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HLT-LPN37-02 · Lesson 9 · 18 clock hours · theory

Drug Classifications Part 2: Anti-infectives, Endocrine, Gastrointestinal, and Psychiatric Agents

Objective. The student will describe the mechanism of action, therapeutic uses, major adverse effects, contraindications, and LPN nursing implications for anti-infective, endocrine, gastrointestinal, and psychiatric drug classes.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

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Drug Classifications Part 2: Anti-infectives, Endocrine, Gastrointestinal, and Psychiatric Agents

Understanding how drugs work — and how to give them safely — is a core LPN competency. This lesson covers four major drug categories tested on the NCLEX-PN and encountered daily in clinical practice.

Anti-infective Agents

Penicillins (e.g., amoxicillin, ampicillin) work by interfering with bacterial cell-wall synthesis, causing the organism to burst and die. They are used for respiratory, skin, and urinary tract infections. The most important nursing concern is allergy: always ask about penicillin allergy before administration. Anaphylaxis, though rare, is life-threatening. Cross-sensitivity with cephalosporins exists in a small percentage of patients; report any prior reaction to the provider.

Cephalosporins (e.g., cephalexin, ceftriaxone) share the cell-wall mechanism and have broad-spectrum coverage across four generations. Adverse effects include GI upset and, rarely, severe hypersensitivity. Monitor patients with known penicillin allergy closely.

Fluoroquinolones (e.g., ciprofloxacin, levofloxacin) inhibit bacterial DNA replication enzymes. They carry a black-box warning for tendinitis, tendon rupture, and peripheral neuropathy. Do not give with antacids containing magnesium or aluminum — they bind the drug and reduce absorption. Avoid in children and pregnant patients unless specifically ordered.

Antifungals (e.g., fluconazole, nystatin) target the fungal cell membrane. Nystatin is used topically or orally for oral or vaginal candidiasis. Systemic antifungals such as fluconazole can cause liver toxicity; monitor liver function tests as ordered and teach patients to report jaundice.

Endocrine Agents

Insulin replaces or supplements the body's own insulin for patients with diabetes. The LPN must know the four types:

Insulin safety rule — draw clear before cloudy: When mixing regular (clear) and NPH (cloudy) in one syringe, always draw up regular insulin first to avoid contaminating the regular vial with NPH. Always verify the dose with a second nurse per facility policy. The primary adverse effect is hypoglycemia (blood glucose typically below 70 mg/dL). Signs include shakiness, diaphoresis, confusion, and pallor. Emergency response: administer fast-acting carbohydrate (e.g., glucose tablets or juice) if the patient is conscious and able to swallow; follow facility protocol and notify the provider.

Oral antidiabetics include metformin (first-line for type 2 diabetes; decreases hepatic glucose production; hold before contrast dye procedures), sulfonylureas (stimulate insulin release; hypoglycemia risk), and others. Teach patients to monitor blood glucose and recognize hypoglycemia signs.

Thyroid agents: Levothyroxine replaces thyroid hormone in hypothyroidism. Give on an empty stomach in the morning. Signs of too much (toxicity): tachycardia, palpitations, weight loss, heat intolerance. Signs of too little: fatigue, cold intolerance. Propylthiouracil (PTU) and methimazole suppress thyroid hormone production in hyperthyroidism; monitor for agranulocytosis (sore throat, fever — instruct patient to report immediately).

Gastrointestinal Agents

Antiemetics (e.g., ondansetron, promethazine) relieve nausea and vomiting. Promethazine carries a black-box warning against IV use in children and for subcutaneous injection due to severe tissue injury risk; give IV promethazine only per facility policy and with extreme caution. Ondansetron is generally well tolerated; monitor for prolonged QT interval.

Antacids (e.g., calcium carbonate, magnesium hydroxide) neutralize stomach acid for heartburn and peptic ulcer symptoms. They can interact with many drugs by altering absorption — give other oral medications 1–2 hours before or after antacids. Magnesium-containing antacids may cause diarrhea; aluminum-containing antacids may cause constipation.

