Basic Medicine and Pharmacology

What to remember

• Pharmacology is the study of drugs: their sources, actions, uses and side effects. The health worker must know the six rights of drug administration and common doses.
• Drug dose calculations use simple formulas (desired dose ÷ available strength × volume), and children's doses depend on weight or age.
• Know the drug of choice for the common problems: ORS and zinc for diarrhoea, paracetamol for fever, oxytocin for postpartum bleeding, adrenaline for anaphylaxis, and the antidotes.

Basic terms

• Drug: any substance used to diagnose, treat, relieve or prevent disease.
• Pharmacokinetics: what the body does to the drug: absorption, distribution, metabolism (mostly in the liver) and excretion (mostly through the kidney). Pharmacodynamics: what the drug does to the body.
• Bioavailability: the fraction of the dose that reaches the blood. It is 100% for intravenous drugs.
• Half-life: time taken for the blood level of a drug to fall by half.
• Side effect: an unwanted but expected effect. Adverse reaction: a harmful effect. Allergy: immune reaction. Toxicity: harmful effect due to an overdose. Tolerance: need for larger doses over time. Dependence: need to continue the drug.
• Generic name is the official name of the drug. Brand name is the manufacturer's trade name.
• Essential medicines: those that satisfy the priority health needs of the population. A national list guides government supply.
• Sources of drugs: plants (morphine, digoxin), animals (insulin, heparin), minerals (iron, magnesium sulphate), micro-organisms (penicillin) and synthetic (paracetamol).

Routes of administration

• Angles of injection: IM at 90 degrees, SC at 45 degrees (or 90 with a short needle in a skin fold), ID at 10 to 15 degrees.
• Injection site for infants: vastus lateralis (outer thigh). For adults, deltoid or gluteal sites. Avoid the gluteal route in small children.
• Use a new sterile needle and auto-disable syringe for each injection. Never recap needles. Dispose of sharps in a puncture-proof container.

Safe medication practice

• Six rights: right patient, right drug, right dose, right route, right time, right documentation. Some lists add right reason.
• Check: the label three times (when taking from the shelf, before pouring, and when returning), the expiry date and the colour and clarity of the drug.
• Ask about allergy before giving a new drug. Keep adrenaline ready for injections.
• Prescription abbreviations: OD = once daily, BD = twice daily, TDS = three times daily, QID = four times daily, HS = at bedtime, SOS or PRN = when necessary, STAT = immediately, AC = before meals, PC = after meals.
• Storage: keep in a cool, dry place away from light. Keep vaccines and oxytocin cold (2 °C to 8 °C). Keep controlled and poisonous drugs locked. Store by first expiry, first out.
• Drug laws: the Drugs and Cosmetics Act, 1940 controls manufacture, sale and distribution. Schedule H drugs need a doctor's prescription. Schedule X drugs are strictly controlled narcotic and psychotropic drugs.

Dose calculation

• Basic formula: dose to give = (desired dose ÷ strength on hand) × quantity of the preparation.
• Example 1: ordered 500 mg; tablets are 250 mg each. Number of tablets = 500 ÷ 250 = 2.
• Example 2: ordered 120 mg of paracetamol syrup; strength 125 mg per 5 ml. Volume = (120 ÷ 125) × 5 = 4.8 ml.
• Weight-based dose: dose = dose per kg × body weight. Paracetamol 15 mg per kg for a 12 kg child = 180 mg.
• Children's dose rules (approximate):
• Young's rule: child dose = [age in years ÷ (age + 12)] × adult dose. For a child of 4 years: 4 ÷ 16 = one-fourth of the adult dose.
• Clark's rule: child dose = (weight in kg ÷ 70) × adult dose.
• Fried's rule (infants): (age in months ÷ 150) × adult dose.
• Dilling's rule: (age in years ÷ 20) × adult dose.
• IV drip rate: drops per minute = (volume in ml × drop factor) ÷ time in minutes. With a 20 drops/ml set, 500 ml over 4 hours (240 minutes) = 500 × 20 ÷ 240 ≈ 42 drops per minute.
• Percentage solution: 1% means 1 g in 100 ml, i.e. 10 mg per ml.

