NEET MDS Lessons
Pharmacology
Chloral hydrate
1. Short-acting sleep inducer—less risk of “hangover” effect the next day.
2. Little change on REM sleep.
3. Metabolized to trichloroethanol, an active metabolite; further metabolism inactivates the drug.
4. Used for conscious sedation in dentistry.
5. Can result in serious toxicity if the dose is not controlled.
Megltinides
nateglinide
repaglinide
Mechanism
binds to K+ channels on β-cells → postprandial insulin release
Clinical use
type 2 diabetes mellitus
may be used as monotherapy, or in combination with metformin
NSAIDs: Classification by Plasma Elimination Half Lives
Short Half Life (< 6 hours):
more rapid effect and clearance
• Aspirin (0.25-0.33 hrs),
• Diclofenac (1.1 ± 0.2 hrs)
• Ketoprofen (1.8± 0.4 hrs),
• Ibuprofen (2.1 ± 0.3 hrs)
• Indomethacin (4.6 ± 0.7 hrs)
Long Half Life (> 10 hours):
slower onset of effect and slower clearance
• Naproxen (14 ± 2 hrs)
• Sulindac (14 ± 8 hrs),
• Piroxicam (57 ± 22 hrs)
Carbamazepine (Tegretol): most common; for generalized tonic-clonic and all partial seizures; especially active in temporal lobe epilepsies
Mechanism: ↓ reactivation of Na channels (↑ refractory period, blocks high frequency cell firing, ↓ seizure spread)
Side effects: induces hepatic microsomal enzymes (can enhance metabolism of other drugs)
Nystatin
Candida spp. are sensitive to nystatin.
Uses: Cutaneous, vaginal, mucosal and esophageal infections.
Candida infections can be treated with nystatin.
Cryptococcus is also sensitive to nystatin.
Nystatin is often used as prophylaxis in patients who are at risk for fungal infections, such as AIDS patients with a low CD4+ count and patients receiving chemotherapy.
MOA
nystatin binds to ergosterol, the main component of the fungal cell membrane. When present in sufficient concentrations, it forms a pore in the membrane that leads to K+ leakage and death of the fungus.
PSEUDOEPHEDRINE
Pseudoephedrine appears to have less pressor activity and weaker central nervous system effects than ephedrine. It has agonist activity at both β1 and β2 adrenoceptors, leading to increased cardiac output and relaxation of bronchial smooth muscle.
Pseudoephedrine is rapidly absorbed throughout the body. It is eliminated largely unchanged in urine by N-demethylation.
It is indicated in symptomatic relief from stuffed nose, respiratory tract congestion, bronchospasm associated with asthma, bronchitis and other similar disorders.
Dextromethorphan
O-methylated dextrorphan, Excellent oral antitussive, No analgesic effect, No GI effects, No respiratory depression