolizers. Subjects who are poor metabolizers of desloratadine cannot be prospectively identified and will be exposed to higher levels of desloratadine following dosing with the recommended dose of desloratadine. In multidose clinical safety studies, where metabolizer status was identified, a total of 94 poor metabolizers and 123 normal metabolizers were enrolled and treated with desloratadine oral solution for 15 to 35 days. In these studies, no overall differences in safety were observed between poor metabolizers and normal metabolizers. Although not seen in these studies, an increased risk of exposure-related adverse events in patients who are poor metabolizers cannot be ruled out.

Elimination: The mean plasma elimination half-life of desloratadine was approximately 27 hours. Cmax and AUC values increased in a dose proportional manner following single oral doses between 5 and 20 mg. The degree of accumulation after 14 days of dosing was consistent with the half-life and dosing frequency. A human mass balance study documented a recovery of approximately 87% of the 14C-desloratadine dose, which was equally distributed in urine and feces as metabolic products. Analysis of plasma 3-hydroxydesloratadine showed similar Tmax and half-life values compared to desloratadine.

Special Populations — Geriatric Subjects: In older subjects (≥65 years old; n=17) following multiple-dose administration of desloratadine tablets, the mean Cmax and AUC values for desloratadine were 20% greater than in younger subjects (<65 years old). The oral total body clearance (CL/F) when normalized for body weight was similar between the two age groups. The mean plasma elimination half-life of desloratadine was 33.7 hr in subjects ≥ 65 years old. The pharmacokinetics for 3-hydroxydesloratadine appeared unchanged in older versus younger subjects. These age-related differences are unlikely to be clinically relevant and no dosage adjustment is recommended in elderly subjects.

Ambroxol is a bromhexine metabolite with secretolytic and secretomotor activity described in the oral-solution product information. Its full mechanism is not completely established. The separate HPRA lozenge reference also describes sodium-channel blockade in laboratory studies, a mechanism related to local anesthetic activity.

The oral-reference studies summarized by HPRA report peak plasma levels after approximately 1–2.5 hours for immediate-release ambroxol, protein binding of about 90% and a terminal half-life of about 10 hours. Metabolism occurs mainly in the liver, including glucuronidation and CYP3A4-mediated pathways. Lozenge, syrup and modified-release formulations can produce different exposure.

The proposed expectorant mechanism involves gastric receptor stimulation and a reflex increase in respiratory fluid secretion, reducing mucus viscosity. The source presents this mechanism as a proposed explanation.

The cited product information reports oral absorption but limited pharmacokinetic evidence. A 600 mg study in healthy adults found a plasma peak near 15 minutes. In three healthy men given 600 mg, the estimated half-life was about 1 hour. Distribution data and specific studies in renal or hepatic impairment were unavailable in this reference.

The cited syrup information describes mild local anesthetic and antitussive properties of menthol.

Oral menthol is absorbed from the gastrointestinal tract. Hepatic hydroxylation is followed by glucuronide conjugation, with elimination in urine and bile. The source provides no human distribution measurements. These oral data do not describe skin application.