Common drug groups and their use

Drugs and nutrients in national programmes

• ORS and zinc: the standard low-osmolarity ORS has sodium 75, glucose 75 and total osmolarity 245 mmol/L. Give zinc for 14 days: 20 mg daily to children above 6 months, and 10 mg to those under 6 months.
• Iron and folic acid: adult (pregnant/lactating) tablet under Anemia Mukt Bharat has 60 mg elemental iron and 500 mcg folic acid (the older norm was 100 mg). Side effects: black stools, nausea, constipation.
• Vitamin A prophylaxis: 1 lakh IU at 9 months, then 2 lakh IU every 6 months up to 5 years. Deficiency causes night blindness and xerophthalmia.
• Vitamin K is given to newborns to prevent bleeding disease.
• Calcium with vitamin D for pregnant women and for rickets.
• Albendazole: 400 mg after the first year of life (200 mg for ages 12 to 24 months).
• Paracetamol: 10 to 15 mg per kg per dose for children, every 4 to 6 hours. Adult maximum is 4 g per day.

Emergency drugs and antidotes

• First aid for poisoning: remove from exposure, keep the airway open, do not induce vomiting in corrosive poisoning or an unconscious person, and refer.
• Magnesium toxicity signs: loss of knee jerk, slow breathing, low urine output. Check these before each dose.
• Insulin: store unopened in a refrigerator, rotate injection sites, and watch for hypoglycaemia (sweating, shaking, confusion).
• Anaphylaxis: sudden breathlessness, swelling and low blood pressure after a drug or vaccine. Give adrenaline IM at once and refer.

Exam traps

• IM injection angle is 90 degrees, but intradermal is 10 to 15 degrees.
• Young's rule uses age ÷ (age + 12), not age ÷ 12.
• Atropine is the antidote for organophosphate poisoning, naloxone is for opioids.
• Vitamin K is the antidote for warfarin, not heparin.
• Paracetamol overdose damages the liver, but NSAIDs damage the stomach lining and kidney.
• Oxytocin is stored cold, and magnesium sulphate toxicity is reversed by calcium gluconate.
• Antibiotics do not treat viral infections.
• STAT means immediately, but SOS means when needed.
• Schedule X drugs are narcotic and psychotropic; Schedule H need a prescription.
• Generic name is the official drug name; the brand name is commercial.

One-liners

• 1. Fastest route is intravenous.
• 2. Bioavailability of IV drugs is 100%.
• 3. Paracetamol dose: 10 to 15 mg per kg.
• 4. Young's rule: age ÷ (age + 12) × adult dose.
• 5. BD means twice daily.
• 6. Atropine is the antidote for organophosphate poisoning.
• 7. Naloxone reverses opioids.
• 8. Adrenaline is the first drug in anaphylaxis.
• 9. Zinc in diarrhoea for 14 days.
• 10. Vitamin A first dose is 1 lakh IU at 9 months.
• 11. DOTS regimen includes isoniazid, rifampicin, pyrazinamide and ethambutol.
• 12. Calcium gluconate treats magnesium sulphate toxicity.

Practice questions

1. The fastest route of drug administration is:

   1. oral
   2. subcutaneous
   3. topical
   4. intravenous
   Answer

   D. intravenous

   IV drugs enter the blood directly.

2. Bioavailability of an intravenous drug is:

   1. 50%
   2. 75%
   3. 10%
   4. 100%
   Answer

   D. 100%

   The full dose reaches the circulation.

3. The angle of an intramuscular injection is:

   1. 10 to 15 degrees
   2. 45 degrees only for adults
   3. 90 degrees
   4. 20 degrees
   Answer

   C. 90 degrees

   IM is given at 90 degrees.

4. The angle of an intradermal injection is:

   1. 90 degrees
   2. 10 to 15 degrees
   3. 45 degrees
   4. 60 degrees
   Answer

   B. 10 to 15 degrees

   ID is almost parallel to the skin.

5. The abbreviation 'BD' means:

   1. three times daily
   2. once daily
   3. at bedtime
   4. twice daily
   Answer

   D. twice daily

   BD = bis die, twice a day.

6. The abbreviation 'STAT' means:

   1. at bedtime
   2. after meals
   3. when necessary
   4. immediately
   Answer

   D. immediately

   STAT means at once.

7. 'SOS' or 'PRN' in a prescription means:

   1. once daily
   2. every hour
   3. when necessary
   4. before meals
   Answer

   C. when necessary

   SOS is taken only if required.

