KEY LEARNING POINTS
- Penicillins, the first antibiotics used clinically in 1941, interfere with the synthesis of the bacterial cell wall by binding to penicillin-binding proteins (PBPs). They are classified into natural penicillins, penicillinase-resistant penicillins, aminopenicillins, antipseudomonal penicillins, carboxy-penicillins, ureido-penicillins, and B-lactamase inhibitors.
- Some common natural penicillins include Penicillin G and Penicillin V, while penicillinase-resistant penicillins include Methicillin, Cloxacillin, Nafcillin, and Oxacillin. Aminopenicillins like Amoxicillin and Ampicillin have extended spectrum activity against Gram-negative bacteria.
- Antipseudomonal penicillins like Carbenicillin, Ticarcillin, and Piperacillin are effective against Pseudomonas aeuroginosa and Proteus species. B-lactamase inhibitors such as Clavulanic acid and Sulbactam are often used in combination with antibiotics to overcome bacterial resistance.
- Cephalosporins are another class of antibiotics commonly used in ENT & Otolaryngology. They are classified into five generations based on their spectrum of activity and resistance profiles. The generations range from the first (cefadroxil, cephalexin) to the fifth (Ceftobiprole, Ceftaroline).
- Each generation of cephalosporins has varying activity against different types of bacteria. For example, first-generation cephalosporins are effective against most Gram-positive bacteria except MRSA, while fourth-generation cephalosporins like Cefepime are effective against resistant hospital-acquired infections.
- Other important antibiotics used in ENT & Otolaryngology include Monobactams (Aztreonam), Carbapenems (Meropenem, Imipenem), and Glycopeptides (Vancomycin). These antibiotics have specific indications and are effective against different types of bacterial infections.
- It's crucial to consider the spectrum of activity, resistance patterns, and potential side effects of antibiotics when choosing the appropriate agent for treating ENT & Otolaryngology infections. Working with a healthcare provider to determine the most effective antibiotic therapy is essential for successful treatment outcomes.- Drug choice for anti-inflammatory action: Diphtheria 250 mg-500 mg orally 6hrly for 10 days, Roxithromycin 150 mg daily, or placebo
- Long-term low dose studies needed for assessing efficacy
- Antibiotic therapy benefits in Atypical mycobacterial infections
- Roxithromycin can decrease polyp size in 52% of patients
- Clindamycin (Lincosamides) for severe anaerobic mixed infections like parotid abscess
- Aminoglycosides like Gentamicin and Tobramycin for gram-negative bacilli and S. aureus infections
- Tetracyclines like Doxycycline for broad-spectrum coverage including Staph aureus, pneumococci, and atypical bacteria
- Linezolid and Quinipristin/Dalfopristin for specific infections like MRSA, VRE
- Fluoroquinolones like Ciprofloxacin for various indications including perichondritis and otitis externa
- Metronidazole for anaerobic infections and antiprotozoal activity
- Trimethoprim-Sulphonamides for gram-positive and negative bacteria, Chlamydia trachomatis, and nocardia
- Antitubercular drugs like Isoniazid, Rifampicin, Pyrizinamide, and Ethambutol with their respective side effects and mechanisms of action
- New antitubercular drugs being researched like Fluoroquinolones, Diarylquinolines, and Nitroimidazopyrans
- Overview of antihistamines, their sedative potency, subtypes, and clinical uses in allergic disorders, common cold, motion sickness, and vertigo
- Olopatadine hydrochloride (0.6%) is used for seasonal allergic rhinitis, with a recommended dosage of 2 puffs per nostril twice daily.
- Common side effects of Olopatadine hydrochloride include bitter taste and somnolence.
- Vertigo can be managed with various types of drugs, including labyrinthine suppressants, anticholinergics, antiemetics, vasodilators, diuretics, and corticosteroids.
- Labyrinthine suppressants like Cinnarizine, Dimenhydrinate, and promethazine work by reducing vertigo symptoms.
- Antihistamines like Cinnarizine can selectively antagonize T-type voltage-operated calcium ion channels, providing relief from vertigo.
- Betahistine hydrochloride is a histamine analog that acts as a weak postsynaptic H1 receptor agonist and a presynaptic H3 receptor antagonist, which can help increase cerebral and vestibular blood supply.
- Prochlorperazine is an effective drug for controlling violent vertigo and vomiting, especially when administered parenterally.
