Lecture Notes Video: Dosage Calculations and Antipsychotics (Vocabulary Flashcards)

Dosage Calculations: Basics and Rules

• Topic context: Basic and simple dosage calculations discussed in class; aim is accurate dosing through math and unit conversions.
• Key workflow mentioned: identify the required dose, know the stock concentration or tablet strength, compute the admin quantity (volume or number of tablets), and verify units.
• Common student interactions referenced:
  • Students asking to confirm understanding and to review homework.
  • Proctored exam context and reviewing notes during class.
  • Emphasis on participation and note-taking during reviews.

Core concepts introduced in the transcript

• Simple dosage calculations are a foundational skill for patient safety.
• The core rule for unit conversion is described verbally as:
  • When converting from a smaller unit to a larger unit, divide.
  • When converting from a larger unit to a smaller unit, multiply.
• Practical phrasing observed: "it’s small to big, it’s divide; big to small, you tell (multiply)." This aligns with common dimensional analysis rules used in pharmacology.
• There is an emphasis on explicit steps and showing work, especially in a proctored setting.

Unit Conversions and the Small-to-Big vs Big-to-Small Rule

• What the rule means in practice:
  • Converting to a larger unit (e.g., mg to g): divide by the conversion factor.
  • Converting to a smaller unit (e.g., g to mg): multiply by the conversion factor.
• Common conversion examples to memorize:
  • 1\ \text{g} = 1000\ \text{mg}
  • 1\ \text{mg} = 1000\ \mu\text{g}
  • 1\ \text{L} = 1000\ \text{mL}
• How this applies to dose calculations:
  • If the desired dose is given in mg and the stock is in mg/mL, the volume to administer is:
  • V = \dfrac{D}{C} where:
  • D = desired dose (mg),
  • C = stock concentration (mg/mL),
  • V = volume to administer (mL).
  • If dosing by tablets, the number of tablets is:
  • N = \dfrac{D}{D{\text{per tablet}}} where D{\text{per tablet}} is the strength per tablet.
• Worked example:
  • Example 1: Need D = 75\ \text{mg}; stock concentration C = 25\ \text{mg/mL}.
  • V = \dfrac{75}{25} = 3\ \text{mL}.
  • Example 2: Convert to larger unit: 1.5\ \text{g} = 1500\ \text{mg} (divide? or multiply depending on direction; here converting g to mg uses big-to-small, i.e., multiply by 1000).
  • Example 3: Dose by tablets: if each tablet is 0.5 mg and the prescribed dose is 2 mg:
  • N = \dfrac{2}{0.5} = 4 tablets.
• Practical reminder: always include units in every step and cancel units as you go to avoid errors.

Worked Practice Scenarios (Illustrative Examples)

• Scenario A: Volume from concentration
  • Stock: C = 10\ \text{mg/mL}
  • Desired dose: D = 45\ \text{mg}
  • Compute volume: V = \dfrac{D}{C} = \dfrac{45}{10} = 4.5\ \text{mL}
• Scenario B: Unit conversion from g to mg
  • Dose in grams: D_g = 1.25\ \text{g}
  • Convert to mg: D{mg} = Dg \times 1000 = 1.25 \times 1000 = 1250\ \text{mg}
• Scenario C: Tablet-based dosing
  • Prescribed dose: D = 7\ \text{mg}
  • Tablet strength: D_{\text{per tablet}} = 2\ \text{mg}
  • Tablets to administer: N = \dfrac{7}{2} = 3.5\text{ tablets} (rounding considerations apply; typically round to feasible administration and consult prescriber as needed)
• Important caveat (safety): when calculations yield nonstandard numbers (like 3.5 tablets), confirm rounding policy and check if a liquid form or alternative strength is available.

