1 / 38

CHAPTER 14 Antiparkinsonian Drugs

CHAPTER 14 Antiparkinsonian Drugs. Parkinson’s Disease (PD). Chronic, progressive, degenerative disorder Affects the dopamine-producing neurons in the brain Caused by an imbalance of two neurotransmitters Dopamine Acetylcholine (ACh). Parkinson’s Disease (cont’d).

jody
Download Presentation

CHAPTER 14 Antiparkinsonian Drugs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAPTER 14Antiparkinsonian Drugs

  2. Parkinson’s Disease (PD) • Chronic, progressive, degenerative disorder • Affects the dopamine-producing neurons in the brain • Caused by an imbalance of two neurotransmitters • Dopamine • Acetylcholine (ACh)

  3. Parkinson’s Disease (cont’d) • Symptoms occur when about 80% of the dopamine stored in the substantia nigra of the basal ganglia is depleted • As long as there are functioning nerve terminals that can take up dopamine, symptoms can be partially controlled

  4. Parkinson’s Disease (cont’d) • PD is a progressive condition • Rapid swings in response to levodopa occur (“on-off phenomenon”) • PD worsens when too little dopamine is present • Dyskinesia occurs when too much is present

  5. Dyskinesia • Difficulty in performing voluntary movements • Two common types • Chorea: irregular, spasmodic, involuntary movements of the limbs or facial muscles • Dystonia: abnormal muscle tone leading to impaired or abnormal movements

  6. Levodopa Therapy • Levodopa is a precursor of dopamine • Blood-brain barrier does not allow exogenously supplied dopamine to enter, but does allow levodopa

  7. Levodopa Therapy (cont’d) • Levodopa is taken up by the dopaminergic terminal, converted into dopamine, then released as needed • As a result, the neurotransmitter imbalance is controlled in patients with early PD who still have functioning nerve terminals

  8. Levodopa Therapy (cont’d) • As PD progresses, it becomes more and more difficult to control it with levodopa • Ultimately, levodopa no longer controls the PD, and patient is seriously debilitated • This generally occurs between 5 and 10 years after the start of levodopa therapy

  9. Drug Therapy for PD • Aimed at increasing levels of dopamine as long as there are functioning nerve terminals remaining • Antagonizes or blocks the effects of ACh • Slows the progression of the disease

  10. Drug Therapy for PD (cont’d) • Anticholinergic drugs • benztropine, biperiden, others • Antihistamines • diphenhydramine, others • Dopamine-receptor agonists (direct acting) • bromocriptine, levodopa, pergolide, levodopa-carbidopa, others

  11. Drug Therapy for PD (cont’d) • Indirect-acting dopamine-receptor agonists • MAO-B inhibitor: selegiline • COMT inhibitor: entacapone, tolcapone • Miscellaneous drug: amantadine

  12. Selective Monoamine Oxidase Inhibitor (MAOI) Therapy • Selegiline is a newer, potent, irreversible MAOI that selectively inhibits MAO-B • Does not elicit the “cheese effect” of the nonselective MAOIs used to treat depression (if 10 mg or less is used)

  13. Selective MAOI Therapy: Selegiline • MAOIs break down catecholamines in the CNS, primarily the brain • Selegiline is a selective MAO-B inhibitor; it causes an increase in the levels of dopaminergic stimulation in the CNS

  14. Selective MAOI Therapy: Selegiline (cont’d) • Used in combination with levodopa or levodopa-carbidopa • Used as an adjunctive when a patient’s response to levodopa is fluctuating • Allows the dose of levodopa to be decreased; delays the development of unresponsiveness to levodopa therapy

  15. Selective MAOI Therapy: Selegiline (cont’d) • Improvement in functional ability • Decreased severity of symptoms • Only 50% to 60% of patients show a positive response to therapy • Prophylactic selegiline may delay the development of serious debilitating PD for 9 to 18 years

  16. Selective MAOI Therapy: Selegiline (cont’d) • Adverse effects usually mild • Nausea, lightheadedness, dizziness, abdominal pain, insomnia, confusion, dry mouth • Doses higher than 10 mg/day may cause more severe adverse effects, such as hypertensive crisis

  17. Dopaminergic Therapy • Used to provide exogenous replacement of lost dopamine or to enhance the function of the few neurons that are still producing their own dopamine • Goal: to increase levels of dopamine in the brain and reduce the most detrimental complications of PD

