NEET MDS Lessons
Pharmacology
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).
Kinins
Peptide that are mediated in the inflammation.
Action of kinin:
On CVS: vasodilatation in the kidneys, heart, intestine, skin, and liver. It is 10 times active than histamine as vasodilator.
On exocrine and endocrine glands: kinin modulate the tone of pancreas and salivery glands and help regulate GIT motility, also affect the transport of water and electrolytes, glucose and amino acids through epithelial cell transport.
Tetracycline
Tetracycline is an antibiotic produced by the streptomyces bacterium
Mechanism and Resistance Tetracycline inhibits cell growth by inhibiting translation. It binds to the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. This prevents the addition of amino acids to the elongating peptide chain, preventing synthesis of proteins. The binding is reversible in nature.
Example: Chlortetracycline, oxytetracycline, demethylchlortetracycline, rolitetracycline, limecycline, clomocycline, methacycline, doxycycline, minocycline
Source: Streptomyces spp.; some are also semi-synthetic
Spectrum of activity: Broad-spectrum. Exhibits activity against a wide range of Gram-positive, Gram-negative bacteria, atypical organisms such as chlamydiae, mycoplasmas, rickettsiae and protozoan parasites.
Effect on bacteria: Bacteriostatic
Cells become resistant to tetracyline by at least two mechanisms: efflux and ribosomal protection.
Contraindications Tetracycline use should be avoided during pregnancy and in the very young (less than 6 years) because it will result in permanent staining of teeth causing an unsightly cosmetic result.
Tetracyclines also become dangerous past their expiration dates. While most prescription drugs lose potency after their expiration dates, tetracyclines are known to become toxic over time; expired tetracyclines can cause serious damage to the kidneys.
Miscellaneous: Tetracyclines have also been used for non-antibacterial purposes, having shown properties such as anti-inflammatory activity, immunosuppresion, inhibition of lipase and collagenase activity, and wound healing.
Other sedatives: carisoprodol, cyclobenzaprine, and methocarbamol are used for muscle relaxation.
Baclofen
1. Used in spasticity states to relax skeletal muscle.
2. Occasionally used in trigeminal neuralgia.
Antihistamines (first-generation H1 receptor blockers)
1. Used for sedation (e.g., diphenhydramine).
Ethyl alcohol
Specific Agents
Hydralazine [orally effective]
MOA: Not completely understood. Seems to be partially dependent on the release of EDRF and perhaps partially due to K+-channel activation
- in clinical doses action is manifest primarily on vascular smooth muscle (non-vascular muscle is not much affected).
- Re: Metabolism & Excretion. In cases of renal failure the plasma half life may be substantially increased (4-5 fold). One mode of metabolism is
via N-Acetylation (problem of slow acetylators)
Side Effects
- those typical of vasodilation = headache, nasal congestion, tachycardia etc.
- chronic treatment with high doses > 200 mg/day may induce a rheumatoid-like state which may resemble lupus erythematosus.
Minoxidil (Loniten) [orally effective]
MOA: K+-channel agonist
- very effective antihypertensive. Used primarily to treat life-threatening hypertension or hypertension resistant to other agents.
Side effects - growth of hair
Diazoxide (Hyperstat) [used only IV]
MOA: K+-channel agonist
- Administered by rapid IV injection; action appearing after 3-5 min; action may last from 4 to 12 hours.
Nitroprusside (Nipride) [used only IV]
MOA: increase in cGMP
- unlike the other vasodilators, venous tone is substantially reduced by nitroprusside.
- rapid onset of action (.30 sec); administered as an IV-infusion.
- particularly useful for hypertension associated with left ventricular failure.
Etomidate -Intravenous Anesthetics
- A nonbarbiturate anesthetic used primarily to induce surgical anesthesia.
- It does not produce analgesia.
- Etomidate has minimal effect on the cardiovascular system and respiration during induction of anesthesia.
- Like the barbiturates, etomidate decreases cerebral blood flow, cerebral metabolic rate and intracranial pressure.
- No changes in hepatic, renal or hematologic function have been reported.
- Myoclonic muscle movements are relatively common.
- Postoperative nausea and vomiting are more common with etomidate than with barbiturates.
Glitazones (thiazolidinediones)
Thiazolidinediones, also known as the "-glitazones"
pioglitazone
rosiglitazone
Mechanism
bind to nuclear receptors involved in transcription of genes mediating insulin sensitivity
peroxisome proliferator-activating receptors (PPARs)
↑ insulin sensitivity in peripheral tissue
↓ gluconeogenesis
↑ insulin receptor numbers
↓ triglycerides
Clinical use
type II DM
as monotherapy or in combination with other agents
contraindicated in CHF
associated with increased risk of MI (in particular rosiglitazone)