- Common side effects of Betahistine hydrochloride include headache, nausea, hypersensitivity, and indigestion.
- Cinnarizine, another drug used for vertigo, binds to histamine receptors and has antihistaminic, antiserotoninergic, and antidopaminergic effects.
- Common side effects of Cinnarizine include drowsiness, sweating, dry mouth, headache, and extrapyramidal symptoms.
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ANTIBIOTICS & ANTIHISTAMINE AGENTS IN ENT & OTOLARYNGOLOGY
Antibiotics
Antibiotics classification
Mechanism of action
Broad / narrow spectrum
Bactericidal / Bacteriostatic
β-lactam Antibiotics
share similar
• features of chemistry
• mechanism of action
• pharmacologic and
clinical effects
Penicillin
Classification:
Natural penicillin :
Penicillin G (narrow spectrum, acid labile, short acting)
Penicillin V (orally active derivative of PnG)
Penicillinase resistant penicillin (methicillin, cloxacillin, nafcillin, oxacillin)
Aminopenicillin (amoxicillin, ampicillin)
Antipseudomonal penicillins
Carboxy-penicillins : Carbenicillin, Ticarcillin
Ureido-penicillins : Piperacillin, Mezlocillin
B lactamase inhibitors: Clavulanic acid, Sulbactam
Pharmacokinetics: penicillin
Absorption of most penicillin is impaired by food and drug should be administered 1-2 hours before or after food (amoxycillin is an exception)
Excretion : via tubular secretion (90%) with secretion blocked by probenecid
dose reduction : renal dysfunction
Nafcillin and oxacillin eliminated largely in bile
Benzathine penicillin G -repository form (half-life of 2 weeks)
Penicillin : side effects
Hypersensitivity reactions (<10%) – pencilloic acid*
Anaphylaxis – 0.004% and 0.015% of penicillin courses -highest with procaine * Interstitial nephritis (m/c : Methicillin), CNS toxicity (high doses- seizures)
Reversible Neutropenia (Nafcillin) and hepatitis (Oxacillin)*
Jarish-herxheimer reaction in the management of syphilis
GI distress and rash due to ampicillin ( contraindicated in infectious mononucleosis) *
Diarrhoea incld C.difficile ( > asso ampicillin and amoxicillin)
By inhibiting colonic flora – interfere enterohepatic circulation of OCPs- failure may occur
*Lippincot’s pharm, 5th ed and KD Tripathi 7th edition
Penicillin -G ( Benzyl Penicillin)
Preparations:
Crystalline penicillin ( sodium penicillin G) : 0.5 - 5 MU i.v./i.m. 6-12 hrly
Repository preparations:
Procaine penicillin G : 0.5-1 MU i.m 12-24 hrly
Benzathine penicillin G : 0.6-2.4 MU i.m
Penicillin V
Phenoxymethyl penicillin, Acid stable
Less coverage for Neisseria and other gm negatives and anaerobes
Penicillin V 250-500 mg (25-50 mg /kg/day) orally 6 hrly for 10 days
- gold standard of treatment for Acute tonsillopharyngitis
~ 25% Strep. Pneumonae are resistant to penicillin and additional 25% resistant to more than one antibiotic
Antistaphylococcal penicillins
Cloxacillin, Flucloxacillin, Oxacillin
Penicillinase resistant penicillin
250-500mg 6 hrly in adults , 0.25 to 1 g i.v. 6 hrly
<20 kg 50-100 mg/kg/day Q6h
Indication : Acute otitis externa, Furunculosis, Nasal vestibulitis, Septal abscess
Resistance – altered penicillin binding protein 2a
Upto 30% incidence of MRSA
S/E: Hypersensitivity reactions, G.I. disturbances, Hepatic impairment
