Phentermine Overview and Guidelines

Drug Class

• Phentermine is classified as an amphetamine and an anti-obesity agent.

Route of Administration

• Administered orally, either as tablets, capsules, or disintegrating tablets.

Dosing Information

• Recommended dosage varies:
  • Tablets: 37.5 mg once daily before or 1-2 hours after breakfast; some may need only 18.75 mg daily or split doses.
  • Capsules: 15-30 mg daily, taken 2 hours after breakfast.
  • Disintegrating tablets: 15-30 mg dissolved on the tongue in the morning with or without food.
• Discontinue if tolerance develops; do not exceed recommended doses.

Administration Guidelines

• Tablets: Take before breakfast or 1-2 hours after.
• Capsules: Take 2 hours after breakfast.
• Disintegrating tablets: Must be placed on the tongue to dissolve and can be taken with or without water.
• Avoid administration in the late evening to prevent insomnia.

Contraindications

• Should not be taken by individuals with:
  • Agitated states
  • Cardiovascular diseases
  • History of drug abuse
  • Glaucoma
  • Hyperthyroidism
  • Hypersensitivity to sympathomimetics
  • Pregnant or nursing women

Precautions

• Avoid combination with other weight loss drugs or SSRIs.
• Monitor diabetes patients as insulin requirements may decrease.
• Report any symptoms of primary pulmonary hypertension.
• Sensitivity to tartrazine (FD&C Yellow No. 5) may occur, particularly with aspirin sensitivity.

Adverse Effects

• Common side effects include:
  • Xerostomia (dry mouth)
  • Nervousness, insomnia, irritability
• Serious potential effects encompass:
  • Cardiomyopathy, heart valve disorders
  • Cerebral hemorrhage, ischemia
  • Psychotic disorders, and primary pulmonary hypertension

Drug Interactions

• Significant interactions with:
  • Isoproterenol, dopamine, ephedrine, epinephrine, norepinephrine
  • Linezolid, phenylephrine, venlafaxine
• May interact with other stimulants and medications for obesity.

Monitoring Requirements

• Track weight reduction as an indicator of medication effectiveness.
• Assess renal function, especially in elderly patients or those with renal impairment.

Mechanism of Action

• Phentermine functions as a sympathomimetic amine, stimulating the central nervous system and potentially increasing blood pressure.
• Exact actions related to obesity treatment remain unclear.

Pharmacokinetics

• Absorption properties show a Tmax of 3 to 4.4 hours for orally disintegrating tablets.
• Food can slightly decrease Cmax and AUC.
• Renal excretion is significant, with 62 to 85% excreted unchanged.

Medication Counseling

• Advise against taking phentermine during or within 14 days post-MAO inhibitor use.
• Caution advised regarding activities requiring mental alertness.
• Common side effects include dry mouth, gastrointestinal issues, headache, insomnia, and possible changes in libido.
• Encourage reporting of any declining exercise tolerance or significant side effects.

This quiz covers the classification, administration, and dosing information for Phentermine, an anti-obesity medication. It outlines the recommended dosages for various forms and provides important guidelines for safe administration. Additionally, the quiz highlights contraindications for users.