8. The antidote for organophosphate poisoning is:

   1. atropine
   2. N-acetylcysteine
   3. vitamin K
   4. naloxone
   Answer

   A. atropine

   Atropine (with pralidoxime) is used.

9. Naloxone is the antidote for:

   1. iron overdose
   2. opioid overdose
   3. paracetamol overdose
   4. warfarin overdose
   Answer

   B. opioid overdose

   Naloxone reverses opioid effects.

10. N-acetylcysteine is used in:

    1. paracetamol overdose
    2. snake bite
    3. opioid overdose
    4. organophosphate poisoning
    Answer

    A. paracetamol overdose

    It protects the liver.

11. The antidote for warfarin overdose is:

    1. calcium gluconate
    2. vitamin K
    3. protamine
    4. atropine
    Answer

    B. vitamin K

    Vitamin K restores clotting factors.

12. The first drug to give in anaphylaxis is:

    1. paracetamol
    2. oral antihistamine only
    3. oral steroid only
    4. adrenaline intramuscularly
    Answer

    D. adrenaline intramuscularly

    Adrenaline IM is life-saving.

13. Toxicity of magnesium sulphate is reversed by:

    1. atropine
    2. glucose
    3. calcium gluconate
    4. naloxone
    Answer

    C. calcium gluconate

    Calcium gluconate is the antidote.

14. The first-line drug to prevent postpartum bleeding is:

    1. iron tablets
    2. antibiotics
    3. oxytocin
    4. paracetamol
    Answer

    C. oxytocin

    Oxytocin 10 IU IM.

15. The standard dose of vitamin A at 9 months of age is:

    1. 50,000 IU
    2. 1 lakh IU
    3. 2 lakh IU
    4. 5 lakh IU
    Answer

    B. 1 lakh IU

    1 lakh IU at 9 months, then 2 lakh IU every 6 months.

16. Zinc is given in diarrhoea for:

    1. 14 days
    2. 3 days
    3. 30 days
    4. 5 days
    Answer

    A. 14 days

    A 14-day course of zinc is advised.

17. The daily zinc dose for a child with diarrhoea above 6 months is:

    1. 5 mg
    2. 50 mg
    3. 10 mg
    4. 20 mg
    Answer

    D. 20 mg

    20 mg above 6 months, 10 mg under 6 months.

18. The drugs of the standard anti-TB regimen under DOTS include:

    1. amoxicillin and cotrimoxazole
    2. albendazole and ivermectin
    3. isoniazid, rifampicin, pyrazinamide and ethambutol
    4. chloroquine and primaquine
    Answer

    C. isoniazid, rifampicin, pyrazinamide and ethambutol

    HRZE is the intensive-phase combination.

19. Albendazole for mass deworming is given as:

    1. 400 mg single dose for older children
    2. 10 mg weekly
    3. 400 mg daily for 3 months
    4. 1 g once a year
    Answer

    A. 400 mg single dose for older children

    A single 400 mg dose.

20. Young's rule for a child's dose is:

    1. age ÷ 12 × adult dose
    2. weight ÷ 150 × adult dose
    3. age × 12 ÷ adult dose
    4. age ÷ (age + 12) × adult dose
    Answer

    D. age ÷ (age + 12) × adult dose

    Young's rule uses age ÷ (age + 12).

21. Clark's rule uses:

    1. body weight
    2. height only
    3. age in months only
    4. gender
    Answer

    A. body weight

    Child dose = weight in kg ÷ 70 × adult dose.

22. Which drug schedule is for strictly controlled narcotic and psychotropic drugs?

    1. Schedule C
    2. Schedule X
    3. Schedule A
    4. Schedule Z
    Answer

    B. Schedule X

    Schedule X drugs are strictly controlled.

23. The drug law that regulates drug manufacture and sale in India is the:

    1. PCPNDT Act, 1994
    2. Registration Act, 1969
    3. MTP Act, 1971
    4. Drugs and Cosmetics Act, 1940
    Answer

    D. Drugs and Cosmetics Act, 1940

    Drugs and Cosmetics Act, 1940.

24. A doctor orders 500 mg of a drug. Tablets contain 250 mg each. The number of tablets to give is:

    1. 1
    2. 4
    3. 0.5
    4. 2
    Answer

    D. 2

    500 ÷ 250 = 2.