Aminopenicillins
Extended spectrum of action – Gm –ve bacilli
Amoxycillin, Ampicillin
Amoxycillin 500 mg oral 8 hrly
Children: 25-50 mg/kg/day q8h
Ampicillin 500 mg i.v. 6 hrly ( children 25-50 mg/kg/day)
Indication
Acute otitis media (1st line ) (IDSA 2012 guideline)
Acute tonsillopharyngitis
Acute rhinosinusitis
Acute supraglottitis
Antipseudomonal penicillin
Carbenicillin, Ticarcillin, Piperacillin
Pseudomonas aeuroginosa, Proteus sps
Synergistic activity with gentamycin
Psuedomonas septicaemias esp. in neutropenia or endocarditits
100-150 mg/kg/day i.m./ i.v. in three divided doses
S/E: hypersensitivity reaction, Stevens-Johnson syndrome, Toxic epidermal necrolysis, hypernatraemia
β-lactamase inhhibitors
Clavulanic acid, sulbactam
Co-Amoxyclav (Amoxycillin + clavulanic acid) 625 mg oral 8hrly or 1.2 gm i.v. 8 hrly
Indications:
2nd line in Acute otitis media,
Acute bacterial tonsillopharyngitis
As a preoperative antibiotic in cochlear implant patients
Acute and chronic rhinosinusitis
Acute bacterial rhinosinusitis : amoxicillin-clavulanate, rather than amoxicillin alone, is recommended as empiric antimicrobial therapy for ABRS in both adults and children (IDSA 2012 guidelines)
Penicillin: synergistic action
Ampicillin + Cloxacillin
1 gm oral/ i.v. 6 hrly
Deep neck abscess, Peritonsillar abscess, A. tonsillopharyngitis (recurrent), Chronic otitis media
Penicillin + gentamycin : increases transport of gentamycin in cells
mixed gram positive and negative infections against pseudomonas and enterococci (deep neck space infections)
Ampicillin 1 gm + sulbactam 0.5 gm i.v. 8 hrly – ICU setting
s/e: cholestatic jaundice
Cephalosporins : classification
1st generation cephalosporins
Pneumococci, streptococci, staphylococci except MRSA
Cefadroxil/cefazolin alternative to antistaphylococcal penicillin
Cefazolin 0.5 – 2 gm i.v. 8 hrly ( only i.v. drug in use) – used in surgical prophylaxis
Cefadroxil 0.5 – 1 gm orally 12 hrly ( children: 30mg/kg/day Q12h) for minor soft tissue infections
2nd generation cephalosporins
Cefuroxime - active against penicillin resistant pneumococci
250 – 500 mg orally 12 hrly (children : 30mg/kg/day)
2nd line in Acute otitis media, Acute rhinosinusitis, lower respiratory tract infections
3rd generation cephalosporins
Expanded gm negative coverage
Antipseudomonal activity of ceftazidime and cefoperazone
Cefixime, ceftibuten less active against pneumococcus
Indication:
Ceftriaxone 1 gm i.v. 12 hrly (children: 50-75 mg/kg/day) for serious infections like deep neck abscess, mastoiditis
As preoperative antibiotics
2gm i.v. 12 hrly – meningitis dose
- used in febrile neutropenic, immunocompromised patients
4th generation cephalosporins
Same antibacterial spectrum but more resistant to the B-lactamases
Antipsuedomonal
Cefepime 0.5 – 2gm i.v. 12 hrly (75-120 mg/kg/day)
Serious and resistant hospital acquired infections including septicaemia
Side effects
Common:
Pain at injection site
Diarrhoea, nausea
Rash, electrolyte disturbance
Infrequent :
Vomiting, headache, dizziness
Superinfection , pseudomembranous colitis, oral and vaginal candidiasis
Eosinophilia , fever
Hypoprothrombinemia and disulfiram like reactions can occur with
cefoperazone, cefamandole, cefotetan and moxalactam.