Psychiatric Agents

SSRIs (selective serotonin reuptake inhibitors, e.g., sertraline, fluoxetine) are first-line antidepressants that block reuptake of serotonin, increasing its availability in the synapse. Adverse effects include GI upset, sexual dysfunction, and insomnia. A critical black-box warning exists for increased risk of suicidal thinking in children, adolescents, and young adults — monitor closely, especially in the first weeks of therapy. Serotonin syndrome (agitation, hyperthermia, muscle rigidity, rapid heart rate) is a rare but dangerous toxicity, especially when combined with other serotonergic drugs.

Antipsychotics: Older (typical) agents such as haloperidol block dopamine receptors. Newer (atypical) agents such as risperidone and olanzapine have broader receptor activity. Key adverse effects include extrapyramidal symptoms (EPS: tremor, rigidity, restlessness), tardive dyskinesia (involuntary movements after long-term use), and neuroleptic malignant syndrome (NMS: high fever, muscle rigidity, altered consciousness — a medical emergency). Metabolic effects (weight gain, hyperglycemia) are especially common with atypical antipsychotics. Always assess for EPS at each contact.

LPN Scope of Practice Reminders

The LPN administers medications under the supervision of an RN or provider. Always check the five rights (right patient, drug, dose, route, time) plus right documentation. Use a current drug reference — a black-box warning you did not know about can harm or kill a patient. Never hesitate to clarify an order before giving any medication.

Key terms8

Black-box warningThe FDA's strongest drug warning, placed in a prominent box in the prescribing information to alert clinicians to serious or life-threatening risks associated with the medication.
HypoglycemiaA condition in which blood glucose falls below normal (typically below 70 mg/dL), causing symptoms such as shakiness, diaphoresis, confusion, and, if untreated, loss of consciousness.
Extrapyramidal symptoms (EPS)Movement disorders caused by dopamine-blocking drugs, including tremor, muscle rigidity, restlessness (akathisia), and acute muscle spasms (dystonia).
Serotonin syndromeA potentially life-threatening drug reaction resulting from excess serotonergic activity, characterized by agitation, hyperthermia, muscle rigidity, and autonomic instability.
Neuroleptic malignant syndrome (NMS)A rare but life-threatening reaction to antipsychotic medications, presenting with high fever, severe muscle rigidity, altered consciousness, and autonomic instability.
Cross-sensitivityA phenomenon in which a patient allergic to one drug also reacts to a structurally related drug, as can occur between penicillins and cephalosporins.
Basal insulinLong-acting insulin that provides a steady, low-level background effect over 24 hours or more, mimicking the body's continuous baseline insulin secretion.
Tardive dyskinesiaA potentially irreversible movement disorder characterized by repetitive, involuntary movements (commonly of the face and tongue) that can develop after prolonged use of antipsychotic medications.

