Nanoparticle delivery for transdermal HRT

Nanomedicine is an emerging technology and the first nano-engineered medical products have come to light in the last decade. Transdermal drug delivery has significant advantages compared to other routes of drug administration. Nanoparticles unique physical and chemical properties enable transport of substances directly into the skin. The objective of this paper is to review different aspects of nanoparticle delivery, generally, and discuss its current use for transdermal hormone therapy. Transdermal estrogen therapy remains the most effective treatment for bothersome menopausal symptoms, particularly in those women for whom the potential adverse effects associated with “first pass” hepatic metabolism are to be avoided. Available alternatives for transdermal estrogen delivery include patches, gels, sprays and lotions. Other non-oral therapies which likewise avoid “first pass” hepatic metabolism include: subcutaneous implants and vaginal rings. Some of the transdermal products are associated with mild adverse skin effects such as redness and irritation, but more severe and bothersome consequences include blistering and tattooing. Even the mild adverse skin effects are frequently cited as reasons for discontinuation. Micellar nanoparticle estradiol emulsion (MNPEE) is a lotion-like therapy which constitutes an alternative transdermal delivery system not requiring the permeation enhancers or temporary skin digestion, both of which increase the possibility of irritation. MNPEE's advantages include low fluctuation of plasma estradiol concentrations, infrequent skin related adverse effects, and pleasant cosmetic-like moisturizing properties. The efficacy of MNPEE for management of menopausal vasomotor symptoms has been demonstrated in a randomized placebo controlled trial,¹ and the product is FDA approved for management of moderate to severe vasomotor symptoms. None of the observed adverse effects in the MNPEE group were statistically different from the placebo group.¹ Studies addressing inadvertent transference of estradiol to the male partners of menopausal women using this delivery technology have demonstrated small, but real amounts of transference, which do not exceed the normal physiological male estradiol range. MNPEE is safe and effective for treatment of vasomotor symptoms and represents the commercial validation of nanoparticle technology for transdermal delivery of estrogen therapy (ET) for postmenopausal women with vasomotor symptoms.     

HRT and osteoporosis.

Osteoporosis is characterised by low bone mass, leading to an increased risk of fragility fracture, particularly in the femoral neck, vertebrae and radius. These fractures constitute a major public health problem in the Western world; the estimated annual cost to the health services of hip fracture alone is over 500 million pounds in the United Kingdom. Using population-based data from the USA, Cummings et al. have estimated that the lifetime risks of hip, vertebral and Colles' fractures in a 50 year old, white, postmenopausal woman are 16%, 32% and 15% respectively. Of these, vertebral fractures probably cause the most significant morbidity, since they occur at a younger age than hip fractures and may result in pain, deformity and disability for many years until death intervenes from other causes. Hip fractures occur most commonly in the eight and ninth decades of life and have a mortality at six months of around 15%, increased dependency occurring in the majority of survivors. Colles' fractures, although not usually associated with long-term morbidity, nevertheless cause considerable inconvenience and require hospital treatment.     

HRT: developments in therapy.

Various forms of oestrogen have been available for use as Hormone Replacement Therapy (HRT) for approximately 50 years. However, there has been little change in the mode of administration until the last 10-15 years. Although the oral route has remained the mainstay of therapy, non-oral routes of administration have been developed. During the 1970s it became clear that use of unopposed oestrogens in women with an intact uterus resulted in an increase in risk of endometrial carcinoma and thus the current practice of adding a sequential progestogen each month, to prevent endometrial hyperplasia, was introduced. However, certain progestogens can cause side-effects and some of the metabolic changes which they induce are potentially undesirable. Thus the search continues for new oral progestogens which are more 'metabolically friendly' than those in current use. Additionally, non-oral delivery systems for progestogens have been studied, such as the transdermal route (patches) and local administration within the uterine cavity (progestogen-containing intra-uterine devices). Both these strategies may minimise their symptomatic, psychological and metabolic effects. Continuous (every day) administration of progestogens in combination with the oestrogen, or the use of new compounds (e.g. tibolone) may overcome the problem of regular withdrawal bleeding which some women find unacceptable. However, it remains to be determined whether such therapies are as efficacious as conventional oestrogen/sequential progesterone regimens.