Monobactam (Aztreonam)
Relatively resistant to B-lactamases (properties similar to ceftazidime)
No activity against gm positive bacteria or anaerobes
Active against gm negative rods including pseudomonas
Aztreonam 1-2 gm i.v. 8 hrly in hospital acquired infections (urinary, biliary, GItract)
Useful in patients with hypersensitivity to penicillins/ cephalosporins
Carbapenems
Meropenem has greater activity against gm negative aerobes and less activity against gm positive serious hospital acquired resistant infections, ICU settings
Imipenem: 250 mg-500 mg i.v. 6-8 hrly
(combined with cilastatin - inhibits dehydropeptidase I on brush border of renal tubular cells)
Meropenem: 1gm i.v. 8 hrly
Side effect : GI disturbances, skin rash, reaction at infusion site, seizures (less with meropenem), cross sensitivity with penicillins
Resistant to most B-lactamases
Glycopeptides
Only have Gm positive activity
Esp. against MRSA, or in penicillin hypersensitivity
Affect bacterial CW synthesis by binding to the D-alanine of the peptide chain hence inhibiting the cross-linking process
Vancomycin :
500 mg-1 gm i.v. 12 hrly (children: 10-15 mg/kg/day q6h) in slow infusion
125 mg orally 6 hrly ( children: 40-50mg/kg/day q6h) in Clostridium difficile infection
Vancomycin
Side effects –
Red man syndrome( chills, fever, urticaria, intense flushing),
Renal toxicity (concomitant use of aminoglycoside)
Ototoxicity: severe SNHL is reported
(ototoxicity potentiated by concomitant aminoglycoside, impaired renal function)
Resistance : caused primarily by an acquired resistance from the VRE : vanA gene
Protein synthesis and modes of action of antibacterial drugs
Macrolide
Large lactone ring to which sugars are attached
Erythromycin
Clarithromycin
Azithromycin
Telithromycin
Spiramycin
Tacrolimus
Macrolide : indication
Used as an alternative to penicillin against GABHS pharyngitis, Acute otitis media
Acute bacterial rhinosinusitis: Anti-inflammatory action ( goblet cell secretion, ciliary function) long-term low dose – placebo controlled RCTs needed
Drug of choice in diphtheria
250 mg-500 mg (40 mg/kg/day) orally 6hrly for 10 day
Roxithromycin 150 mg daily or placebo for 3 months : significant improvement in subjective symptoms, disease-specific QOL and endoscopy findings compared with placebo (P ≤ .01 ) (Wallwork et al.,2006)
Atypical mycobacterial infections
Decrease in polyp size in 52% of patients after 8 wks use of roxithromycin (Ichimura et al., 1996)
3 months course beneficial in management of CRS (Raqab SM et al, 2004)
S/E: epigastric pain, diarrhoea, nausea (increase gastric motility) very high dose- reversible hearing impairment, acute cholestatic hepatitis, drug interactions
intravenous preparations are associated with thrombophlebitis
LINCOSAMIDES - Clindamycin
Similar spectrum of activity as erythromycin, additional anti-anaerobic action
Use: severe anaerobic and mixed infections
Parotid abscess/ suppurative partotitis
Dose : 150-450 mg PO q6h, 600-900 mg iv q8h
children 20-40 mg/kg/day q6-8h
S/E : Pseudomembranous colitis, SJ syndrome,
Rare – granulocytopenia, neutropenia, thrombocytopenia.
Aminoglycosides
Neomycin, Gentamycin, amikacin,
tobramycin, streptomycin, kanamycin,
netilmicin
active in gram negative bacilli, S. aureus,
mycobacteria and Brucella, but no anaerobic activity
Concentration dependent killing and postantibiotic effect
Topical:
- Gentamycin 0.3% ear drop
- Tobramycin 0.3% ear drop
- Neomycin 0.5% + Polymixin B 0.05% + Dexamethasone 0.1% ear drop in active otorrhoea in COM
Aminoglycosides
Indications:
Systemic use in severe deep neck infections with B-lactams
Streptomycin as antitubercular (15 mg/kg/day) drug
Side effect – ototoxicity and nephrotoxicity, neuromuscular paralysis
Topical therapy is ototoxic in animals but no conclusive evidence in humans , but vestibular toxicity has been reported (Bath et al., 1999)
Tetracyclines
Bacteriostatic, bind to 30S blocking the acceptor site of t-RNA
Maximum absorption by oral route: doxycycline and minocycline
Impaired by food, milk and antacid.
Broad spectrum – staph aureus, pneumococci, H. Influenzae, gonococci , some anaerobes and atypical bacteria
Doxycycline 100 mg orally 12 hrly for 10 days in Chronic rhinosinusitis (good alternative to amoxyclav) (IDSA 2012)
S/E: pseudo membranous enterocolitis, teeth discoloration, deformity or growth inhibition in children, pseudo-tumour cerebri, fanconi syndrome by old and outdated ones.
Chloramphenicol
Binds to 50S subunit and inhibits peptide formation
Bacteriostatic broad spectrum active against both aerobic and anaerobic , gram positive and negative organisms.
