As people grow old, their need for medications increases dramatically because of the higher incidence of
chronic pain,
diabetes mellitus, cardiovascular and neurological diseases in the elderly population. Furthermore, the elderly require special consideration with respect to
drug delivery, drug interactions and adherence. In particular, patients with chronic neurological diseases often require multiple administration of drugs during the day to maintain constant plasma medication levels, which in turn increases the likelihood of poor adherence. Consequently, several attempts have been made to develop pharmacological preparations that can achieve a constant rate of
drug delivery. For example, transdermal
lisuride and
apomorphine have been shown to reduce motor fluctuations and duration of 'off' periods in advanced
Parkinson's disease, while
rotigotine allows significant down-titration of
levodopa without severe adverse effects. Thus, parkinsonian patients with long-term
levodopa syndrome or
motor disorders during sleep could benefit from use of transdermal
lisuride and
apomorphine. Moreover, transdermal
dopaminergic drugs, particularly
rotigotine, seem the ideal treatment for patients experiencing
restless legs syndrome or
periodic limb movement disorder during
sleep, disorders that are quite common in elderly people or in association with
neurodegenerative diseases. Unlike
dopaminergic drugs, transdermal treatments for the management of cognitive and behavioural dysfunction in patients with
Parkinson's disease and
Alzheimer's disease have inconsistent effects and no clearly established role. Nevertheless, because of their favourable pharmacological profile and bioavailability, the
cholinesterase inhibitors tacrine and
rivastigmine are expected to show at least the same benefits as oral formulations of these drugs, but with fewer severe adverse effects. Transdermal delivery systems play an important role in the management of
neuropathic pain. The transdermal
lidocaine (
lignocaine) patch is recommended as first-line
therapy for the treatment of
postherpetic neuralgia. Furthermore, in patients with severe persistent
pain, transdermal delivery systems using the
opioids fentanyl and
buprenorphine are able to achieve satisfactory
analgesia with good tolerability, comparable to the benefits seen with oral formulations.
Transdermal administration is the ideal therapeutic approach for chronic
neurological disorders in elderly people because it provides sustained therapeutic plasma levels of drugs, is simple to use, and may reduce systemic adverse effects. Several transdermal delivery systems are currently under investigation for the treatment of
Parkinson's disease,
Alzheimer's disease and
neuropathic pain. Although most transdermal delivery systems treatments cannot be considered as first-line
therapy at present, some of them provide clear advantages compared with other routes of administration and may become the preferred treatment in selected patients. In general, however, most transdermal treatments still require long-term evaluation in large patient groups in order to optimise dosages and evaluate the actual incidence of local and systemic adverse effects.