Proctored Exam Context and Study Habits

• The transcript suggests a proctored session with live review and notes taking.
• Key exam strategies implied:
  • Bring and refer to written material during review, but rely on showing your calculation steps.
  • Engage with classmates to reinforce understanding; participate to maximize comprehension.
  • Have a clear method for performing calculations and check your work before submission.
• Practical tips for dosage calculation exams:
  • Write down the given data clearly (target dose, stock strength, units).
  • Cancel units step by step to ensure dimensional consistency.
  • Use the smallest number of steps that keeps units clear to reduce error.

Antipsychotics: Major (Overview and Context)

• From the transcript: a topic tag/section appears: "Antipsychotides. Major." This likely indicates a forthcoming discussion on major antipsychotic medications.
• General pharmacology context (relevant to the course):
  • Antipsychotics are used to treat psychotic disorders (e.g., schizophrenia, bipolar disorder with psychotic features).
  • Major (typical) antipsychotics include drugs like haloperidol and chlorpromazine; they primarily block dopamine D2 receptors.
  • Atypical (second-generation) antipsychotics include drugs like risperidone, olanzapine, quetiapine; they block dopamine and serotonin receptors with a different side effect profile.
  • Common considerations in dosing include starting doses, titration, monitoring for extrapyramidal symptoms (EPS), tardive dyskinesia, metabolic effects, and patient-specific factors (age, comorbidities, renal/hepatic function).
• Significance for dosage calculations:
  • Some antipsychotic regimens require precise dosing and careful unit conversions when calculating oral suspensions, tablet counts, or liquid forms.
  • Exam-style questions may test the ability to compute doses from stock solutions or to determine the number of tablets to dispense.
• Example topics to review (general, not from transcript):
  • Typical vs atypical antipsychotics differences
  • Common starting doses and target maintenance doses (drug-specific)
  • Monitoring parameters and safety considerations

Connections to Foundational Principles and Real-World Relevance

• Foundational principle: dimensional analysis and unit consistency underpin safe pharmacology practice.
• Real-world relevance: accurate dosage calculations directly affect patient safety and therapeutic effectiveness; errors can lead to underdosing or overdosing with potentially serious consequences.
• Relationship to pharmacokinetics/pharmacodynamics: dosing decisions are influenced by absorption, distribution, metabolism, and excretion factors, which determine how much drug to give and how often.
• Practical relevance to clinical workflows: tablets vs liquid forms, concentration changes, and dose rounding rules are everyday considerations in healthcare settings.

Ethical and Practical Implications

• Responsibility to verify calculations and seek clarification when data are unclear or ambiguous.
• Safety-first mindset: when numbers don’t align or a dose requires nonstandard quantities (e.g., half tablets), consult prescribers or use alternative formulations when available.
• Documentation and transparency: document all steps taken during calculations to facilitate review and reduce miscommunication.
• Respect for patient-specific needs: dosing must be individualized considering weight, age, organ function, and comorbidities; avoid one-size-fits-all approaches.

Summary of Key Formulas and Rules (LaTeX)

• Volume from concentration (mg/mL):
  • V = \dfrac{D}{C}
• Tablet-based dosing:
  • N = \dfrac{D}{D_{\text{per tablet}}}
• Unit conversions (examples):
  • 1\ \text{g} = 1000\ \text{mg}
  • 1\ \text{mg} = 1000\ \mu\text{g}
  • 1\ \text{L} = 1000\ \text{mL}
• Examples (worked):
  • If D=75\ \text{mg} and C=25\ \text{mg/mL}, then V = \dfrac{75}{25} = 3\ \text{mL}.
  • If converting to mg from g: D{mg} = Dg \times 1000.
  • If dosing 2 mg with a tablet of 0.5 mg: N = \dfrac{2}{0.5} = 4\text{ tablets}.

Note: The transcript captures a focus on basic dosage calculations, the rule for unit conversion (small-to-big divide; big-to-small multiply), and mentions of proctored sessions and a section on antipsychotics. The notes above synthesize those ideas into a structured study guide with concrete formulas and examples to help you study effectively.