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Pharmacology

Class II Beta Blockers 

Block SNS stimulation of beta receptors in the heart and decreasing risks of ventricular fibrillation
– Blockage of SA and ectopic pacemakers: decreases automaticity 
– Blockage of AV increases the refractory period
- Increase AV nodal conduction ´ 
- Increase PR interval
- Reduce adrenergic activity

Treatment: Supraventricular tachycardia (AF, flutter, paroxysmal supraventricular tachycardia 
– Acebutolol 
– Esmolol 
– Propanolol 

Contraindications and Cautions 

• Contraindicated in sinus bradycardia P < 45
• Cardiogenic shock,  asthma or respiratory depression which could be made worse by the blocking of Beta receptors. 
• Use cautiously in patients with diabetes and thyroid dysfunction, which could be altered by the blockade of Beta receptors 
• Renal and hepatic dysfunction could alter the metabolism and excretion of these drugs.
 

Itraconazole:

The drug may be given orally or intravenously.

Mixed Narcotic Agonists/Antagonists

These drugs all produce analgesia, but have a lower potential for abuse and do not produce as much respiratory depression.

A. Pentazocine

  • Has a combination of opiate analgesic and antagonist activity.
  • Orally, it has about the same analgesic potency as codeine.
  • In contrast to morphine, cardiac workload tends to increase due to an increase in pulmonary arterial and cerebrovascular pressure. Blood pressure and heart rate both also tend to increase.
  • Adverse reactions to Pentazocine

• Nausea, vomiting, dizziness.

• Psychotomimetic effects, such as dysphoria, nightmares and visual hallucinations.

• Constipation is less marked than with morphine.

B. Nalbuphine

  • Has both analgesic and antagonist properties.
  • Resembles pentazocine pharmacologically.
  • Analgesic potency approximately the same as morphine.
  • Appears to be less hypotensive than morphine.
  • Respiratory depression similar to morphine, but appears to peak-out at higher doses and to reach a ceiling.
  • Like morphine, nalbuphine reduces myocardial oxygen demand. May be of value following acute myocardial infarction due to both its analgesic properties and reduced myocardial oxygen demand.
  • Most frequent side effect is sedation.

C. Butorphanol

  • Has both opiate agonist and antagonist properties.Resembles pentazocine , pharmacologically., 3.5 to 7 times more potent than morphine., Produces respiratory depression, but this effect peaks out with higher doses. The respiratory depression that does occur lasts longer than that seen following morphine administration.
  • Butorphanol, like pentazocine, increases pulmonary arterial pressure and possibly the workload on the heart.
  • Adverse reactions include sedation, nausea and sweating.

D. Buprenorphine

  • A derivative of eto`rphine. Has both agonist and antagonist activity. 20 to 30 times more potent than morphine.Duration of action only slightly longer than morphine, but respiratory depression and miosis persist well after analgesia has disappeared.
  • Respiratory depression reaches a ceiling at relatively low doses.
  • Approximately 96% of the circulating drug is bound to plasma proteins.
  • Side effects are similar to other opiates:
    • sedation, nausea, vomiting,
    • dizziness, sweating and headache.

Acid-Peptic disorders

This group of diseases include peptic ulcer, gastroesophageal reflux and Zollinger-Ellison syndrome.

Pathophysiology of acid-peptic disorders

Peptic ulcer disease is thought to result from an imbalance between cell– destructive effects of hydrochloric acid and pepsin on the one side, and cell-protective effects of mucus and bicarbonate on the other side. Pepsin is a proteolytic enzyme activated in gastric acid (above pH of 4, pepsin is inactive); also it can digest the stomach wall. A bacterium, Helicobacter pylori, is now accepted to be involved in the pathogenesis of peptic ulcer.

In gastroesophageal reflux the acidic contents of the stomach enter into the oesophagus causing a burning sensation in the region of the heart; hence the common name heartburn or other names such as indigestion and dyspepsia.

However, Zollinger-Ellison syndrome is caused by a tumor of gastrin secreting cells of the pancreas characterized by excessive secretion of gastrin that stimulates gastric acid secretion.

These disorders can be treated by the following classes of drugs:

A. Gastric acid neutralizers (antacids)
B. Gastric acid secretion inhibitors (antisecretory drugs)
C. Mucosal protective agents
D. Drugs that exert antimicrobial action against H.pylori

Third Generation Cephalosporins 

Prototype drugs are CEFOTAXIME (IV) and CEFIXIME (oral). CEFTAZIDIME (for Pseudomonas aeruginosa.).

Further expansion of Gm negative spectrum to include hard to treat organisms such as Enterobacter, Serratia, and Pseudomonas. 
In addition to better Gm negative spectrum, this group has improved pharmacokinetic properties (longer half-lives) that allow once daily dosing with some agents. In general, activity toward Gm + bacteria is reduced. These are specialty antibiotics that should be reserved for specific uses. 

Enterobacteriaciae that are almost always sensitive (>95% sensitive)
E. coli
Proteus mirabilis (indole –)
Proteus vulgaris (indole +)
Klebsiella pneumoniae

Gram negative bacilli that are generally sensitive (>75% sensitive)
Morganella morganii
Providencia retgerri
Citrobacter freundii
Serratia marcescens
Pseudomonas aeruginosa (Ceftazidime only)


Gram negative bacilli that are sometimes sensitive (<75% sensitive)
Enterobacter
Stenotrophomonas (Xanthomonas) maltophilia (Cefoperazone & Ceftazidime only)
Acinetobacter

--> cefepime & cefpirome are promising for these bacteria

Bacteria that are resistant
Listeria monocytogenes
Pseudomonas cepacia
Enterococcus sp. 

