A comparative pharmacokinetic and pharmacodynamic study of conventional and sustained-release preparations of acebutolol in healthy volunteers

[Assessment for antihypertensive drug intake: How, where and when?]

AIM

Hypertension is a public health problem managed according to therapeutic strategies published in France by the Hauteautoritéde santé (HAS - French Health Authorities). For patients with resistant hypertension, related or not to a non-adherence, prescribers need to be sure the exposure is high enough to achieve the tensional target. Quantitative analysis of antihypertensive drugs in different biological matrices (blood/urine) is one possible solution. However, this involves determining the concentrations observed at standard doses and knowing how to interpret the measured concentrations. It is also necessary to identify medical laboratories that can assay antihypertensive drugs. This was the aim of our work.

METHODS

The main antihypertensive drugs recommended by the HAS have been listed. For each of them, we looked for published steady-state plasma/serum concentrations and quantities excreted in the urine at usual dosages. In addition, the elimination half-life and linear pharmacokinetic profile were specified for each antihypertensive agent measured in plasma/serum. Pharmacology-Toxicology laboratories in France likely to carry out assays were identified. The time taken to report the result and the cost of the analysis were also specified.

RESULTS

All of the afore-mentioned information has been collected and presented in a table. This can then be used to compare the plasma/serum concentration or the quantity measured in a patient's urine with the values reported in the literature. In cases where the blood sampling times differ between those of the patient and the published data, the patient's measured value is compared to the estimated value based on the published concentrations and pharmacokinetics.

CONCLUSION

Interpretation of the plasma/serum/urinary value measured or estimated for an antihypertensive drug is a particularly interesting approach to determine if drug exposure is enough and a possible non-adherence. However, this activity is mostly carried out in hospital centres.

Effect of lipophilicity on in vivo iontophoretic delivery. II. Beta-blockers

The objective of this study was to investigate the relationship between drug lipophilicity and the transdermal absorption processes in the iontophoretic delivery in vivo. Anodal iontophoresis of beta-blockers as model drugs having different lipophilicity (atenolol, pindolol, metoprolol, acebutolol, oxprenolol and propranolol) was performed with rats (electrical current, 0.625 mA/cm2; application period, 90 min), and the drug concentrations in skin, cutaneous vein and systemic vein were determined. Increasing the lipophilicity of beta-blockers caused a greater absorption into the skin. Exceptionally, it was found that pindolol had high skin absorption, irrespective of its hydrophilic nature. Further, the drug transfer rate from skin to cutaneous vein (R(SC)) was evaluated from the arterio-venous plasma concentration difference of drug in the skin. Normalized R(SC) by skin concentration showed a negative correlation with the logarithm of n-octanol/buffer partition coefficient (Log P, pH 7.4), suggesting the partitioning between stratum corneum and viable epidermis was a primary process to determine the transfer properties of beta-blockers to local blood circulation. Pindolol exhibited both high skin absorption and high transfer from skin to cutaneous vein. These characteristics of pindolol could be explained by the chemical structure, molecular size and hydrophilicity. These findings for pindolol should be valuable for the optimal design of drug candidates for iontophoretic transdermal delivery.