Skull Labs Ripper 60 caps

Caffeine

Caffeine is a stimulant that blocks adenosine receptors in the brain, reducing perceived effort and fatigue. It is found in coffee, tea and energy drinks and is a common ingredient in pre-workout products¹.

Dicaffeine malate (sold as Infinergy®) is caffeine bonded to malic acid. Its caffeine adds to the total caffeine in a product, but labels do not always state the caffeine equivalent.

Synephrine (bitter orange, Citrus aurantium)

p-Synephrine is the main protoalkaloid of bitter orange (Citrus aurantium). It is structurally related to adrenaline and is used in weight-loss and pre-workout products².

White willow bark (salicin)

White willow bark contains salicin, a natural precursor of salicylic acid, chemically related to aspirin. Some stimulant products also contain aspirin itself.

DMAA (1,3-dimethylamylamine)

DMAA (1,3-dimethylamylamine, methylhexanamine) is a synthetic stimulant that constricts blood vessels and raises blood pressure. It has been sold in pre-workout and weight-loss supplements and as a recreational stimulant³.

Hordenine

Hordenine (N,N-dimethyltyramine) is a phenethylamine alkaloid found in barley and beer. It acts on the dopamine D2 receptor and is marketed in pre-workout and fat-burning products⁴.

Octopamine and halostachine

Octopamine and halostachine (N-methylphenylethanolamine) are phenethylamine-type amines related to synephrine and adrenaline. They appear in weight-loss and pre-workout products⁵.

Higenamine

Higenamine is a plant alkaloid that stimulates β2-adrenergic receptors, the same receptor family targeted by asthma bronchodilators. It is found in plants such as Nandina domestica⁶.

Yohimbine (yohimbe bark, rauwolscine)

Yohimbine is an alkaloid from the bark of the African tree Pausinystalia yohimbe. It blocks α2-adrenergic receptors, which increases noradrenaline release. Rauwolscine (alpha-yohimbine) is a closely related alkaloid.

Huperzine A

Huperzine A is an alkaloid from the club moss Huperzia serrata. It inhibits acetylcholinesterase, the enzyme that breaks down the neurotransmitter acetylcholine, and it has been used as a medicine for dementia in China⁷.

Caffeine

The International Society of Sports Nutrition concludes that caffeine consistently improves exercise performance when consumed in doses of about 3–6 mg per kg of body mass, with benefits for muscular endurance, movement velocity, strength, sprinting, jumping and aerobic exercise¹.

Synephrine (bitter orange, Citrus aurantium)

A review of human clinical studies reported small increases in energy expenditure and modest weight loss with bitter orange extract or p-synephrine products over 6–12 weeks, many in combination with other ingredients².

White willow bark (salicin)

A review found evidence of pain-relieving effects of willow bark extracts, with fewer adverse effects than non-steroidal anti-inflammatory drugs including aspirin⁸.

DMAA (1,3-dimethylamylamine)

No controlled trials show that DMAA improves athletic performance or weight loss. A pharmacokinetic study of a single 25 mg dose did not find meaningful changes in resting heart rate, blood pressure or body temperature⁹.

Hordenine

There are no controlled human trials of hordenine for exercise performance or weight loss. Human research concerns its absorption from beer, where plasma levels were too low for a direct effect on dopamine receptors⁴.

Octopamine and halostachine

There are no controlled human trials showing benefits for weight loss or performance. Research concerns their detection and quantification in sports supplements⁵¹⁰.

Higenamine

There are no controlled human trials showing that higenamine improves exercise performance or weight loss. Analyses of US supplements found up to about 62 mg per serving, with labels that often did not state the amount⁶.

Yohimbine (yohimbe bark, rauwolscine)

A small trial in professional soccer players found reduced body fat with yohimbine but no change in body mass, muscle mass or performance¹¹. Larger, independent trials are lacking.

Huperzine A

A Cochrane review found some benefit on cognitive function in people with Alzheimer's disease, but only one study was of adequate quality and size, so there was inadequate evidence to recommend its use⁷. A Cochrane review in mild cognitive impairment found the evidence insufficient¹².

There is no good evidence that huperzine A improves focus or performance in healthy people.

Caffeine

Responses vary widely between people, partly because of genetics and habitual caffeine use. Many studies use pure caffeine, so results do not automatically apply to multi-ingredient products¹.

Synephrine (bitter orange, Citrus aurantium)

Most studies are small, short and use multi-ingredient products, and longer studies are needed to establish efficacy and safety².

White willow bark (salicin)

Trials are few and use different extracts⁸.

DMAA (1,3-dimethylamylamine)

The single-dose study does not reflect repeated use, higher doses or combination with other stimulants and exercise⁹. Analyses of sports and weight-loss supplements have repeatedly found stimulants that were not declared, or quantities different from the label¹³¹⁴.

