Pharmacology

Pharmacodynamics

• Pharmocodynamics is the science dealing with interactions between the chemical components of living systems and foreign chemicals, including drugs, that enter those systems.
• It examines how a drug affects living tissues within an organism.
• The actual concentration of a drug in the body results from a dynamic equilibrium involving several processes:
  • Absorption from the site of entry
  • Distribution to the active site
  • Biotransformation (metabolism) in the liver
  • Excretion from the body

Anxiolytics and Hypnotic Agents

• Barbiturates include:
  • Amobarbital (Amytal Sodium)
  • Pentobarbital (Nembutal)
  • Phenobarbital (Luminal)
  • Secobarbital (Seconal)
• Nursing contraindications:
  • Assess for baseline status before beginning therapy and for occurrence of any adverse effects
  • Do not mix IV drugs with any other drugs to avoid potential drug-drug interactions
  • Give parenteral forms only if oral forms are not feasible
  • Give IV medications slowly to avoid potential cardiac problems
  • Provide standby life-support facilities in case of severe respiratory or hypersensitivity reactions
  • Taper dose gradually to avoid precipitating seizures and withdrawal syndrome
  • Provide support measures

Pharmacotherapy of Glaucoma

• Selected drugs for glaucoma:
  • Prostaglandins
  • Beta-adrenergic blockers
  • Alpha2-adrenergic agonists
  • Carbonic anhydrase inhibitors
  • Cholinergic Agonists (Miotics)

Antidiarrheals and Opioids

• Mechanism of action: slows peristalsis, allowing for more fluid and electrolyte absorption
• Primary use: for moderate to severe diarrhea
• Drugs:
  • Diphenoxylate with atropine (Lomotil)
  • Codeine
  • Loperamide (Imodium)
  • Difenoxin +atropine (Motofen)
  • Camphorated opium tincture (Paregoric)
  • Bismuth salts
  • Lactobacillus acidophilus
  • Octreotide (Sandostatin)
• Side effects and nursing considerations:
  • Assess fluid and electrolyte status
  • Assess for blood in stool
  • Do not use if constipation should be avoided
  • Assess patient's ability to get out of bed safely
  • Antidiarrheals contraindicated in some patients, such as those with severe dehydration, electrolyte imbalance, liver, and renal disorders, and glaucoma

Irritable Bowel Syndrome (IBS)

• Also known as spastic colon or mucous colitis
• Common disorder of the lower gastrointestinal tract
• Symptoms:
  • Abdominal pain, bloating, excessive gas, and colicky cramping
  • Diarrhea alternating with constipation
  • Mucus in stool
• Causes:
  • Functional bowel disorder
• Treatment:
  • Supportive, symptomatic treatment
  • Lifestyle changes, including dietary changes and relaxation therapy
  • Altered bowel habits
  • Bulk laxatives, such as psyllium
  • Anticholinergic medications, such as dicyclomine (Bentyl)
  • Tegaserod

Cephalosporins

• Mechanism of action: inhibits bacterial cell wall synthesis
• 3rd generation:
  • Cefdinir, cefixime, cefotaxime, ceftazidime, ceftriaxone
  • Longer duration of action, resistant to beta-lactamase
  • Drug of choice for klebsiella, pseudomonas, Neisseria, salmonella, proteus, and H. influenza
• 4th and 5th generation:
  • Cefepime, ceftaroline
  • Effective against organisms that develop resistance to earlier cephalosporins
  • 4th generation: capable of entering CSF to treat CNS infections
  • 5th generation: effective against MRSA

Sulfonamides

• Mechanism of action: suppresses bacterial growth by inhibiting bacterial synthesis of folic acid (bacteriostatic)
• Wide spectrum against both gram-negative and gram-positive bacteria
• Also known as folic acid inhibitors
• Primary use: for urinary tract infections, Pneumocystis carinii pneumonia, and shigella infections of the small bowel
• Drugs:
  • Trimethoprim-sulfamethoxazole (Bactrim, Septra)
  • Sulfadiazine
• Side effects and nursing considerations:
  • Monitor for hypersensitivity to the drug
  • Monitor adverse effects
  • Monitor for agranulocytosis

Antitubercular Drugs

• Mechanism of action: inhibits bacterial growth and replication
• Multiple drug therapy is necessary because the Mycobacteria grow slowly, and resistance is common
• Using multiple drugs in different combinations during the long treatment period lowers the potential for resistance and increases the chances for successful therapy
• Precautions to avoid adverse effects are required, and the drugs will be required for a longer period than 1 month

Pain Management

• Nonpharmacologic techniques, such as relaxation techniques and guided imagery, can be used as an adjunct to medication for pain management
• Rationale: may allow for lower doses of drugs with fewer adverse effects