Chloramphenicol 5% ear drops – active COM
S/E – Grey baby syndrome (due to a lack of hepatic enzyme activity with build-up of unconjugated chloramphenicol, resulting in circulatory collapse)
In adults: reversible dose-dependent bone marrow suppression
1 in 40,000 patients develop an irreversible aplastic anaemia
Streptogramins (bacteriocidal)
Quinipristin/dalfopristin (3:7 w/w)
Inhibit protein synthesis (50s ribosome)
Gm positive, atypical microbial infection
Active against – MRSA,VRSA, VRE
7.5 mg /kg i.v. od infusion into central vein for 7 days in skin and soft tissue infection
S/E: arthralgia-myalgia syndrome, injection site reaction in peripheral vein, hypersensitivity reactions
Oxazolidinones
Linezolid (bacteriostatic)
Bind to 23S subunit of 50S inhibits initiation of protein synthesis
Activity against MRSA, VRSA, VRE, Penicillin resistant streptococci
600 mg PO/iv q12h (children <5 years: 10mg/kg PO q8h, > 5yrs q12h)
S/E: Optic and peripheral neuropathy, lactic acidosis, glossitis, stomatitis, renal failure, stevens-johnson syndrome, pancytopenia (thrombocytopenia)
Maximum recommended duration = 28 days
Antibacterial drugs acting on DNA
Quinolones
Indication : quinolones
Indications: Perichondritis, malignant otitis externa – antipseudomonal agent
Ciprofloxacin 500 – 750 mg orally 12 hrly
Levofloxacin 250 – 500 mg orally daily
Respiratory fluoroquinolones : Moxifloxacin, in acute bacterial rhinosinusitis
- comparable to β-lactams for the treatment of acute bacterial sinusitis, in terms of the clinical cure and improvement and the safety outcome
- may be used in case of resistance to β – lactams (Drosos et al., 2008)
2nd line agent for Tuberculosis
Resistance: misuse as in URTI and skin and soft tissue infections
Side effect : nausea, vomiting, diarrhoea, photosensitivity, abnormal liver function test, tendinitis, seizures, interaction with theophyllines
Avoided in pregnancy and lactation
Metronidazole
Disrupts DNA synthesis leading to cell death
Strictly anaerobic bacteria esp. Bacteroides fragilis, Clostridium difficile, and Clostridia species
Antiprotozoal activity – E. histolytica, Giardia
Metronidazole 400 mg orally 8 hourly / 500mg i.v. 8 hourly (15mg/kg/day q8h)
Well absorbed orally and penetrates tissues and crosses the blood–brain barrier.
Metronidazole : Indication
Along with B- lactams in mixed infections like peritonsillar abscess, deep neck abscess, mastoiditis, septal abscess
Topical gel used in for dressing fungating tumours
Side Effects : nausea, dry mouth, disulfiram like effect, dizziness, metallic taste, peripheral neuropathy and encephalopathy (long-term treatment)
Inhibitors of tetrahydrofolate synthesis
Sulphonamides and Trimethoprim
Bactericidal
Inhibit gm positive and negatives, chlamydia trachomatis, nocardia
Useful alternative to B – lactams in URTI
Cotrimoxazole : (Sulphamethoxazole and trimethoprim in 5:1 ratio)
Double strength (800:160) tablet orally 12 hrly (8mg/kg + 40 mg/kg)
S/E: megaloblastic anaemia, leukopenia, granulocytopenia, severe allergic skin rash inc. Stevens Johnson syndrome, more in AIDS patients
Given in combination, sequentially inhibits nucleotide synthesis
Antimicrobial therapy in ENT : evidence
Acute bacterial rhinosinusitis :
Amoxicillin-clavulanate, rather than amoxicillin alone, is recommended as empiric antimicrobial therapy for ABRS in both adults and children
Macrolides (clarithromycin and azithromycin) are not recommended : resistance with S. pneumoniae (~30%)
(IDSA 2012 guideline)
Antitubercular drugs
Isoniazid: Inhibit synthesis of mycolic acid, most active drug
s/e: fever, skin rash, hepatotoxicity, peripheral neuropathy
Rifampicin: Inhibits DNA dependent RNA polymerase and transcription
Good intracellular penetration, bactericidal
s/e: red discoloration of body fluids, flu like syndrome, anaemia, thrombocytopenia, shock, hepatitis
Pyrizinamide: Mechanism unknown
Bactericidal
s/e: hepatotoxicity, hyperuricaemia
Ethambutol:
Inhibitor of mycobacterial arabinosyl transferase disruption of cell barrier
Bacteriostatic, enhances activity of other ATD
s/e: retrobulbar neuritis, pruritus,
Second line ATT
Kanamycin
Pyrazinamide
Levofloxacin
Ethionamide