Uses
1. Gram negative septicemia & other serious Gm – infections
2. Pseudomonas aeruginosa infections (Ceftazidime - 90% effective)
3. Gram negative meningitis - Cefotaxime, Ceftriaxone, Cefepime. For empiric therapy add vancomycin ± rifampin to cover resistant Strep. pneumoniae
4. Gonorrhea - Single shot of Ceftriaxone is drug of choice. Oral cefixime and ceftibuten are also OK.
5. Complicated urinary tract infections, pyelonephritis
6. Osteomyelitis - Ceftriaxone in home health care situations
7. Lyme disease - ceftriaxone in home health care situations

Meperidine (Demerol)

Meperidine is a phenylpiperidine and has a number of congeners. It is mostly effective in the CNS and bowel

  • Produces analgesia, sedation, euphoria and respiratory depression.
  • Less potent than morphine, 80-100 mg meperidine equals 10 mg morphine.
  • Shorter duration of action than morphine (2-4 hrs).
  • Meperidine has greater excitatory activity than does morphine and toxicity may lead to convulsions.
  • Meperidine appears to have some atropine-like activity.
  • Does not constrict the pupils to the same extent as morphine.
  • Does not cause as much constipation as morphine.
  • Spasmogenic effect on GI and biliary tract smooth muscle is less pronounced than that produced by morphine.
  • Not an effective antitussive agent.
  • In contrast to morphine, meperidine increases the force of oxytocin-induced contractions of the uterus.
  • Often the drug of choice during delivery due to its lack of inhibitory effect on uterine contractions and its relatively short duration of action.
  • It has serotonergic activity when combined with monoamine oxidase inhibitors, which can produce serotonin toxicity (clonus, hyperreflexia, hyperthermia, and agitation)

 

 Adverse reactions to Meperidine

• Generally resemble a combination of opiate and atropine-like effects.

- respiratory depression, - tremors, - delirium and possible convulsions, - dry mouth

• The presentation of mixed symptoms (stupor and convulsions) is quite common in addicts taking large doses of meperidine.

Class I Sodium Channel Blockers 

• Block movement of sodium into cells of the cardiac conducting system
• Results in a stabilizing effect and decreased formation and conduction of electrical impulses 
• Have a local anesthetic effect
• Are declining in use due to proarrhythmic effects and increased mortality rates 

• Na channel blockers - Class 1 drugs are divided into 3 subgroups 
• 1A. 1B, 1C based on subtle differences in their mechanism of action. 
• Blockade of these channels will prevent depolarization. 
• Spread of action potential across myocardium will slow and areas of  pacemaker activity is suppressed.

Class IA Sodium Channel Blockers 

• Treatment of: symptomatic premature ventricular contractions, supraventricular tachycardia, and ventricular tachycardia, prevention of ventricular fibrillation
– Quinidine (Cardioquin, Quinaglute) 
– Procainamide (Pronestyl, Procanbid) 
– Disopyramide (Norpace) 

• Quinidine – prototype 
• Low therapeutic index
• High incidence of adverse effects 

Class IB Sodium Channel Blockers 

• Treatment of: symptomatic premature ventricular contractions and ventricular tachycardia, prevention of ventricular  fibrillation
– Lidocaine (Xylocaine) 
– Mexiletine (Mexitil) 
– Tocainide (Tonocard) 
– Phenytoin (Dilantin) 

Side Effects: Lidocaine 
• Drowsiness • Paresthesias  • Muscle twitching • Convulsions  • Changes in mental status (disorientation, confusion) • Hypersensitivity reactions (edema, uticaria, anaphylaxis) 

Side Effects: Phenytoin (Dilantin)
• Gingival hyperplasia 
• Nystagmus 
• Ataxia, slurring of speech 
• Tremors 
• Drowsiness 
• Confusion 

• Lidocaine – prototype 
• Must be given by injection 
• Used as a local anesthetic 
• Drug of choice for treating serious ventricular arrhythmias associated with acute myocardial infarction, cardiac surgery, cardiac catheterization and electrical conversion 

Class IC Sodium Channel Blockers
• Treatment of: life-threatening ventricular tachycardia or fibrillation and supraventricular tachycardia unresponsive to other  drugs 

– Flecainide 
– Propafenone 

Adverse Effects 
• CNS - dizziness, drowsiness, fatigue, twitching, mouth numbness, slurred speech vision changes, and tremors that can progress to convulsions.
• GI - changes in taste, nausea, and vomiting. CV - arrhythmias including heart blocks, hypotension, vasodilation, and potential for cardiac arrest. 
• Other Rash, hypersensitivity reactions loss of hair and potential bone marrow depression. 

Drug-Drug Interactions
• Increased risk for arrhythmias if combined with other drugs that are know to cause arrhythmias- digoxin and beta blockers 
• Increased risk of bleeding if combined with oral anticoagulants. 

Drug Food Interactions
• Quinidine needs an acidic urine for excretion. Increased levels lead to toxicity 
• Avoid foods that alkalinize the urine- citrus juices, vegetables, antacid, milk products

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