McKenna's Pharmacology for Nursing, 2e

374

P A R T 4  Drugs acting on the central and peripheral nervous systems

Treatment At this time, there is no treatment that arrests the neuron degeneration of Parkinson’s disease and the eventual decline in the person’s function. Surgical procedures involving the basal ganglia have been tried with varying success at prolonging the degeneration caused by this disease. Drug therapy remains the primary treatment. Therapy is aimed at restoring the balance between the declining levels of dopamine, which has an inhibit­ ory effect on the neurons in the basal ganglia, and the now-dominant cholinergic neurons, which are excitat­ ory. This may help to reduce the signs and symptoms of parkinsonism and restore normal function for a time (Figure 24.2). Total management of care in individuals with Parkin­ son’s disease presents a challenge. People should be encouraged to be as active as possible, to perform exer- cises to prevent the development of skeletal deformities and to attend to their care as long as they can. Both the person and their family need instruction about follow­ ing drug protocols and monitoring adverse effects, as well as encouragement and support for coping with the progressive nature of the disease (Box 24.1). Because of the degenerative effects of this disease, individuals may experience episodes of depression or emotional upset. Psychological support, as well as physical support, is a crucial aspect of care.

■■ The loss of dopamine-secreting cells results in a loss of the inhibitory dopamine effect and is thought to be responsible for Parkinson’s disease.

DOPAMINERGIC AGENTS Dopaminergics —drugs that increase the effects of dopamine at receptor sites—have been proven to be even more effective thananticholinergics in the treatment of par- kinsonism (see Table 24.1). Dopaminergic agents include amantadine ( Symmetrel ), apomorphine ( Apomine ), bromocriptine ( Parlodel ), cabergoline ( Bergoline ), carbidopa–levodopa ( Sinemet ), levodopa-benserazide ( Madopar ), levodopa-carbidopa-entacapone ( Stalevo ), pergolide ( Permax ), pramipexole ( Sifrol ), ropinirole ( Appese , Repreve ) and rotigotine ( Neupro ) (not available in New Zealand). Therapeutic actions and indications Dopamine does not cross the blood–brain barrier. Therefore, other drugs that act like dopamine or increase dopamine concentrations indirectly must be used to increase dopamine levels in the substantia nigra or to directly stimulate the dopamine receptors in that area. This action helps to restore the balance between the inhibitory and stimulating neurons. Dopaminergic agents are effective as long as enough intact neurons remain in the substantia nigra to respond to increased levels of dopamine. After the neural degeneration has progressed beyond a certain point, these agents are no longer effective. The dopaminergics are indicated for the relief of the signs and symptoms of idiopathic Parkinson’s disease

KEY POINTS

■■ Parkinson’s disease is a progressive nervous system disease characterised by tremors, changes in posture and gait and a mask-like facial expression.

INHIBITION

STIMULATION

Type 1 drugs

Basal ganglia cells

Type 2 drugs

A. Increase dopamine concentration levodopa B. Increases dopamine release amantadine rasagiline C. Stimulate dopamine receptors

Anticholinergic drugs block stimulant benztropine biperiden benzhexol

FIGURE 24.2  Drug therapy in treating Parkinson’s disease is aimed at achieving a balance between the stimulating cholinergic effects and the inhibitory effects of dopamine in the basal ganglia. Type 1 drugs affect dopamine and are inhibitory. Type 2 drugs block cholinergic effects, preventing stimulation.

apomorphine bromocriptine pramipexole ropinirole cabergoline

pergolide rotigotine