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Pharmacology - NEETMDS- courses
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Pharmacology

Beta-Adrenergic blocking Agents 

• Prototype - Propranolol 
• Prevent or inhibit sympathetic stimulation
– Reduces heart rate
– Myocardial contractility 
– Reduce BP - decreases myocardial workload and O2 demand 
• In long-term management used to decrease frequency and severity of anginal attacks 
• Added when nitrates do not prevent anginal episodes 
• Prevents exercise induced tachycardia
• Onset of action 30 min after oral dose. 1-2 min IV

Therapeutic Actions
• Block Beta adrenergic receptors in the heart and juxtaglomerular apparatus 
• Decrease the influence of the sympathetic nervous system decreasing excitability of the heart 
• Decrease cardiac output. 
• Indicated for long term management of anginal pectoris caused by atherosclerosis 

Atenolol, metoprolol, and nadolol have the same actions, uses, and adverse effects as propranolol, but they have long half-lives and can be given once daily. They are excreted by the kidneys, and dosage must be reduced in clients with renal impairment.

EPHEDRINE

It act indirectly and directly on α and β receptors. It increases blood pressure both by peripheral vasoconstriction and by increasing the cardiac output. Ephedrine also relaxes the bronchial smooth muscles.

Ephedrine stimulates CNS and produces restlessness, insomnia, anxiety and tremors.
Ephedrine produces mydriasis on local as well as systemic administration.
Ephedrine is useful for the treatment of chronic and moderate type of bronchial asthma, used as nasal decongestant and as a mydriatic without cycloplegia. It is also useful in preventing ventricular asystole in Stokes Adams syndrome.

SGLT-2 Inhibitors

canagliflozin
empagliflozin

Mechanism

glucose is reabsorbed in the proximal tubule of the nephron by the sodium-glucose cotransporter 2 (SGLT2)
SGLT2-inhibitors lower serum glucose by increasing urinary glucose excretion
the mechanism of action is independent of insulin secretion or action

Clinical use

type II DM

Benzodiazepines
All metabolites are active sedatives except the final glucuronide product. Elimination half-life varies a great deal from drug to drug.

?-Hydroxylation is a rapid route of metabolism that is unique to triazolam, midazolam, and alprazolam.
This accounts for the very rapid metabolism and short sedative actions of these drugs.

Pharmacological effects of benzodiazepines

- Antianxiety.
- Sedation.
- Anticonvulsant (including drug-induced convulsions).
- Amnesia, especially drugs like triazolam.
- Relax skeletal muscle (act on CNS polysynaptic pathways).

Indications

- IV sedation, (e.g., midazolam, diazepam, lorazepam).
- Antianxiety.
- Sleep induction.
- Anticonvulsant (e.g., diazepam, clonazepam).
- Panic disorders.
- Muscle relaxation.


Adverse effects

- Ataxia, confusion.
- Excessive sedation.
- Amnesia (not a desired effect with daytime sedation).
- Altered sleep patterns (increase stage 2 and decrease stage 4 sleep).

Diclofenac

Short half life (1‐2 hrs), high 1stpass metab.,  accumulates in synovial fluid after oral admn., reduce inflammation, such as in arthritis or acute injury

Mechanism of action

inhibition of prostaglandin synthesis by inhibition of cyclooxygenase (COX). There is some evidence that diclofenac inhibits the lipooxygenase pathways, thus reducing formation of the

leukotrienes (also pro-inflammatory autacoids). There is also speculation that diclofenac may inhibit phospholipase A2 as part of its mechanism of action. These additional actions may explain the high potency of diclofenac - it is the most potent NSAID on a molar basis.

Inhibition of COX also decreases prostaglandins in the epithelium of the stomach, making it more sensitive to corrosion by gastric acid. This is also the main side effect of diclofenac and other drugs that are not selective for the COX2-isoenzyme.

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.

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.

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