Cycloserine
New antitubercular drugs in research
Fluoroquinolones: moxifloxacin,gatifloxacin
Diarylquinolines: TMC207 , phase II clinical trials at a dose of 400 mg/day
inhibits the mycobacterial ATP synthase enzyme
2 month regime of once weekly HRZ+ TMC207, more effective than daily dosing of HRZE
Nitroimidazopyrans: PA-824, inhibits the synthesis of proteins and cell wall lipids, 100 mg/kg
OPC-67683 : mycolic acid biosynthesis inhibitor- faster eradication of bacilli
Antihistamines
Histamine receptor subtypes
H1 - antihistamines
Sedative potency
Highly sedative:
Diphenhydramine,Promethazine
Moderately sedative :
Pheniramine, Cyproheptadine, Meclozine, Cinnarizine
Mild sedative:
Chlorpheniramine, Cyclizine
More frequent with first generation – sedation, diminished alertness, light headedness, motor incoordination, fatigue, tendency to fall asleep, impaired psychomotor performance – caution to operate vehicles, machineries
Dryness of mouth, epigastric
ness, urinary hesitancy, blurring of vision
Second Generation:
Second Generation:
Terfenadine, Fexofenadine, Astemizole, Loratadine, Ebastine
Higher H1 selectivity: no anticholinergic side effect
No/Less CNS depression
Additional antiallergic mechanism – inhibit late phase allergic reaction by acting on Leukotrienes.
Clinical uses : antihistamines
Allergic disorders : itching, urticaria, seasonal hay fever, allergic conjunctivitis, angioedema, allergic rhinitis
Common cold
Motion sickness
Vertigo : cinnarizine, betahistine.
Insect bite , ivy poisoning.
Adverse effects : antihistamines
Sedation : more common with first generation, additive effect with alcohol
Antimuscarinic effects : dry mouth and respiratory passages, urinary retention, and dysuria
Nausea, vomiting, constipation or diarrhea
Dizziness, insomnia, nervousness, and fatigue
Terfenadine and astemizole : torsades de pointes
Regular use of antihistamines in children is not advisable because the CNS depressant properties might interfere with learning and academic task.
Antihistamines : evidence
Allergic rhinitis : Effective in controlling sneezing, itching, rhinorrhea, and eye symptoms but minimally effective in alleviating nasal congestion (Simons.,2014)
Common cold : some general benefit in adults and older children
(Cochrane review.,2012)
OME : no benefit in long term outcome (Cochrane review.,2011)
Acute sinusitis in children : data not sufficient (Cochrane review.,2014)
Antihistamine : intranasal spray
Azelastine : for allergic rhinitis, twice daily
comparable efficacy to other antihistamines
effective in reducing itching, sneezing, runny nose, and nasal congestion (LaForce et al.,2004)
S/E : somnolence
Olopatadine hydrochloride (0.6%) : for seasonal allergic rhinitis , 2 puffs/ nostril twice daily ( Meltzer et al., 2007)
S/E : bitter taste, somnolence
Drugs for Vertigo
1. Labyrinthine suppressants:
Antihistaminics: (with anticholinergic actions)- Cinnarizine, Dimenhydrinate, promethazine.
Anticholinergic: Atropine, Hyoscine
Antiemetics phenothiazines: Prochlorperazine, Thiethylperazine.
2. Vasodilators: Improve blood flow to labyrinth and brainstem: Betahistine, nicotinic acid.
3. Diuretics: decrease labyrinthine fluid pressure: Thiazides, amiloride, acetazolamide.
4. Corticosteroids: suppress intralabyrnthine edema due to viral infection and other causes.
Parenteral prochlorperazine is the most effective drug in controlling violent vertigo and vomiting.
Histamine related drugs
Betahistine hydrochloride
structural histamine analog
weak postsynaptic H1 receptor agonist, presynaptic H3 receptor antagonist, also little H2 receptor activity
histaminergic effect : mainly by H3 antagonism
M/A: increases cerebral and vestibular system blood supply suppress vestibular nuclei
Evidence: not enough evidence for betahistine in Meniere’s disease (Cochrane review.,2011)
S/E : headache ,nausea, hypersensitivity, indigestion
Cinnarizine
selective antagonist of T-type voltage-operated calcium ion channels
Antihistaminic (H1), antiserotoninergic (5HT2) and antidopaminergic (D2) effects
binds to histamine receptors
safe and effective in reducing vertigo
S/E: drowsiness, sweating, dry mouth, headache, EPS
