Central Nervous System Drugs: Pharmacology and Nursing Implications

1. Pharmacology Spring 09 – Unit 2 Carla Hilton, MSN, RN, CNE Lecture 3 Chapters 28, 77

2. Learning Outcomes • Compare and contrast fundamental concepts related to the use of specific central nervous system drugs, including those used for management of pain, drugs related to the maintenance of bowel function and the management of constipation. • Acquire a working framework for studying drug classifications and nursing implications.

3. Classifications:Opioid (Narcotic) Analgesics, Opioid Antagonists, and Non-opioid Centrally Acting Analgesics Chapter 28

4. Intro to Opioids • Chemical class: Opioid vs opiate • Opiod means they act like an opiate • Opiates are from poppy seeds • Functional class: Narcotic Analagesic • MOA – body peptides (3) enkephalins, endorphins, dynorphins (they produce their effects at these receptor sites) • Opioid receptors - mu, kappa, and delta • Agonist, partial agonist, antagonist • Partial agonists produces low to moderate activation alone, but will block actions of full agonists if given simultaneously • Strong and moderate to strong

5. Table 28-1

6. Opioid Agonists • Prototypes • Strong: morphine [Duramorph] CII • Moderate to strong: codeine [Paveral] CIII • MOA / TE • Mimics action of endogenous opioid receptors (mu) to produce analgesia and thereby relieve pain • Other effects include drowsiness, mental clouding, anxiety reduction, sense of well-being. CNS Depressant • Oral dose is a lot higher than IV in this case

7. Adverse Effects • Resp. depression • Diminished by “tolerance” • Most common cause of OD death • Others • Constipation, orthostatic hypotension, urinary retention / urgency, cough suppression, biliary colic, emesis, elevated ICP (intracranial pressure), dysphoria, sedation, miosis (small pupils), neurotixicity, immune and hormone suppression with prolonged use • Toxicity • Classic triad (coma, resp. depression, pinpoint pupils)

8. Miosis- tiny little pin point pupils Mydriasis- with the d in the word, think dilated pupils

9. ADME (Pharmacokinetics) Nursing implications? • Given by several routes • Slowest to fastest • Time-frame for TE varies by mode of administration • If you want the drug now, do IV. We need to know how long it takes these to work • Denatured in liver • Hard to cross blood-brain barrier • Precautions / Contraindications • Decreased resp reserve, pregnancy, head injury, infants (crosses placenta) / elderly, hypotension, liver disease • Interactions • CNS depressants, antihistamines, antihypertensives, MOAIs*, antiemetics, amphetamines, agonist-antagonist, antagonists

10. Dosage – Highly individualized • Table 28-6 • Administration • po, IM, IV, SQ, topical, PCA • Oral associated with chronic • Preferably fixed schedule • Site specific – hazards (epidural, effects delayed…)

11. Other Strong Opioids • Fentanyl (Sublimaze) • Anesthesia primary use (injectable) • 100 X mg potency of morphine • Commonly seen as transdermal • No children under 2 / none for under 18 less than 100 lbs. • Transmucosal (popsicle) • Breakthrough cancer pain • Store carefully • very large amts of drug (can kill!)

12. Meperidine [Demerol] • Interacts with several drugs – esp MAOI’s • Toxic metabolite (had problems in the elderly) • Avoid use past 48 hrs and not to exceed 600mg/24hr. • Hydromorphone [Dilaudid] • Methadone • Help people addicted to heroin • Heroin – crosses blood-brain easier

13. Table 28-6 – Dosing for Opioids

14. Moderate to Strong Opioid Agonists • Codeine • Usual dose of 30 mg = about same relief as 325 mg of ASA or Tylenol • Combo meds more effective • Extremely effective cough suppressant at 10 mg dose range • Oxycodone [OxyContin, Percodan] & CR forms • Hydrocodone [Lortab, Norco, Vicodin] CIII • Proproxyphene [Darvon, Darvocet] CIV

15. Special Clinical Concepts r/t Use of Opioids • Pain assessment – including evaluation! • Dosing amt and schedule • Fear of addiction in clinical setting • Avoiding withdrawal – 20 days or more • They can have withdrawal symptoms • Patient controlled anesthesia (PCA) • Morphine: DOC - heart attack (MI) • Meperidine [Demerol]: DOC OB • Doesn’t cross placenta • Avoid opioids in Head Injury…