25. A child needs 120 mg of paracetamol. The syrup is 125 mg per 5 ml. The volume to give is:

    1. 2.5 ml
    2. 4.8 ml
    3. 5.2 ml
    4. 6 ml
    Answer

    B. 4.8 ml

    (120 ÷ 125) × 5 = 4.8 ml.

26. A 12 kg child needs paracetamol at 15 mg per kg. The dose is:

    1. 150 mg
    2. 360 mg
    3. 180 mg
    4. 100 mg
    Answer

    C. 180 mg

    15 × 12 = 180 mg.

27. A 6-year-old child's dose by Young's rule, when the adult dose is 300 mg, is:

    1. 150 mg
    2. 50 mg
    3. 100 mg
    4. 200 mg
    Answer

    C. 100 mg

    6 ÷ 18 = 1/3; 300 ÷ 3 = 100 mg.

28. A child weighs 14 kg and the adult dose is 500 mg. Clark's rule gives a dose of:

    1. 100 mg
    2. 250 mg
    3. 140 mg
    4. 50 mg
    Answer

    A. 100 mg

    14 ÷ 70 = 1/5; 500 ÷ 5 = 100 mg.

29. A 500 ml IV fluid is to run over 4 hours using a 20 drops/ml set. The drip rate is about:

    1. 20 drops per minute
    2. 42 drops per minute
    3. 10 drops per minute
    4. 83 drops per minute
    Answer

    B. 42 drops per minute

    500 × 20 ÷ 240 = 41.7, about 42.

30. A 1% solution contains:

    1. 0.1 mg per ml
    2. 100 mg per ml
    3. 1 mg per ml
    4. 10 mg per ml
    Answer

    D. 10 mg per ml

    1% is 1 g per 100 ml = 10 mg per ml.

31. A drug is ordered 60 mg; the injection is 20 mg per ml. The volume to give is:

    1. 2 ml
    2. 3 ml
    3. 1.5 ml
    4. 6 ml
    Answer

    B. 3 ml

    60 ÷ 20 = 3 ml.

32. Match: Which pairing is correct?

    1. Anaphylaxis: naloxone
    2. Opioid overdose: atropine
    3. Eclampsia: magnesium sulphate
    4. Warfarin overdose: calcium gluconate
    Answer

    C. Eclampsia: magnesium sulphate

    MgSO4 is the anticonvulsant for eclampsia.

33. Which of the following statements is/are correct? 1. The six rights include right patient and right dose. 2. Documentation after giving a drug is not needed.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Right documentation is part of safe practice.

34. Which of the following statements is/are correct? 1. A generic name is the official drug name. 2. A brand name is the manufacturer's trade name.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

35. Which of the following statements is/are correct? 1. Antibiotics are effective against viral infections. 2. Antibiotic courses should be completed as advised.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Antibiotics do not act on viruses.

36. Which of the following statements is/are correct? 1. Paracetamol overdose can damage the liver. 2. The adult maximum dose is about 4 g per day.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

37. Which of the following statements is/are correct? 1. Oxytocin and vaccines are kept in the cold chain. 2. Controlled drugs should be kept locked.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

38. Which of the following statements is/are correct? 1. Pharmacokinetics is what the body does to the drug. 2. Pharmacodynamics is what the drug does to the body.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

39. Which of the following statements is/are correct? 1. Tolerance is the need for larger doses over time to get the same effect. 2. Allergy is the same as a toxic effect due to overdose.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Allergy is an immune reaction, not overdose toxicity.

40. Which of the following statements is/are correct? 1. Methyldopa is considered safe for hypertension in pregnancy. 2. ORS is not needed when zinc is given.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    ORS is the key treatment in diarrhoea.

41. Which of the following statements is/are correct? 1. The sublingual route avoids the first pass through the liver. 2. Intravenous drugs have 100% bioavailability.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

42. Which is a side effect of iron tablets?

    1. Blue urine only
    2. Hair gain
    3. Black stools
    4. Fever with rash always
    Answer

    C. Black stools

    Black stools are a harmless effect of iron.

43. Which injection site is recommended in infants for IM injection?

    1. Gluteal region
    2. Deltoid only
    3. Abdomen
    4. Vastus lateralis (outer thigh)
    Answer

    D. Vastus lateralis (outer thigh)

    The thigh is safe in infants.