OTC analgesics & antipyretics

dr.Hazemdr.Hazem مدير عام
OTC analgesics & antipyretics

OTC drugs available:
salicylates (aspirin, choline salicylate, Mg salicylate and Na salicylate)
Paracetamol (acetaminophen)
Naproxen Na

All are similar but Naproxen has slightly a longer duration of action

The strength of these products available OTC is less than same products available on prescription
Onset of all of these drugs is ½-1 hr, maximum effect between 2-3 hrs and duration of action is 4-6 hrs.
All will reduce temp by (1.1°- 1.7°C),

Active moiety: salicylic acid (irritating)
Choline salicylate: stable in oral solution
Mg salicylate + Na salicylate: can be used for patients allergic to aspirin
Inhibit COX in periphery and CNS

Indication: (1) mild to moderate pain of musculoskeletal NOT visceral origin. (2) Fever

- ASA is absorbed by passive diffusion of the nonionised from from the stomach/small intestine
- Factors affecting absorption (=5, what are they?)
- Rectal absorption is slow and unreliable (60-75%)
Enteric-coated ~:
1. Eliminates local gastric irritation
2. Delayed absorption by food (why?)
3. Not suitable for acute pain relief. Preferred for RA (why?)
Buffered ~:
1. no difference in gastric damage from plain ASA
2. Absorbed more rapidly than non buffered ASA
Effervescent ~: rapidly absorbed, but no evidence if rapid analgesia. Avoid in patients with restricted Na+ intake (CHF, RF, HTN)
Therapeutic Considerations:
1. Impaired platelet aggregation
acetyl group (good and bad?!!)
ASA should be D/C 48 hrs before surgery and shouldn’t be used as analgesic in dental extraction, or surgery etc
C/I: haemophilia, hypoprthrombinemia, vit K deficiency, Hx of bleeding or PUD

The prostaglandin thromboxane A2 (TxA2)  causes platelets to aggregate

Aspirin inhibits synthesis of TxA2 by irreversible acetylation of COX enzyme.

Other salicylates & NSAIDs also inhibit COX but have a shorter duration of inhibitory action because they cannot acetylate COX; that is, their action is reversible.

. Effect on uric acid elimination (dose-dependent)
Avoid all salicylates in all patients with Hx of gout or hyperuricemia (why?)

1-2 g/day plasma level of uric acid
2-3 g/day little/ no effect
> 5 g/day plasma level of uric acid

3. GI irritation & bleeding
two mechanisms of gastric damage (what are they?)
Avoid in: elderly, PUD or bleeding, alcoholic liver disease
Ingesting alcohol + ASA= incidence of GI bleeding
4. Aspirin Allergy
- If you experience gastritis or heart burn after aspirin use
Aspirin allergy is uncommon, < 1% of patients
within 3 hours of ASA ingestion: urticaria, oedema, difficulty in breathing, rhinitis, bronchospasm or shock
Most common in patients with asthma, urticaria or nasal polyps
15% cross-reaction with Tartrazine (colour)
Cross reaction with other NSAIDS (rate for acetaminophen 6% and for ibuprofen 97%)
patients allergic to ASA > avoid all NSAIDs > use acetaminophen or nonacetylated salicylates (eg, Na salicylate) instead

5. Pregnancy/ Lactation
- Avoid ASA in both
Avoid ASA especially during the 3rd trimester/pregnancy
Why? > Effect on mother (=3), effect on fetus (haemorrhage, growth retardation, congenital intoxication, premature closure of ductus arteriosus > still birth)
Paracetamol is the analgesic of choice in these periods

Unlabelled/Investigational Use:
Low doses have been used in the prevention of pre-eclampsia, recurrent spontaneous abortions, pematurity, fetal growth retardation (including complications associated with autoimmune disorders such as lupus)
60-80 mg/day during gestational weeks 13-26 (patient selection criteria not established)
6. Reye’s Syndrome
Acute potentially fatal illness (50%) occurs almost exclusively in children < 15 years of age
Produces fatty liver + encephalopathy
Occurs usually within 1-7 days of viral infections with influenza or chickenpox.
Ch.Ch: persistent vomiting, CNS damage, signs of hepatic injury & stupor > convulsions > coma
Nonacetylated NSAIDs > not associated with Reye’s

Aspirin toxicity
with chronic therapy (100 mg/kg per day for at least 2 days)> mild intoxication- HA, dizziness, N & V, hyperventilation, mental confusion, lassitude….
Acute intoxication- dose-dependent:
<150 mg/kg mild
150-300 mg/kg moderate
>300 mg/kg severe

Symptoms: lethargy, tinnitus, tachypnea, pulmonary edema, convulsions, coma, haemorrhage and dehydration.
First respiratory alkalosis followed by metabolic acidosis (why?)
Hypoglycemia (why?) and fever may be severe in children.
Bleeding from GIT or mucosal surface > petechiae at autopsy

OD Management: ipecac syrup, gastric lavage, activated charcoal
Administration of ipecac syrup or any oral solution to a pt who’s convulsing is absolutely C/I aspiration
in children < 1yr old > vomiting should be induced only under medical supervision


  • dr.Hazemdr.Hazem مدير عام
    تم تعديل 2010/05/03
    Non-acetylated salicylates

    choline salicylate:
    an oral liquid preparation
    Fishy odour> mask by fruit juice, carbonated beverages, water but NOT alkaline solution (eg. Antacids; why?)
    Not as effective antipyretic as ASA or acetaminophen in children
    Hydrolysed by cutaneous esterases to salicylic acid that has anti-inflammatory effect
    However, The British National Formulary (2007) states that choline salicylate is of doubtful value when used topically

