Propylene glycol is an excipient of various pharmaceutical preparations. The pharmacokinetics after rectal administration are studied, followed by a consideration on local and systemic side-effects for a solution of paracetamol in a mixture of propylene glycol and water. After administration of 8.64 g propylene glycol to 10 adults and 173 mg/kg body weight to 4 children, peak concentrations (Cmax) of 199 mg/l and 171 mg/l respectively were reached (tmax) after 1.5 hr and 1.0 hr. The average terminal half-lives (t1/2) in adults and children were respectively 2.8 hr and 2.6 hr, total body clearance (CI/F) 0.20 l/hr*kg and 0.21 l/h*kg and apparent volume of distribution (VD/F) 0.79 l/kg and 0.77 l/kg.
A rapid high-resolution high pressure liquid chromatographic method was developed for assaying pilocarpine. Pilocarpine in ophthalmic solutions decomposes fairly rapidly to give isopilocarpine, pilocarpic acid and isopilocarpic acid. The quality of an ophthalmic solution can be assessed by assaying these decomposition products. Existing high pressure liquid chromatographic methods suffer from long analysis times and poor resolution. The new method uses as the mobile phase 6 ml/l of triethylamine in water (pH 2.3, adjusted with 85% phosphoric acid) at a flow of 1.5 ml/min and as the stationary phase a C18-silica 125 x 4.6 mm column. 2-Amino-1-phenyl-1,3-propanediol is used as an internal standard. Complete separation was obtained within 8 min. Pilocarpine eye drops were stored under different conditions and then analysed for decomposition products. During heat treatment, decomposition to isopilocarpine predominated over decomposition to pilocarpic or isopilocarpic acid. However, when stored at room temperature or in a refrigerator, formation of pilocarpic acid clearly prevailed. Thus, from assessment of decomposition products, the cause of decomposition can be established.
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