  18. Dopaminergic Therapy (cont’d) • Three categories • Replacement • Direct acting/replacement • Indirect acting

  19. Dopaminergic Therapy (cont’d) • Replacement drugs (presynaptic) • Work presynaptically to increase brain levels of dopamine • Levodopa is able to cross the blood-brain barrier, then is converted to dopamine • However, the large doses of levodopa needed to get dopamine to the brain also cause adverse effects

  20. Dopaminergic Therapy (cont’d) • Replacement drugs (presynaptic) (cont'd) • Carbidopa is given with levodopa • Carbidopa does not cross the blood-brain barrier, and prevents levodopa breakdown in the periphery • As a result, more levodopa crosses the blood-brain barrier, where it can be converted to dopamine

  21. Dopaminergic Therapy (cont’d) • Indirect acting: amantadine (Symmetrel) • Causes release of dopamine from the storage sites at the end of nerve cells that are still intact • Also blocks the reuptake of dopamine into the nerve endings, allowing more to accumulate both centrally and peripherally • Does not stimulate dopamine receptors directly

  22. Dopaminergic Therapy (cont’d) • ropinirole (Requip) • Newer, nonergot dopamine agonist • Used for PD, and restless leg syndrome

  23. Dopaminergic Therapy:Indications • Used to increase dopamine levels in the brain and reduce the severity of PD symptoms • Amantadine also has antiviral effects

  24. Anticholinergic Therapy • Anticholinergics block the effects of ACh • Used to treat muscle tremors and muscle rigidity associated with PD • These two symptoms are caused by excessive cholinergic activity • They do not relieve bradykinesia (extremely slow movements)

  25. Anticholinergic Therapy (cont’d) • ACh accumulates because of the imbalance of dopamine • As a result, overstimulation of the cholinergic excitatory pathways occurs • Muscle tremors and muscle rigidity • Cogwheel rigidity • Pill-rolling movement of fingers and head bobbing while at rest

  26. Anticholinergic Drugs Used for PD • benztropine mesylate (Cogentin) • trihexyphenidyl (Artane) • biperiden (Akineton) • procyclidine (Kemadrin)

  27. Anticholinergic Therapy:Indications • Used in the treatment of PD to cause smooth muscle to relax, resulting in reduced muscle rigidity and akinesia • Also used to treat drug-induced extrapyramidal reactions to certain antipsychotic drugs

  28. Anticholinergic Therapy:Adverse Effects • Drowsiness, confusion, disorientation • Constipation, nausea, vomiting • Urinary retention, pain on urination • Blurred vision, dilated pupils, photophobia, dry skin • Decreased salivation, dry mouth

  29. Nursing Implications • Perform a thorough assessment, nursing history, and medication history • Include questions about the patient’s: • CNS • GI and GU tracts • Psychologic and emotional status

  30. Nursing Implications (cont’d) • Assess for signs and symptoms of PD • Mask-like expression • Speech problems • Dysphagia • Rigidity of arms, legs, and neck • Assess for conditions that may be contraindications

  31. Nursing Implications (cont’d) • Administer drugs as directed by manufacturer • Provide patient education regarding PD and the medication therapy • Inform patient not to take other medications with PD drugs unless he or she checks with physician

  32. Nursing Implications (cont’d) • When starting dopaminergic drugs, assist patient with walking because dizziness may occur • Oral doses should be given to minimize GI upset • Encourage patient to force fluids to at least 2000 mL/day (unless contraindicated)

  33. Nursing Implications (cont’d) • Pyridoxine (vitamin B6) in doses greater than 10 mg will reverse the effects of levodopa • Teach patient to avoid foods high in vitamin B6 • Taking levodopa with MAOIs may result in hypertensive crisis

  34. Nursing Implications (cont’d) • Patients should be told not to discontinue antiparkinsonian drugs suddenly • Teach patients about what therapeutic and adverse effects to expect with antiparkinsonian drug therapy

  35. Nursing Implications (cont’d) • Levodopa preparations may darken the patient’s urine and sweat • Therapeutic effects may take weeks with other drugs • “Drug holidays”

  36. Nursing Implications (cont’d) • Monitor for response to drug therapy • Improved sense of well-being and mental status • Increased appetite • Increased ability to perform ADLs, to concentrate, and to think clearly • Less intense parkinsonian manifestations, such as less tremor, shuffling gait, muscle rigidity, and involuntary movements

More Related