LIPO-6 according to its manufacturer Nutrex Research, Inc. is a fat-loss formula that includes Synephrine HCL (20 mg), Synthetic 99% Guggolsterones Z&E 1:1 (20 mg), Yohimbine HCL (3 mg), Caffeine Anhydrous USP (200 mg) and Bioperine.

Nutrex claims that LIPO-6 acts immediately by targeting stored body fat, controlling appetite and speeding metabolism. Nutrex also claims that its products are pharmaceutical strength with more efficient absorption compared to lesser refined herbal products.

Two main issues concerned are ...
Is it safe?
Does it work (is it effective)?

SAFETY
Synephrine (Seville orange or Citrus Aurantium extracts) have been marketed as a safe alternative to banned ephedra. Synephrine (also known as oxedrine) is similar in structure to epinephrine. Epinephrine is known to help with lipolysis.

An extensive search of MEDLINE, EMBASE, BIOSIS, and the Cochrane Collaboration Database identified only 1 eligible randomized placebo controlled trial, which followed 20 patients for 6 weeks, demonstrated no statistically significant benefit for weight loss. Other studies have reported increased metabolic rates during ingestion of Citrus aurantium and another study showed a mean fat mass loss of 2.4 kg (5.28 LBS) among 9 women during a second week of study that involved Citrus aurantium ingestion.

The RECOMMENDED USE section clearly states that consumers should not exceed dosage.

The WARNING section clearly states that consumers should not combine the product with other products, over-the-counter products or foods and beverages that might contain the same or similar ingredients (coffee, tea, soda, other dietary supplements, medications containing phenylephrine). Nutrex also warns that a physician should also be consulted for any of the following situations:

Medication use, including, but not limited to, MAOI inhibitors, antidepressants, aspirin, non-steroidal anti-inflammatory drugs or products containing phenylephrine, epedrine, pseudoephedrine, or other stimulants.

Medical Conditions, including, but not limited to, heart, liver, kidney, or thyroid disease, psychiatric diorders, difficulty urinating, diabetes, high blood pressure (hypertension), cardiac arrhythmia, recurrent headaches, enlarged prostate or glaucoma.
 
Product avoidance:
Pregnant or nursing females should NOT use this product.

Upcoming surgery should be preceded by cessation of product use 2 weeks prior to surgery.

Symptoms of rapid heart beat, dizziness, severe headaches or shortness of breath should signal immediate cessation of product use.

SAFETY SUMMARY
Most people will not have safety issues with LIPO-6 if they follow directions and are very careful to restrict other similar products. However, some individuals are unpredictably sensitive to certain ingredients. Sensitive individuals may develop or exacerbate hypertension of cardiorespiratory products.


EFFECTIVENESS or EFFICACY
A study in the British Journal of Clinical Pharmacology in March 2008 reported that a performance-enhancing supplement with 21 mg of Synephrine modestly improved exercise tolerance in a study of ten healthy individuals. Exercise was perceived as less strenuous after consumption. Blood pressure and plasma glucose increased post-exercise with supplement use, which could be detrimental in some people.

More info ...
Lipo6.com

References:
Haller CA, Duan M, Jacob P 3rd, Benowitz N. Human pharmacology of a performance-enhancing dietary supplement under resting and exercise conditions.
Br J Clin Pharmacol. 2008 Mar 13. [Epub ahead of print]
PMID: 18341680

Preuss HG, DiFerdinando D, Bagchi M, Bagchi D. Citrus aurantium as a thermogenic, weight-reduction replacement for ephedra: an overview. J Med. 2002;33(1-4):247-64.