Ethinyl estradiol and norgestrel are a combination of drugs used as hormonal contraceptive in women. Ethinyl estradiol is synthetic estrogen analogue and norgestrel is a synthetic progesterone analogue.
Mechanism of action
Ethinyl estradiol and norgestrel cause feed back inhibition of GNRH (Gonadotropin releasing hormone), FSH (follicle stimulating hormone) and LH (leutinizing hormone). Thus the mid cycle LH surge is prevented and ovulation does not occur. Progesterone makes the cervical mucus thick and impenetrable to sperms. The tubal and uterine motility is affected in such a way as to prevent fertilisation. Even if ovulation and fertilization …

Linezolid is an oxazolidinone antimicrobial agent. It is a bacteriostatic agent.
Spectrum of action
MRSA (Methicillin resistant Staphylococcus areus), some VRSA (Vancomycin resistant Staphylococcus areus), VRE (Vancomycin resistant enterococci), Streptococcus pyogenes, S. viridans, S. pneumoniae, Clostridia, Mycobacterium tuberculosis, Listeria.
Mechanism of action
It binds to the 23S fraction of the 50S subunit of the bacterial ribosome. It prevents the formation of N-formyl methionine tRNA – 70S ribosome complex, thus preventing protein synthesis. Since the drug has a different site of action, it does not have cross resistance with other antimicrobial agents.
Pharmacokinetics
It is well absorbed orally.
Uses
Linezolid should …

Urinary antiseptics are antimicrobial agents. When these are given in orally tolerated doses, they attain antibacterial concentrations only in urine due to concentration in the renal tubules. These can be given for lower urinary tract infections, but are not suitable for upper urinary tract infections. eg: nitrofurantoin, methenamine.

Isoniazid is an antituberculous drug. It can cause peripheral neuropathy and rarely convulsions by decreasing the availability of pyridoxine (vitamin B6). Isoniazid binds to pyridoxal-5-phosphate, the active form of pyridoxine to form isoniazid-pyridoxal hydrazone. Pyridoxal-5-phosphate is necessary for the functioning of the enzymes glutamic acid decarboxylase and GABA transaminase which function in the GABA synthesis pathway. Thus isoniazid decreases the synthesis of GABA. Since GABA is an inhibitory neurotransmitter, deficiency of GABA can lead to increased excitatory action and siezures.
Pyridoxine 10 mg per day can be used to prevent peripheral …

Amoxycillin is an extended spectrum aminopenicillin. But it is not active against penicillinase producing organism. Clavulanic acid is a penicillinase inhibitor which initially reversibly and then irreversibly inhibits penicillinase 2-5 except cephalosporinase. So this drug combination has a synergistic action.

Sulphonyl ureas – first generation (tolbutamide, chlorpropamide); second generation – (glibenglamide, glipizide, gliclazide, glimiperide)
Biguanides – metformin
Meglitinides – repaglinide, nateglinide
Thiazolidine diones – rosiglitazone, pioglitazone
Alpha glucosidase inhibitors – acarbose, miglitol
Dipeptidyl peptidase-4 (DPP-4) inhibitors – sitagliptin
Glucagon like peptide (GLP-1) analogue – exenatide

Glibenclamide is an oral hypoglycemic drug belonging to the group sulphonyl ureas. It is a second generation sulphonyl urea. Other sulphonyl ureas include – glipizide, gliclazide and glimiperide.
Mechanism of action
It acts by increasing the release of insulin from the pancreatic beta cells. Glibenclamide acts by binding to sulphonyl urea receptor of the ATP sensitive potassium channel in the pancreatic beta cells. This reduces conductivity of the channel, which causes depolarisation of the pancreatic beta cells, resulting in the opening of voltage sensitive calcium channels. Opening of the channels cause calcium …

It is an antihelminthic drug, a newer congener of mebendazole.  Mechanism of action is same as that of mebendazole. It inhibits glucose uptake into the helminth’s cells and depletes the glycogen storage. This is by binding to the beta-tubulin and preventing its polymerisation. Microtubules within the cells of the helminths disappear. The drugs inconsistently absorbed from the intestine. Absorption can increased by giving along with a fatty meal.
Adverse effects
Mostly GI symptoms, alopecia
Uses
Single dose 400 mg albenazole is given for hook worm, ascarias, enterobius. 400 mg daily for 3 days is …

Metronidazole is a nitro-imidazole drug which has antiprotozoal and anti-anaerobe activity.
Spectrum
Protozoans - Entamoeba histolytic, Giardia lamblia, Trichomonas vaginalis
Bacteria – Camphylobacter jejuni, Helicobacter pylori, Fusobacterium, Bacteriodes fragilis, Spirochaetes, Clostridium perfringens, Clostridium difficile
Mechanism of action
Metronidazole has a nitro group which is converted into nitro radicle by the redox proteins of anaerobes. This acts as an electron acceptor and the availability of electrons to the electron transport chain is reduced. Certain organizms develop resistance to metronidazole by preventing the generation of nitro radicle.
Pharmacokinetics
Metronidazole is completely absorbed from the intestine and very little reaches the …

Methylergometrine produces non-physiological spasmodic contraction of the uterus in moderate to high doses and the uterus does’nt fully relax between the contractions. It also causes contraction of the lower segment of uterus. So the delivery of the fetus can be affected.
It is used after the delivery of the shoulder of the infant to reduce post partum hemorrhage. But it is indicated only in cases which have a higher risk of post partum hemorrhage.