Duromine (Phentermine) Classification in Australia

Phentermine (Duromine) is classified as a Schedule IV controlled substance, not an S4D medication in Australia. 1

Understanding Phentermine's Classification

Phentermine is a sympathomimetic amine anorectic medication that acts as an adrenergic agonist, promoting weight loss by activating the sympathetic nervous system 2
It is approved for short-term use (typically 12 weeks) for weight management in obesity 2
Phentermine is chemically and pharmacologically related to amphetamines, which is why it's classified as a controlled substance 1
As a Schedule IV medication, it has recognized potential for abuse and dependence, though lower than Schedule II or III substances 1

Phentermine is available in various formulations including capsules (15 mg, 30 mg, 37.5 mg) and tablets (8 mg, 37.5 mg) 2
Despite being approved only for short-term use, many clinicians prescribe phentermine for longer durations as off-label therapy for continued weight management 2
Prescribers should be aware of local laws and regulations regarding prescribing controlled substances 2
If using phentermine long-term (beyond 12 weeks), documentation of specific benefits, tolerance, and adverse effects is recommended 2

Common side effects include dry mouth, insomnia, dizziness, irritability, constipation, and headache 2
Phentermine should be avoided in patients with:
- Cardiovascular disease or uncontrolled hypertension 2
- History of drug abuse 2
- Glaucoma or hyperthyroidism 2
- During or within 14 days of taking monoamine oxidase inhibitors (MAOIs) 2
- Pregnancy (Category X) 1
Blood pressure and heart rate should be monitored periodically during treatment 2
Phentermine has potential for drug-drug interactions, particularly with other sympathomimetic amines and certain antidepressants 3

When combined with lifestyle interventions, phentermine can achieve approximately 5-10% body weight loss in successful patients 2
In clinical trials, phentermine (15 mg daily) was associated with 6.0 kg weight loss at 28 weeks compared to placebo 2
About 46% of subjects achieved ≥5% weight loss and 20.8% achieved ≥10% weight loss with phentermine, compared to 15.5% and 6.8% with placebo, respectively 2

While phentermine is a controlled substance due to its chemical similarity to amphetamines, studies examining abrupt cessation have not demonstrated typical withdrawal symptoms seen with amphetamine dependence 4
The primary concerns with long-term use relate to cardiovascular effects rather than addiction potential 2
Phentermine should be distinguished from the previously available "fen-phen" combination (phentermine with fenfluramine), which was associated with valvular heart disease and pulmonary hypertension 2