From the Guidelines
Clonidine at a dose of 100 micrograms can produce significant effects, including a reduction in blood pressure, sedation, dry mouth, and potential analgesic effects, as it acts on alpha-2 adrenergic receptors in the brain. This medication is generally reserved as last-line due to significant CNS adverse effects, especially in older adults, as noted in the guidelines by the American College of Cardiology and American Heart Association 1. The usual dose range for clonidine oral is 0.1–0.8 mg/day, with a daily frequency of 2, indicating that 100 micrograms (or 0.1 mg) is at the lower end of the therapeutic range 1.
Key effects and considerations of clonidine at this dose include:
- Reduction in blood pressure by decreasing sympathetic outflow from the central nervous system, with noticeable drops in both systolic and diastolic readings occurring within 30-60 minutes after oral administration.
- Sedation, making some patients feel drowsy or fatigued.
- Dry mouth due to the drug's anticholinergic properties.
- Potential to reduce anxiety, decrease withdrawal symptoms in those dependent on opioids or alcohol, and provide some analgesic effects.
- Risk of dizziness when standing up quickly due to orthostatic hypotension.
- Effects typically last 6-8 hours, though blood pressure effects may persist longer.
It's crucial to monitor for potential adverse effects, especially in populations at risk, and to taper the medication rather than discontinuing it abruptly to avoid rebound hypertension, as advised in guidelines and studies 1. The medication works by stimulating alpha-2 receptors, inhibiting the release of norepinephrine, and ultimately dampening sympathetic nervous system activity throughout the body. Given the potential for significant CNS adverse effects, clonidine is generally used when the benefits outweigh the risks, particularly in cases of hypertension, ADHD, menopausal symptoms, or as an adjunct for pain management.
From the Research
Effects of 100 Micrograms of Clonidine
- The effects of 100 micrograms of clonidine were studied in patients with severe, intractable cancer pain 2.
- Clonidine produced analgesia, as measured by change in verbal pain scores, lasting more than 6 hours 2.
- Clonidine also decreased blood pressure, although this effect was well tolerated and no patient met criteria for receiving iv ephedrine 2.
- Clonidine decreased heart rate 10-30% and produced transient sedation 2.
- Serum glucose and cortisol and oxyhemoglobin saturation were not altered by clonidine 2.
Comparison with Other Doses
- A study compared the effects of clonidine at doses ranging from 3.1 to 25.7 micrograms/kg in patients with essential hypertension 3.
- The study found that the observed blood pressure effects could be dissociated into depressor and pressor components, and a window for the anti-hypertensive effect was established 3.
- However, the study did not specifically examine the effects of 100 micrograms of clonidine.
Other Effects of Clonidine
- Clonidine has been used off-label in children and adolescents with attention deficit and hyperactivity disorders (ADHD) with or without comorbidities 4.
- Clonidine extended-release was recently approved by the US Food and Drug Administration for ADHD in children 4.
- Clonidine has been shown to be effective in reducing exercise-induced increases in blood pressure and electrocardiographic ischemic changes in patients with coronary heart disease 5.
- Clonidine has also been shown to produce a decrease in total systemic resistance and a reduction in left ventricular stroke work index in patients with acute myocardial infarction complicated by hypertension 6.