Pharmacokinetics and metabolism of N-(2-hydroxyethyl)-2,5-[14C]-pyrrolidine (HEP, Epolamine) in male healthy volunteers

Predicting topical drug clearance from the skin

For topical drug products that target sites of action in the viable epidermal and/or upper dermal compartment of the skin, the local concentration profiles have proven difficult to quantify because drug clearance from the viable cutaneous tissue is not well characterised. Without such knowledge, of course, it is difficult-if not impossible-to predict a priori whether and over what time frame a topical formulation will permit an effective concentration of drug within the skin 'compartment' to be achieved. Here, we test the hypothesis that valuable information about drug disposition, and specifically its clearance, in this experimentally difficult-to-access compartment (at least, in vivo) can be derived from available systemic pharmacokinetic data for drugs administered via transdermal delivery systems. A multiple regression analysis was undertaken to determine the best-fit empirical correlation relating clearance from the skin to known or easily calculable drug properties. It was possible, in this way, to demonstrate a clear relationship between drug clearance from the skin and key physical chemical properties of the drug (molecular weight, log P and topological polar surface area). It was further demonstrated that values predicted by the model correlated well with those derived from in vitro skin experiments.

Diclofenac salts, part 7: are the pharmaceutical salts with aliphatic amines stable?

Eight cyclic aliphatic amines, pyrrolidine (Py), piperidine (Pp), morpholine (M), piperazine (Pz), and the N-hydroxyethyl (HE) analogues, were employed to prepare a salt with acidic diclofenac (D). These salts were examined by thermal [differential scanning calorimetry (DSC), thermogravimetric analysis, and hot-stage microscopy (HSM)] and spectroscopic [Fourier transform infrared (FTIR), Raman, (1) H NMR, and ultraviolet] analysis. The results show the thermal instability of these salts: the thermal dissociation leaves the starting acidic D, evidenced by the FTIR and Raman spectra inside the molten mass of the salts with M and HEM. The nature of the salt with Pz (1:1 or 1:2) and HEPy (anhydrous or hydrate polymorph), but not for the salt with HEPz and Py, depends on the polarity of the solvent used for the preparation of the salt. Incomplete dehydration of the hydrate Py and Pz salts progressively modifies the thermogram profiles and originates false information. Melting of the salts with Pp, M, and HEM could be demonstrated by HSM, but not with DSC. The difficulty of providing a description of these salts in a simple way originates doubts on the utility of a wide application of aliphatic amines to prepare pharmaceutical salts with D, whose solubility in water does not significantly differ from that of the common sodium D.

Topical diclofenac: clinical effectiveness and current uses in osteoarthritis of the knee and soft tissue injuries

BACKGROUND

Diclofenac is a commonly used non-steroidal anti-inflammatory drug (NSAID) for symptom control in osteoarthritis (OA) of the knee and soft tissue injuries. Although treatment with oral diclofenac is associated with serious adverse effects involving both the gastrointestinal and renal systems, these adverse effects are thought to be limited with topical diclofenac formulations without loss of efficacy.

OBJECTIVE

The aim of this review is to explore the available evidence in relation to the pharmacokinetics, efficacy and reported adverse effects of the topical diclofenac formulations available.

RESULTS/CONCLUSIONS

In the majority of studies examined, topical diclofenac formulations with sodium lotion, lecithin or epolamine gel, patch or plaster were either superior or equivalent to oral diclofenac formulations or placebo. Topical diclofenac significantly reduced pain and morning stiffness and improved physical function and patient global assessment without major adverse effects reported in patients with OA of the knee; and provided significant pain relief in patients with sports and soft tissue injuries involving the ankle, knee or shoulder. In the majority of studies, the predominant adverse effect involved pruritus or rash at the site of application, or nausea. The principle outcome of these studies is that topical diclofenac is a safe and practical alternative as a method of treatment in OA of the knee or as an alternative treatment for sports and soft tissue injury.