    Mg salicylate:
    - avoid in case of compromised renal function
    - could be used by ASA allergic patients

    Na salicylate:
    - avoid in patients with Na restriction intake
    - could be used by ASA allergic patients
    Comparison of aspirin and non-acytelated salicylates

    Less effect on platelet aggregation
    Less GI erosions and bleeding
    Fewer renal complications
    cross-reactivity in aspirin intolerant patients
    Less anti-inflammatory effect
  • the-aspirantthe-aspirant المشرف العام
    تم تعديل 2010/05/03
    مشكور حكيم....يجب ألا ننسى الأسبرين وغيره من الساليسيلات وتأثيرها المخرش لمخاطية الجهاز الهضمي
  • dr.Hazemdr.Hazem مدير عام
    تم تعديل 2010/05/03
    كلامك صحيح ..شكراً و بارك لله فيك..
  • dr.Hazemdr.Hazem مدير عام
    تم تعديل 2010/05/04

    An effective analgesic and antipyretic (works centrally), weak anti-inflammatory (not used clinically for this purpose)
    Used for mild to moderate pain of non-visceral origin
    Paediatric dose= 10-15 mg/kg q 4-6 hrs
    Adult dose: 325-650 mg q 4-6 hrs or 1000 mg 3-4 times daily (do not exceed 4g/day)
    Rectal bioavailability=50-60% (compare with ASA)
    Children tips!

    capsule content > emptied into a teaspoon containing a small amount of drink or soft food and NOT into a glass of liquid (why?)
    Mixing with a hot beverage can result in bitter taste.

    Paracetamol- Overdose

    Hepatotoxicity after ingestion of a single dose of 10-15 g (150-250 mg/kg)
     20-25 g  fatal
    first 2 days: abdominal pain, N & V, drowsiness, confusion
    2-4 days: clinical manifestaions of hepatotoxicty: ALT & AST, bilirubin in plasma, prothrombin time
    The most serious Ad.E of acetaminophen OD is Hepatic Necrosis (dose dependent)
    Renal tubular necrosis and hypoglycemic coma may also occur
    Management: immediate vomiting induction by ipecac syrup and activated charcoal
    If activated charcoal was used at home > should be made known to emergency medical personnel (why?)
    Therapeutic Consideration
    Acetaminophen is safe in pregnancy and breast-feeding
    The only Ad. E in nursing infants is a rarely occurring maculopapular rash
    ~ is hepatotoxic if > 4 g/day especially for people at risk

    Avoid alcohol and fasting while using paracetamol

    No significant D#D interactions with paracetamol
    Recent research: effect of warfarin may be enhanced (??)
  • dr.Hazemdr.Hazem مدير عام
    تم تعديل 2010/05/06
    Indications: mild to moderate pain of non-visceral origin & dysmenorrhoea. Antipyretic and anti-inflammatory

    ibuprofen >> aspirin or other salicylates or acetaminophen for the relief of dysmenorrhoea

    Dose: for those > 12 years old, 200-400 mg q 4-6 hrs not to exceed 1,200 mg per day

    Overdose: asymptomatic (43%) or minimal symptoms (abd pain, N&V, lethargy, dizziness..)

    Therapeutic Considerations

    Less gastric bleeding and ulceration than ASA (S.E: dyspepsia, heartburn, Nausea, anorexia, epigastric pain)
    Ibuprofen effect on platelet aggregation, unlike that of ASA, is reversible within 24 hours.
    Caution: avoid using alcohol or warfarin+ ibuprofen prolongation of prothrombin time
    Patients with Hx of impaired renal function, CHF or diseases that compromise the renal haemodynamics should not self-medicate with ibuprofen (why?) because ibuprofen reduces the renal blood flow and GFR by inhibiting the synthesis of renal prostaglandins BUN and serum creatinine
    C/I: in aspirin intolerant patients (cross reaction 97%).
    C/I: in 3rd trimester of pregnancy (similar effect to ASA)
    compatible with breast-feeding
  • dr.Hazemdr.Hazem مدير عام
    تم تعديل 2010/05/07
    Very similar to Naproxen and ibuprofen except that label advise to avoid in nursing mothers.
    Not teratogenic/toxic during pregnancy but it should not be used (similar effect to ASA)
    Not recommended for patients < 16 year old
    Dose: > 16 years 12.5 mg q 4-6 hours (maximum 75 mg/day), may take a second dose after 1 hour if needed.
    1 tablet of ketoprofen (12.5mg) is equivalent to 1 tablet (200 mg) of ibuprofen.
    Comparative efficacy:
    ASA and paracetamol >> same effectiveness
    ibuprofen at least as effective as ASA in analgesia
    as effective as but not superior to ASA in managing RA
    Ibuprofen superior to paracetamol in analgesia and anti-inflammatory effects. But as effective as paracetamol as an antipyretic.
    Naproxen and ibuprofen v similar
    Combination Products:
    active ingredients (e.g. ASA, ibuprofen or paracetamol) are sometimes mixed with caffeine or antihistamines in OTC products to enhance the analgesia

    Combinations of such active ingredients with decongestants (e.g. phenylphrine) are useful in treatment of sinus headaches.