Salbutamol urinary

Table 8.2 30-min post-inhalation urinary salbutamol excretion (% inhaled dose) in nine subjects following inhalation of 4 X 100 mg salbutamol using a metered-dose inhaler (MDI) and a dry powder inhaler (DISK) ... 

Hindle, M., Newton, D. A., and Chrystyn, H. (1993), Investigations of an optimal inhaler technique with the use of urinary salbutamol excretion as a measure of relative bioavailability to the lung, Thorax, 48, 607-610. 

A similar approach has been to measure plasma salbutamol levels at 30 min (129-132). These smdies have often included pharmacokinetic components, such as the effect of the beta agonist on heart rate tremor and serum potassium. A major problem with this approach is that multiple doses are required, with as many as 12 doses being nsed in the studies involving plasma levels to detect both the drug and the pharmacodynamic responses, while the urinary salbutamol method generally involves four inhalations. 

Hindle M, Newton DAG, Chrystyn H. Dry powder inhalers are bioequivalent to metered-dose inhalers a study using a new urinary albuterol (Salbutamol) assay technique. Chest 1995 107 629-633. 

Urinary tract Bladder relaxation is caused in part by p2 stimulation. A case was reported with a child, who suffered from urinary retention by salbutamol. 

A 2-year, 8-month-old child was referred to the hospital with complaint of urinary retention. The patient was prescribed salbutamol 4days ago for an episode of wheezing. The only abnormalities on the physical examination were small eczematous eruptions on his face and a full bladder. This was found by palpation and percussion... 

The other common conjugation reaction for hydroxyl groups in drags is sulphation. The sulphate group is transferred from 3 -phosphoadenosine-5 -phosphosulfate (PAPS) via the action of sulphotransferase. Figure 8.40 shows the formation of the sulphate of salbutamol which is the main urinary metabolite of the drag. 

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