Hordenine

Supplement amounts are much higher than the amounts studied from beer, and their effects have not been studied⁴.

Octopamine and halostachine

Without human trials, effects and safe amounts are unknown. Analyses of sports and weight-loss supplements have repeatedly found stimulants that were not declared, or quantities different from the label¹³¹⁴.

Higenamine

Published research concerns supplement analysis rather than effects in humans⁶.

Yohimbine (yohimbe bark, rauwolscine)

Evidence for fat loss or performance is limited to small studies. Supplement labels are often inaccurate: of 49 US yohimbine supplements tested, only 2 gave accurate information on both the quantity and the known adverse effects¹⁵.

Huperzine A

The trials are mostly small, of limited quality and in people with cognitive disease, so they do not apply to healthy users⁷¹².

Caffeine

EFSA concluded that single doses of up to 200 mg, and daily intakes of up to 400 mg from all sources, do not raise safety concerns for healthy adults. For pregnant and breastfeeding women, daily intakes up to 200 mg do not raise concerns for the foetus or infant¹⁶.

Higher intakes can cause anxiety, sleep disturbance, raised heart rate and blood pressure, and digestive upset. Combining several caffeine sources (coffee, energy drinks, pre-workouts) raises total intake¹⁶¹.

Synephrine (bitter orange, Citrus aurantium)

The reviewed studies did not report serious adverse effects at the doses tested², but combining synephrine with caffeine and other stimulants increases cardiovascular stress. People with high blood pressure, heart-rhythm disorders or taking stimulant or antidepressant medication should avoid it.

White willow bark (salicin)

People sensitive to salicylates or aspirin, with stomach ulcers or bleeding disorders, or taking blood thinners should avoid it⁸. Aspirin is a medicine and is not suitable in pregnancy or for children.

DMAA (1,3-dimethylamylamine)

DMAA is a potent pressor agent. Cases of cerebral haemorrhage have been reported in adults after using DMAA³.

Hordenine

Human safety data at supplement doses are lacking. It may interact with MAO inhibitors and other stimulants. Analyses of sports and weight-loss supplements have repeatedly found stimulants that were not declared, or quantities different from the label¹³¹⁴.

Octopamine and halostachine

These amines may raise heart rate and blood pressure, especially with caffeine and other stimulants.

Higenamine

As a β2-agonist, higenamine may raise heart rate and cause palpitations, and its safety at supplement doses has not been established⁶.

Yohimbine (yohimbe bark, rauwolscine)

A review of poison-centre cases found that adverse events with yohimbine products had more serious outcomes than average exposures, including rapid heart rate, anxiety, high blood pressure and agitation¹⁷. People with heart conditions, high blood pressure, anxiety disorders or taking antidepressants should not use yohimbine.

Huperzine A

As an acetylcholinesterase inhibitor, huperzine A can cause nausea, diarrhoea, sweating and a slow heart rate, and it may interact with medicines that affect acetylcholine or heart rate. Anyone taking medication or with heart, lung or digestive conditions should ask a doctor first.

Contains 1,3-dimethylamylamine (DMAA), a synthetic stimulant that is not authorised as a novel food in the EU and is on the WADA Prohibited List. Contains yohimbine. Isolated yohimbine is classified as a medicinal substance in several EU member states; its legal status depends on the country of sale.

Caffeine

Caffeine is permitted in EU foods and food supplements, subject to labelling rules. It is not on the World Anti-Doping Agency Prohibited List¹⁸.

Synephrine (bitter orange, Citrus aurantium)

Bitter orange extracts are used in EU food supplements under national rules, which differ between Member States¹⁹.

White willow bark (salicin)

Aspirin (acetylsalicylic acid) is a medicinal substance and is not permitted in food supplements in the EU²⁰. No health claim for this ingredient is authorised in the EU²¹; it is sold under national food-supplement rules¹⁹.

DMAA (1,3-dimethylamylamine)

DMAA is not authorised as food or as a food supplement ingredient in the EU²² and is prohibited in competition by the World Anti-Doping Agency¹³¹⁸.

Hordenine

Hordenine is not an authorised food supplement ingredient in the EU; its status depends on novel food rules²².

Octopamine and halostachine

They are not authorised food supplement ingredients in the EU²². Octopamine is prohibited in competition by the World Anti-Doping Agency¹⁸.

Higenamine

Higenamine is not an authorised food supplement ingredient in the EU²² and is prohibited at all times by the World Anti-Doping Agency as a β2-agonist¹⁴¹⁸.

Yohimbine (yohimbe bark, rauwolscine)

Yohimbine is a pharmacologically active substance. Its use in food is regulated under Regulation (EC) No 1925/2006 and national rules²³, and several EU Member States treat it as a medicinal substance²⁰.

Huperzine A

Huperzine A is a pharmacologically active substance. Its status as a food ingredient is not harmonised in the EU, and some Member States treat it as a medicinal substance²⁰²².