Worked examples3

1. A patient is prescribed 10 units of regular insulin and 20 units of NPH insulin to be mixed in one syringe. Describe the correct order of preparation and state the final volume you will draw up if using a U-100 insulin syringe.
  1. Step 1 — Gather supplies: one insulin syringe, the regular insulin vial (clear), and the NPH vial (cloudy). Verify both vials with a second nurse per facility policy.
  2. Step 2 — Inject air into the NPH vial first: draw 20 units of air into the syringe and inject it into the NPH vial without drawing any insulin yet; withdraw the needle.
  3. Step 3 — Inject air into the regular vial: draw 10 units of air and inject into the regular (clear) vial.
  4. Step 4 — Draw clear first: invert the regular vial and withdraw exactly 10 units of regular insulin.
  5. Step 5 — Draw cloudy second: invert the NPH vial and withdraw 20 units of NPH insulin, bringing the total in the syringe to 30 units.
  6. Step 6 — Verify the combined dose (30 units) with the second nurse before administration.
Answer: Total volume to administer: 30 units (10 units regular + 20 units NPH) in one syringe; drawn clear before cloudy to prevent contamination of the regular insulin vial.
2. A patient on metformin is scheduled for a CT scan with IV contrast dye tomorrow morning. The patient asks if they should take their metformin as usual. What is the correct nursing response and rationale?
  1. Step 1 — Recall the pharmacology: metformin is held before procedures using iodinated contrast dye because contrast can temporarily impair kidney function, causing metformin to accumulate and increase the risk of lactic acidosis.
  2. Step 2 — Recognize scope: the LPN should not independently decide to withhold or continue a medication; clarify the order with the provider or RN supervisor.
  3. Step 3 — Communicate findings: inform the charge nurse or provider that the patient is on metformin and is scheduled for contrast imaging, so the provider can issue a specific hold or continuation order per current facility and radiological guidelines.
Answer: Do not advise the patient independently. Notify the provider or supervising nurse immediately so a hold order can be issued if appropriate, consistent with current guidelines and the patient's kidney function.
3. A patient taking sertraline reports feeling extremely agitated, has a temperature of 103 °F, muscle rigidity, and a heart rate of 118 bpm after a new medication was added to their regimen. What condition should the LPN suspect, and what is the immediate nursing action?
  1. Step 1 — Recognize the cluster of symptoms: agitation, hyperthermia, muscle rigidity, and tachycardia in a patient on an SSRI after a new drug is added is a classic presentation of serotonin syndrome.
  2. Step 2 — Prioritize patient safety: do not leave the patient alone; call for the charge nurse or provider immediately.
  3. Step 3 — Prepare to follow emergency orders: anticipate that the provider may discontinue the offending agent(s) and order supportive care. Document findings accurately and report in a timely manner.
Answer: Suspect serotonin syndrome. The immediate action is to stay with the patient, call for the charge nurse and provider without delay, and be prepared to implement emergency orders. This is a medical emergency.
In class: Students complete a drug-classification grid for antibiotics (penicillins, cephalosporins, fluoroquinolones), antifungals, insulin types (rapid, short, intermediate, long-acting), oral antidiabetics, thyroid agents, antiemetics, antacids, SSRIs, and antipsychotics. · Insulin safety station: students correctly draw up and mix two types of simulated insulin (draw clear before cloudy), verify dose with a simulated peer nurse, and identify hypoglycemia signs and the nurse's emergency response. · Students use a current drug reference to look up three unfamiliar medications from the list, locate black-box warnings, and present findings to the class, emphasizing why the LPN must know where to find reliable drug information during practice.
Materials: Pharmacology textbook; drug-classification grid worksheet; insulin syringes; simulated insulin vials (NPH and regular placebo); current drug handbook; black-box warning handout
Check: Drug classification quiz covering 30 drugs across the four categories; student must score 80% or higher to proceed.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Pharmacological and Parenteral Therapies
1. A patient is prescribed ciprofloxacin for a urinary tract infection. Which instruction is most important for the LPN to include in patient teaching?
Pharmacological and Parenteral Therapies
2. The LPN is preparing to mix regular insulin and NPH insulin in one syringe. Which action reflects correct technique?
Pharmacological and Parenteral Therapies
3. A patient receiving haloperidol develops sudden severe muscle stiffness of the neck and jaw, and an inability to open the mouth. The LPN recognizes this as which adverse effect?
Pharmacological and Parenteral Therapies
4. A patient on levothyroxine calls to report heart palpitations, significant weight loss over four weeks, and feeling uncomfortably warm all the time. The LPN should recognize these as signs of which condition?
Psychosocial Integrity
5. Which finding in a patient taking an SSRI for depression requires the most immediate action by the LPN?
Pharmacological and Parenteral Therapies
6. A patient with type 2 diabetes is prescribed glargine insulin once daily. The patient asks if they can mix glargine in the same syringe as their morning NPH insulin to reduce injections. What is the correct LPN response?
Pharmacological and Parenteral Therapies
7. A patient taking methimazole for hyperthyroidism calls to report a sudden sore throat and fever. The LPN's priority action is to:
Pharmacological and Parenteral Therapies
8. The LPN is caring for a patient who received ondansetron for nausea. Which assessment finding would be most important to report to the supervising nurse?
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