16. Nursing Implications • Link to ATI pp. 133 (150)

17. Class: Opioid Agonist-Antagonists • Prototype: pentazocine [Talwin] • Others: nalbuphine [Nubain], butorphanol [Stadol] • MOA - act mostly at mu kappa receptor to produce analgesia and relieve pain. • Alone = agonist action • With agonist = can antagonize (blocks mu receptor) • Adverse effects – similar to opioids • ADME (Pharmacokinetics) • Less respiratory depression, low abuse potential • Less effective pain relief • *Can start withdrawal sxms in opioid addiction

18. Class: Opioid Antagonists • Prototype: naloxone [Narcan] • MOA – TE / Use • competes for opiate site and blocks effects of opioid agonists / agonist-antagonists – no significant effect given alone – resulting in REVERSAL of narcotic • ADME • Rebound effect (narcan wears off and they are back under the morphine…) • Adverse effects: acute withdrawal • Dosage/Admin: 04. mg IM, IV, SubQ • Others: naltrexone [ReVia] ETOH/Opioid abuse

19. Non-opioid Centrally Acting Analgesics • Prototype: Tramadol [Ultram] • Others: clonidine [Duraclon] is another centrally acting analgesic – pain / HTN • MOA / TE / Use • Analog of codeine – binds w mu receptor producing analgesia to relieve pain. Also blocks re-uptake of norepinephrine (lots of this in your system) • ADME (Pharmacokinetics) • Minimal potential for dependence or resp depression • Adverse effects • Rare – most common: sedation, dizziness, HA, dry mouth, and constipation • Precautions • Can intensify other CNS dep. – ABSOLUTELY avoid MAOIs

20. Laxatives Chapter 77

21. Bulk-forming • Prototype(s): methylcellulose, psyllium (Metamucil) • Action / Use • Behave like dietary fiber – nonabsorbable – swell to form viscous solution / gel and softening fecal mass and increasing transit. • Temp relief of constipation, diarrhea, irritable bowel, ostomies • Adverse effects • Esophageal & intestinal obstruction if not enough fluid  ? If you don’t take with enough fluid you can obstruct stuff. Builds a brick in the gut that doesn’t move (If this, then?)

22. Surfactants • Prototype: docusate sodium (Colace) • Action / Uses • Lower surface tension of stool and softens by facilitating penetration of water into the feces • Act on intestinal wall to inhibit fluid absorption and stimulate secretion of water and electrolytes into the intestinal lumen. • Brings water into the stool and makes it softer • ADME • Full glass of water • Sit upright for 30 min (kind of oil based and you can aspirate the stuff and get pneumonia) • Effectiveness dose related (min 200 mg/day) • Adverse reactions – rare • Dosage: 50 to 500 mg daily ( but usually at least 200 mg a day)

23. StimulantsTypically abused the most • Prototype(s): bisacodyl (Dulcolax), senna (Senekot) • Action / Legitimate Uses • Directly stimulate gut motility, increase secretion of water and ions into intestine, and reduce water and electrolyte absorption. • Uses: Treatment of (1) opioid-induced constipation and (2) slow transit constipation • Dosage: related to formulation administered • Take bisacodyl no sooner than 1 hour after ingesting milk or antacids – do not crush • Adverse reactions • Bowel rupture can occur • If you have gut surgery and your sutures are healing, if you give them this is makes their gut move and can tear open the incision

24. Osmotics • Salts Prototype: sodium phosphate (Fleet) and magnesium salts • Action /Uses • Non-absorbable and retains water in the colon • Adverse reaction • Dehydration, diarrhea and loss of water (more with salts than with glycol) • Magnesium can accumulate to toxic levels in renal failure • Sodium can retain fluid – so…. Contraindicated in patients with heart failure HTN and edema • Other: glycol (MiraLax) – fewer side effects / safer

25. Miscellaneous • Lactulose (sugar base) • Action / Uses • Poorly absorbed and cannot be digested – by product of breakdown results in osmotic diuresis • Enhances excretion of ammonia in liver failure • SEs – flatulence, cramping • Glycerin Suppository • Polyethylene Glycol-Electrolyte (GoLytely) • Safe in dehydrated or electrolyte sensitive

26. Additional Nursing Implications • High risk patients • Contraindicated in abdominal pain, nausea, cramps, regional enteritis, diverticulitis, ulcerative colitis, acute surgical abdomen, fecal impaction, bowel obstruction. • Abuse • Castor oil (powerful stimulant – avoid at night – not to children)