Absorption
Bromhexine is rapidly and completely absorbed from the gastrointestinal tract.
After oral administration solid and liquid formulations show similar bioavailability. The absolute bioavailability of bromhexine hydrochloride was about 22.2 ± 8.5 % and 26.8 ± 13.1 % for BISOLVON® tablets and solution, respectively. The first pass metabolism amounts to about 75-80%. Concomitant food leads to an increase of bromhexine plasma concentrations.
Distribution
After intravenous administration bromhexine was rapidly and widely distributed throughout the body with a mean volume of distribution (Vss) of up to 1209 ± 206 L (19 L/kg). The distribution into lung tissue (bronchial and parenchymal) was investigated after oral administration of 32 mg and 64 mg bromhexine. Lung tissue concentrations two hours post dose 1.5 -4.5 times higher in bronchiolo-bronchial tissues and between 2.4 and 5.9 times higher in pulmonary parenchyma compared to plasma concentrations. Unchanged bromhexine is bound to plasma proteins by 95 % (non-restrictive binding).
Metabolism
Bromhexine is almost completely metabolised to a variety of hydroxylated metabolites and to dibromanthranilic acid. All metabolites and bromhexine itself are conjugated most probably in form of N-glucuronides and O-glucuronides. There are no substantial hints for a change of the metabolic pattern by a sulphonamide or oxytetracyclin. There is insufficient pharmacokinetic data to eva luate a possible drug-drug interaction between bromhexine and erythromycin.
Elimination
Bromhexine is a high extraction ratio drug after i.v. administration in the range of the hepatic blood flow, 843-1073 mL/min resulting in high inter- and intraindividual variability (CV > 30 %) After administration of radiolabelled bromhexine about 97.4 ± 1.9 % of the dose were recovered as radioactivity in urine, with less than 1% as parent compound.
Bromhexine plasma concentrations showed a multiexponential decline. After administration of single oral doses between 8 and 32 mg, the terminal elimination half-life ranged between 6.6 and 31.4 hours. The relevant half-life to predict the multiple dose pharmacokinetics is about 1 hour, thus no accumulation was seen after multiple dosing (accumulation factor 1.1).
General
Bromhexine shows dose proportional pharmacokinetics in the range of 8-32 mg following oral administration. There are no data for bromhexine pharmacokinetics in the elderly or in patients with renal or liver insufficiency.
Bromhexine pharmacokinetics are not relevantly affected by co-administration of ampicillin or oxytetracycline.
Interaction studies with oral anticoagulants or digoxin were not performed.
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